6.0 CENTRAL SUBWAY Construction Methods, IMPACTS, AND MITIGATION measures

This chapter of the SEIS/SEIR describes the construction techniques and schedules for building the Central Subway.  The locations along the alignment where each of the construction methods would be used and how each of the methods are incorporated into construction of various Project elements are also described.  Because the construction schedule would extend for 5.5 to 6 years, with an addition [begin deletion] al [end deletion] six months of pre-revenue testing, and temporary disruption around portals and stations represent the majority of impacts for the Project, this section has been created as a separate chapter to discuss impacts and mitigation measures related to construction for each environmental topic.

Temporary impacts from construction of the Central Subway Project are described for each Build Alternative and design option starting in Section 6.3.  The impacts discussion is organized by environmental topic in the same order as in Chapters [begin insertion] 3.0 [end insertion] [begin deletion] 4.0 [end deletion] and 5.0.  No construction impacts would occur for Alternative 1, No Project/TSM because no project-related construction is proposed.  Therefore, Alternative 1 will not be discussed further in this chapter.

6.1  Proposed Construction methods

The Central Subway requires a number of underground structures, including guideway tunnels, stations, tail tracks, rail crossovers, and emergency cross-passages. These structures would be constructed in a variety of geologic conditions, ranging from rock to soft ground, and would be located adjacent to existing structures and utilities that are sensitive to ground movements.  Available geologic information for the alternative Central Subway alignments indicates the tunnels would encounter highly variable conditions ranging from saturated sand, silt and clays to weathered and highly fractured sandstone and siltstone bedrock of the Franciscan Formation.  Mixed-face conditions (i.e., rock and soil in the excavation face) are expected where the tunnels transition into and out of the bedrock.  To deal with the different alignment and profile options and the varying geologic and groundwater conditions, several different tunnel construction methods are being considered, including excavation by Tunnel Boring Machine (TBM), cut-and-cover (C&C), and sequential excavation methods (SEM).  Another method, referred to as the Special Excavation Method (SXM), was introduced in the 1998 FEIS/FEIR.

Some of these excavation and ground support methods require the use of ground modification methods, such as dewatering, deep soil mixing, ground freezing, jet grouting, permeation grouting, compaction grouting, and compensation grouting.  Each of these construction methods is described below for the Central Subway Alternatives.

6.1.1 Tunnel Boring Machine (TBM) (Alternative 3 - Fourth/Stockton Alignment, Options A  and B)

A TBM consists of a rotating cutterhead within a cylindrical steel shell that is pushed forward along the axis of the tunnel while excavating the ground through the cutterhead.  The steel shield supports the excavated ground as required until the preliminary or final tunnel lining is built in the rear of the shield.  The shield is propelled using hydraulic jacks that thrust against the erected tunnel lining system.  The TBM is used in conjunction with a prefabricated ground support system, which most commonly consists of pre-cast concrete segments that are bolted and gasketed to form a watertight lining.

Pressure-face TBMs that are capable of exerting a balancing pressure against the tunnel face are used to control excavation rates and groundwater inflow, as well as to maintain stability of the tunnel face.  The two most common types of pressurized-face TBMs are earth pressure balance (EPB) machines and slurry shields.  Figure 6-1 shows a typical EPB TBM.  For the expected high groundwater and variable geologic conditions, both EPB and slurry machines would be well suited for construction of the Central Subway running tunnels.

After completion of TBM excavation and installation of the lining, the temporary rail is removed, the invert is cleaned, and a flat invert for the permanent rail fixation and a raised walkway are usually constructed as reinforced, cast-in-place concrete. The invert contains embedded pipes and inlets for track drainage.  Placement of invert concrete does not require a form, and can be placed continuously.

6.1.2 Cut-and-Cover (C&C) (Alternative 2 – Enhanced EIS/EIS Alignment and Alternative 3 - Fourth/Stockton Alignment, Options A and B)

The cut-and-cover method involves construction of a box frame structure within a trench excavation that is subsequently backfilled. In urban settings the cut-and-cover method requires utility relocation, traffic re-routing, and creates construction impacts in the form of noise, dust, and traffic, transit and business access disruption. 

Decking can be placed over the cut immediately following the first lift of excavation to reduce traffic disruption.  The decking is removed and the surface restored at the end of construction.  Figure 6-2 illustrates the placement of concrete decking on a cut-and-cover subway station.  Temporary excavation support walls (or shoring) are installed before significant excavation commences.  These walls must be supported with internal struts or tiebacks as the excavation is deepened to avoid instability and control settlement at the sides of the cut.  Depending upon the depth of excavation and the ground conditions the following methods of shoring would be used:

Figure 6-1

earth pressure balance tunnel boring machine

Source:  PB/Wong

· Cased secant piles - Cased secant piles are non-driven piles that can be used for ground support in soft ground and hard ground.  Secant pile walls are formed by constructing interlocked concrete piles reinforced with either steel rebar or beams.  Used extensively in dense population areas due to the minimal disturbance they cause to adjacent structures, secant pile walls are commonly used for shafts and stations in saturated soil conditions.  The steel reinforcement in the form of reinforcing bar or wide-flange sections can be dropped or vibrated into place.

· Soldier pile and lagging walls - Soldier pile wall construction is feasible in unsaturated or dewatered soils with sufficient stand-up time to allow some soil exposure prior to placement of lagging walls to hold back soils.  This method of construction can cause difficulties during excavation in loose sands that tend to ravel or soft clays that fast ravel or squeeze.  Soldier pile and lagging support is not watertight and requires dewatering below the groundwater table.  This construction method would be most applicable where compressible materials such as Bay Mud are not present since dewatering can generate excessive settlement adjacent to the walls. 

Figure 6-2

Cut-and-cover Tunnel Construction

Source:  PB/Wong

· Sheet pile walls - Sheet pile walls are watertight and do not require dewatering, although they cannot be driven where obstructions or hard materials are present in the soil profile.  Sheet piles can be driven to depths up to approximately 60 feet in dense sands and up to approximately 85 feet in soft to medium clays.  A disadvantage of this method is that it is not adaptable to utility crossings.  Like soldier pile and lagging walls, sheet pile walls would most likely be employed at the south end of the Central Subway alignment, where utility crossings do not preclude its use.

· Diaphragm slurry walls - Several types of diaphragm slurry walls are applicable to construction of the subway section of the Project.  Diaphragm walls have been constructed in virtually all soil types, but mainly in soft to medium stiff clays, saturated silts, and saturated, loose silty or clayey sands.  These walls provide a watertight support system like sheet pile walls and, in addition, provide greater wall stiffness, which helps to control settlement.  Construction of diaphragm walls also has the advantage of causing much less noise and vibration than driving sheet pile walls.  Diaphragm slurry walls are sometimes used as permanent walls within the cut.  As with sheet pile walls, diaphragm walls are not adaptable to utility crossings since all utilities crossed by the wall must be relocated.

· Soil-cement-mixed walls – Continuous soil-cement walls are installed underground using mechanical soil-mixing technology for the purposes of excavation support, ground water control and containment of contaminated soil.  The equipment for this purpose usually has multiple shaft augers to install a panel element consisting of multiple overlapped soil-cement columns.  The panels overlap each other to form continuous soil-cement walls.  A recent development uses large trench cutting equipment equipped with the chainsaw-like cutter, which moves horizontally while cutting and mixing in-situ soil with cement grout to form seamless soil-cement walls.  A narrow trench is excavated under bentonite slurry.  The excavation is completed to the final trench depth with the slurry acting as a stabilizing agent to keep the walls of the trench from collapsing.  Once the excavation of the trench has progressed to some point clear of the starting point, it is backfilled with a blended mixture of soil, bentonite slurry, dry bentonite and cement.  Backfill is placed in the trench after the excavation is completed by forming a slope of the mixed material that slumps down and displaces the liquid slurry forward.  The excavation proceeds at the same rate as backfilling, so that the distance between the excavator and the backfill placement point remains relatively constant.

Some form of internal bracing or tiebacks is required with each of the wall types discussed above. Internal bracing is the most commonly used support for narrow cut-and-cover excavations.  An alternative to internal bracing support is the use of tiebacks.  Tiebacks may be feasible for some elements of cut-and-cover construction on the Central Subway, but have several disadvantages.  Tiebacks may require additional right-of-way to extend anchors beyond the excavation line, which may not be possible where basements exist, and they generally are not economical for excavations less than 60 feet wide.

6.1.3 Sequential Excavation Method (SEM) - (Alternative 2 – Enhanced EIS/EIR Alignment and Alternative 3 - Fourth/Stockton Alignment, Options A and B)

The sequential excavation method (SEM, also known as NATM or New Austrian Tunneling Method) is a mined method of tunnel construction used worldwide for small to large openings in a variety of ground types ranging from rock to soil.  The objective of the method is to control deformations and thereby mobilize and maximize the self supporting capacity of the surrounding rock or soil.  The tunnel excavation is carried out in increments (headings or rounds) in numerical sequence (as shown in Figure 6-3), which are supported with sprayed concrete immediately after exposure, followed by installation of additional steel and shotcrete support elements until a safe stable opening is created.  SEM provides a

Figure 6-3

Tunnel Construction using Sequential Excavation Method (SEM)

Source:  PB/Wong

high degree of flexibility during construction and makes it possible to control virtually all kinds of ground conditions, thereby greatly reducing the risks of construction. 

After completion of the excavation and initial support, a waterproofing system is installed between the initial and the final lining.  The final lining, which can be either reinforced cast-in-place concrete or reinforced shotcrete, is then installed.

6.1.4 Special Excavation Method (SXM)  (Alternative 2 - Enhanced EIS/EIR Alignment)

The Special Excavation Method (SXM) illustrated in Figure 6-4 is a hybrid tunnel construction approach for a shallow tunnel profile developed by Dames & Moore for the 1998 FEIS/FEIR.^[1]  SXM combines elements of conventional cut-and-cover with mining procedures with the objective of reducing the surface impacts associated with conventional cut-and-cover.  An underground box is constructed to form an enclosure around the permanent underground structures.  Soil confined within the limits of the box is excavated by mined methods, followed by installation of a cast-in-place final lining for the guideway. 

The SXM method of construction requires continuous installation of ground support walls (shoring) using deep cement-soil mixing methods followed by installation of subsurface jet-grouted slabs above and below the guideway tunnels between the shoring, excavation of the contained soil between the jet grouted slabs and the shoring followed by construction of the cast-in-place permanent guideway structure.

Figure 6-4

Special Excavation Method (SXM) Concept Developed for the 1998 FEIS/FEIR

Source:  Dames & Moore, Special Excavation Methods for Central Subway, August 20, 1997

Installation of large-section, closely spaced, steel support beams and plates would be required to support the roof of the excavation beneath the jet grouted slab.  Heavy construction vehicles would be required to deliver these support elements to various locations along the alignment between the portals and Union Square Station.  Storage of construction materials would require temporary elimination of curb side parking.

SXM does not eliminate surface disruption to the same extent that mined or bored methods do. Construction of the soil-cement walls would require numerous utility relocations along the entire length of the walls, which run continuously down the streets. Heavy construction equipment would be required to mix the soil in-place to construct the walls and to install the steel soldier piles. In addition, the soil-cement process results in construction debris on the street surface, which must be contained and cleaned continuously.  

6.2 Description of Construction Methods for Build Alternatives

6.2.1 Enhanced EIS/EIR Alignment – Alternative 2

Construction of the Enhanced EIS/EIR Alignment would be accomplished using a combination of SEM, SXM and cut-and-cover techniques described in Section 6.1.  A summary of construction methods for the Enhanced EIS/EIR Alignment and the time-frame for performing the activities are presented in Table 6-1 and Figure 6-5.

Guideway Construction and Staging Areas – Alternative 2

A single tunnel structure would be constructed south of Moscone Station on Third and Fourth Streets using SXM methods.  The Third Street structure would extend from the northbound portal to Third and Harrison Streets and the single-tunnel structure on Fourth Street would extend approximately 2,500 feet between the southbound portal and the point where it would join the northbound guideway at Third and Harrison Streets.  The segment between Moscone Station and Union Square Station would require several transitions from vertically stacked to side-by-side tunnel.  The SXM construction method would be used for the stacked tunnels and cut-and-cover methods for the side-by-side shallow portion at Market Street.  The segment from Moscone Station to the Market Street Station covers a distance of 950 feet and transitions from a vertically stacked arrangement at Moscone Station to a side-by-side cut-and-cover configuration at Market Street Station.  The segment from Market Street Station to Union Square Station via Kearny and Geary is approximately 1,450 feet long and would be constructed using SXM.

The line segment between Union Square Station and Chinatown Station would be mined by SEM as a tall cavern, approximately 40 feet high, to accommodate vertically stacked guideway tunnels starting in the

Table 6-1

Summary of Guideway Construction Methods

Figure 6-5

Construction Durations for Alternatives 2, 3A and 3B

Source:  PB/Wong

vicinity of the Union Square Station and would transition to a side-by-side configuration, approximately 35 feet wide, over the 1,530-foot distance to Chinatown Station.  Excavation of this segment would commence at Union Square Station below Sutter Street and proceed north to Chinatown Station.  Excavated spoils would be hauled away from the Union Square Station.  The line segment north of Chinatown Station, comprised of the tail tracks and crossover, would consist of a twin-track tunnel approximately 35 feet wide by 575 feet long that would be mined from the Chinatown Station.

Stations Construction and Staging Areas – Alternative 2

Moscone Station, on Third Street between Howard and Folsom Streets, would be decked cut-and-cover construction staged from a primary off-street construction access shaft on Clementina Street.  See Figure 6-6 for approximate area of surface disruption during construction.  Cut-and-cover excavation of Moscone Station would require one lane of Third Street, to the south of Clementina Street and north of Tehama Street, to be temporarily closed to traffic for the duration of station construction (approximately 36 months) maintaining access to the Moscone Center Garage.  Although access to the truck ramps leading to the loading docks underneath the Moscone Convention Center and vehicle access to the Moscone Garage would be impacted during the shoring and decking stages.  Pedestrian access along Third Street between Howard and Folsom Streets and on Tehama Street would require protective cover for the entire duration of station construction.

Market Street Station, on Third Street south of Market Street, would also be decked cut-and-cover construction staged from a principal construction access shaft on Stevenson Street (see Figure 6-7).  Cut-and cover methods would be used to construct a pedestrian connection tunnel from the Market Street Station to the BART/Muni Metro Montgomery Street Subway Station in the Market Street sidewalk. 

Union Square Station would be constructed on Stockton Street between Post and Geary Streets using decked cut-and-cover methods (see Figure 6-8).  Staging areas for construction would occupy the westerly sidewalk and traffic lanes on Stockton Street east of Union Square between Post and Geary Streets.

Chinatown Station would be mined using SEM methods for the platform cavern, crossover and tail track tunnel; all staged from the off-street station access shaft (see Figure 6-9).  This shaft would be decked over and used as a headhouse for access to subsurface excavation and for spoils removal.  It would later be fitted out as the station entrance.  All station structural work, architectural finishes, and mechanical systems would be installed from the surface through the same off-street headhouse shaft.  Stockton Street would be used to access the station construction site for hauling materials, equipment, and spoils.

Figure 6-6

Alternative 2 – Moscone Station

Area of Surface Disturbance During Construction

Figure 6-7

Alt. 2 Market Street Station

Area of Surface Disturbance During Construction

Figure 6-8

Alt. 2 Union Square Station

Area of Surface Disturbance During Construction

Figure 6-9

Alt. 2 Chinatown Station

Area of Surface Disturbance During Construction

Utility Relocations – Alternative 2

The SXM method of construction requires relocation of all utilities ahead of the guideway construction and/or placement of utilities in utility corridors where feasible–an effort that will take about 24 months (see Figure 6-5).  Utility relocation for the subway would occur on Fourth Street, between Brannan and Harrison Streets; on Harrison Street, between Third and Fourth Streets; on Third Street, between Brannan and Market Streets; along Geary Street, between Market, Kearny, and Stockton Streets; and on Stockton Street between Geary and Sutter Streets.

At Mission and Third Streets, the subway profile conflicts with the 8‑foot diameter North Point Main sewer line, which carries storm drain runoff and sanitary sewer flows.  Several options are possible, including abandoning or rerouting the sewer line or installing a siphon and pump station to force the effluent under the subway.  All options would occur within the public right-of-way.  Installation of the siphon or rerouting the sewer line would require the longest pre-construction period, up to approximately 18 months.  Curb parking in each block requiring utility diversions would need to be temporarily eliminated to accommodate traffic flow.

Cut-and-cover excavation of Market Station would require one lane of Third Street, from Stevenson Street to Jessie Street, to be closed to traffic for the duration of station construction (about 36 months).  This would impact, though not entirely eliminate, access to Stevenson Street and the Hearst Parking Garage.  Pedestrian access along both sidewalks on Third Street between Mission and Market Streets would require protective cover for the entire duration of station construction. 

Cut-and-cover excavation of Union Square would require two lanes of Stockton Street, from Post Street to just south of Maiden Lane,  to be closed to traffic for the duration of station construction (48 months).  Access to the Union Square Parking Garage on Geary Street would not be obstructed.  Pedestrian access along the west sidewalk on Stockton Street between Geary and Post Street would be closed for the entire duration of station construction. 

Spoils Handling – Alternative 2

Guideway excavation would proceed in a northerly direction from the portals south of Bryant Street towards Union Square.  As guideway excavation proceeded, muck would be transported through the constructed portions of the guideway to each portal before being hauled off-site for permanent disposal.  [begin deletion] The south portal on Fourth Street would be the primary truck loading site.  Trucks carrying materials from the portal site would be routed directly to the I-80 freeway for disposal sites to be determined by the contractor.  Truck travelling east on I-80 would travel south on Fourth Street, west on Brannan Street, and [end deletion]

[begin deletion] north on Fifth Street to the I-80 eastbound on-ramp.  Trucks travelling westbound on I-80 (southbound) would travel south on Fourth Street, east on Brannan Street, north on Third Street, and west on Harrison Street to the I-80 westbound on-ramp.  The southbound trucks from the Third Street portal would follow this same route.  The trucks from the Third Street portal going east on I-80 would continue west on Harrison Street, turning south on Fifth Street to the I-80 eastbound on-ramp. [end deletion]

Spoils from excavation of the Chinatown Station, the crossover cavern and the tail track tunnels would be removed by way of the Chinatown Station access shaft and hauled off-site for disposal. [begin deletion]   Trucks from Chinatown would travel on Stockton Street to eastbound Broadway, south on Battery Street, and continuing south on First Street to the I-80 eastbound freeway-ramp or continuing west on Harrison Street to the I-80 westbound on ramp. [end deletion]

Spoils generated from excavation of the Union Square Station and the guideway tunnels north of Union Square would be

hauled to the surface at Union Square and hauled off-site for disposal. [begin deletion]   Trucks from the Union Square Station construction site would travel south on Stockton Street continuing on Fourth Street to the I-80 eastbound on-ramp or turning west on Harrison Street and south on Fifth Street to the I-80 eastbound on-ramp. [end deletion]

Spoils generated from excavation of Market Street Station and Moscone Station would be hauled to the surface at Stevenson and Clementina Streets, respectively, before being hauled off-site for permanent disposal. An estimated 524,000 cubic yards of spoils would be disposed of for Alternative 2, resulting in approximately 8 truck trips per day during the 4.5 year construction for the guideway and 8 to 10 daily truck trips from each station during the station excavation periods. [begin deletion]   Trucks from the Moscone and Market Street Stations construction sites would travel south on Fourth Street to the I-80 eastbound on-ramp or take Fourth Street, west on Harrison, and south on Fifth Street to the I-80 westbound on-ramp. [end deletion]

Construction Sequencing and Duration – Alternative 2

The 1998 FEIS/FEIR staged the subway construction in two phases, the south of Market Street segment first followed by the north segment from Market Street to Chinatown.  For the Enhanced EIS/EIR Alignment, it is assumed that construction of both segments would be done concurrently thereby significantly reducing the overall construction schedule.  Construction of the Enhanced EIS/EIR Alignment would be accomplished in a single phase.  Refer to Figure 6-5 for a summary of construction activities and the schedule.

Because of the intensity of utility relocations required to enable construction of the guideway tunnels and station by SXM and cut-and-cover methods between Brannan and Post Streets, the first 24 months of the Enhanced EIS/EIR Alignment would be devoted to pre-construction activities and relocation of impacted utility lines, and trolley bus routes on Fourth, Third, Harrison, Market, and Geary Streets.  At Mission and Third Streets, the guideway alignment would require relocation of the eight-foot North Point sewer line which carries storm drain runoff and sanitary flows or installation of a siphon.

The subsequent 40 months would focus on construction of the portals on Third and Fourth Streets, the cut-and-cover stations at Moscone and Market Street, and the guideway tunnels between these points.  Following diversion of utilities and transit lines, Fourth Street between Brannan and Harrison Streets, Harrison Street between Fourth and Third Streets, and Third Street between Brannan and Market Streets would require at least two lanes closures plus temporary loss of curb parking for installation of the jet grouted slabs above and below the guideway tunnels and for installation of the soil cement or secant pile ground support walls.  Sequential lane closures of Market, Kearny, and Geary Streets would be required

to allow the cut-and-cover and SXM sections of the guideway tunnel to be constructed between Moscone Station and Union Square Station.

The SXM method would require sequential movement of construction activities, block by block.  When the jet grouting installation in one block is completed, the drilling rigs and grouting equipment would be moved to the next block and the piling rigs and soil cement placement equipment would move in behind it.  The work would be staged to coordinate both sets of activities.  The closure of at least two lanes for

any two consecutive blocks on Third Street between Harrison Street and Market Street would be required for periods of at least four months.

The construction of the Union Square Station would start six months in advance of the Moscone and Market Street Stations.  A typical sequence of activities for the construction of the Union Square station and the estimated durations of the activities is presented in Figure 6-10.  Excavation of the guideway tunnels between the Union Square and Chinatown Stations would commence north from the Union Square Station box using SEM.  Spoils from excavation of this segment of the guideway tunnels would be hauled off-site from Union Square.

Excavation, ground support and structural elements for guideway tunnels and stations for the Enhanced EIS/EIR Alignment would require approximately 66 months (5.5 years) to complete (refer to Figure 6-5).

6.2.2 Fourth/Stockton Alignment Option A – Alternative 3A

Construction of the Fourth/Stockton Alignment Option A would be accomplished using a combination of SEM, TBM and cut-and-cover techniques as described in Section 6.1.2.  A summary of construction methods and schedule for this alternative are presented in Table 6-1 and Figure 6-5.

Guideway Construction and Staging Areas – Alternative 3A

The majority of the subway segment between the portal at Fourth and Brannan Streets and Chinatown Station would be constructed by TBM as twin, approximately 20-foot diameter, single-track bores.  The segment north of Chinatown Station would consist of a crossover and twin tail tracks in a single SEM cavern that would extend approximately 600 feet north of the station cavern. 

The Fourth/Stockton Alignment Option A could be constructed using one or two TBMs.  As originally conceived, the construction method proposed for this alternative used a single TBM launched at the tunnel construction shaft located on Fourth Street adjacent to the I-80 Freeway and recovered from the off-street access shaft at Chinatown Station.  After completing the northbound guideway tunnel, the TBM would be transported back to the tunnel construction shaft and re-launched to excavate the southbound guideway tunnel.  If two TBMs were to be used, both machines would be launched from the tunnel construction shaft.

The tunnel construction shaft would be located on Fourth Street [begin insertion] between [end insertion] [begin deletion] , just south of [end deletion] Perry [begin deletion] Street [end deletion] [begin deletion] , between Harrison [end deletion] and Bryant Streets.  The guideway tunnel construction staging areas would occupy the area beneath I-80, to the west of Fourth Street.

Figure 6-10

Construction Activities and Durations

for union square and union square/market street Stations

Source:  PB/Wong

Cut-and-cover methods would be used for construction of the approximately 1,100 foot subway segment between the tunnel construction shaft and the portal.  Staging areas for the cut-and-cover tunnel would consist of decked-over portions of the street and would generally follow construction as it proceeded south from the tunnel construction shaft.

If the North Beach Construction Variant is adopted, the tail track would be constructed by the extended TBM tunnel and would include a mined cross passage; otherwise it would be mined as a single, twin-track cavern using SEM. 

For support of TBM tunnel construction, the I-80 tunnel construction shaft, including the cut-and-cover TBM launch box immediately north of the shaft, would be the primary staging area.  For the North Beach Construction Variant, the TBM retrieval shaft located on Columbus Avenue would be used periodically for night time delivery and removal of materials.

Stations Construction and Staging Areas – Alternative 3A

Moscone Station would be decked cut-and-cover construction located on Fourth Street between Howard and Folsom Streets with station entrances north of Howard Street.  See Figure 6-11 for approximate area of surface disturbance during station construction.  Construction of Moscone Station would require two lanes of Fourth Street to be closed to traffic for approximately 15 months for installation of the shoring and decking.  Although not entirely eliminated, access to the truck ramps leading onto Fourth Street from the Moscone Convention Center loading docks would be temporarily disrupted during placement of shoring and decking for the Moscone Station.  Pedestrian access along the west side of Fourth Street between Howard and Folsom Streets would be impacted during installation of shoring.

[begin insertion] Clementina Street and the adjacent [end insertion] [begin deletion] The [end deletion] lot [begin deletion] at the southwest corner of Clementina and Fourth Streets [end deletion] (14,800 square feet) presently occupied by a gas station would serve as the staging area for the Moscone Station and the temporary construction shaft. 

Union Square/Market Street Station would be a combination of decked cut-and-cover construction and an SEM mined cavern located on Stockton Street between Geary Boulevard and Market Street (see Figure 6-12).   The cut-and-cover sections of Union Square/Market Street Station would require at least two lanes of Stockton Street to be closed to traffic for approximately 10-12 months for installation of shoring and decking.  Ellis Street would be reduced to one lane of traffic to accommodate the construction staging area.  Pedestrian access along both sidewalks on Stockton Street between Geary Street and Market Streets would require protective cover for the entire duration of secant pile shoring installation.

Figure 6-11

Alt. 3A Moscone Station

Area of Surface Disturbance During Construction

Figure 6-12

Alt. 3A Union Square/Market Street Station

Area of Surface Disturbance During Construction

Union Square/Market Street Station would require two primary staging areas, one on Ellis Street (4,400 square feet) for the South Concourse and one on Stockton Street (7,600 square feet) adjacent to Union Square, which would support construction of the North Concourse.  The westerly sidewalk and traffic lanes on Stockton Street between Post and Geary Streets would be closed for about 36 months.  Other temporary closures of Stockton Street would be required and would be done at night when possible. Construction of the north and south cavern access shafts would require the temporary use of at least two lanes of Stockton Street and would need to accommodate a crane and trucks for muck hauling.  After construction of the shaft, intermittent use of Stockton Street would be needed for removal of the microtunneling machines that would be used for the platform cavern pipe canopy.

The Chinatown Station would be a mined excavation.  SEM methods would be used for excavation of the platform cavern, crossover and tail track tunnels, and all operations would be conducted from the off- street station access shaft (see Figure 6-13).  This shaft would be decked over and used as a headhouse for access to subsurface excavation and for spoils removal.  It would later be fitted out as the station entrance.  All station structural work, architectural finishes, and mechanical systems would be installed from the surface through the same off-street headhouse shaft.  Stockton Street would be used to access the station construction site for hauling materials, equipment, and spoils.  A construction barrier wall on the eastside of the site, about 20 to 30 feet high, would protect the adjacent alley and playground (Willie “Woo Woo” Wong) from construction noise, dust, and visual disturbance.

The off-street portion of the station access/headhouse shaft would be partially decked over and used as a staging area (approximately 4,700 square feet).  A crane would be required for station and shaft excavation and construction.  Curb parking on Stockton Street would be used to accommodate trucks.  Temporary (one to two weeks) use of a higher capacity crane would be required to hoist the TBMs if they are retrieved through the Chinatown access shaft.

Utility Relocations – Alternative 3A

Relocation of utilities ahead of station construction would be required on Stockton Street between Post Street and Market Street; on Fourth Street between Howard and Folsom Streets; and on Fourth Street between Harrison and Townsend Streets for the construction shaft, the cut-and-cover construction south of the tunnel construction shaft and the portal.  These utility relocations would take about 12 months.

Curb parking in each block along the utility diversions would be eliminated during this work to accommodate traffic flow around the work area.

Figure 6-13

Alt. 3A Chinatown Station

Area of Surface Disturbance During Construction

Spoils Handling – Alternative 3A

Tunnel excavation by TBM would proceed in a northerly direction from the tunnel construction shaft towards the Chinatown Station.  Muck produced by the TBMs would be transported through the tunnels back to the tunnel construction shaft and stockpiled before being hauled off-site for permanent disposal.  Spoils generated from the excavation of each of the stations, Moscone Station, Union Square/ Market Street Station and Chinatown Station, the crossover cavern and the tail track tunnels would be hauled to the surface through off-street shafts at each of the station locations before being hauled off-site for permanent disposal.  Spoils generated from excavation of the segment between the tunnel construction shaft and the portal by cut-and-cover method would be loaded when excavated as the construction progressed and hauled off-site for permanent disposal.  An estimated 489,000 cubic yards of spoils would be disposed of for Alternative 3A, resulting in approximately 18 truck trips per day during the 2.5-year guideway excavation period; 13 daily truck trips during the 2.0-year excavation period for the Moscone Station; and about 7 trips per day during the Union Square/Market Street Station (3.0 years) and Chinatown Station (2.5 years) excavation periods.

[begin deletion] The south portal on Fourth Street would be the primary truck loading site.  Trucks carrying materials from the portal site would be routed directly to the I-80 freeway for disposal sites to be determined by the contractor.  Trucks travelling east on I-80 would travel south on Fourth Street, west on Brannan Street, and north on Fifth Street to the I-80 eastbound on-ramp.  Trucks travelling westbound on I-80 (southbound) would travel south on Fourth Street, east on Brannan Street, north on Third Street, and west on Harrison Street to the I-80 westbound on-ramp.  Trucks from the from the Moscone Street Station construction site would travel south on Fourth Street to the I-80 eastbound on-ramp or continue west on Harrison Street and south on Fifth Street to the I-80 westbound on-ramp.  Trucks from the Union Square/Market Street Station construction site would travel south on Fourth Street then follow the same route south as the trucks from the Moscone Station.  Trucks from Chinatown would travel on Stockton Street to eastbound Broadway, south on Battery Street, and continuing south on First Street to the I-80 eastbound freeway-ramp or continuing west on Harrison Street to the I-80 westbound on ramp. [end deletion]

If the North Beach Tunnel Construction Variant is adopted, spoils generated from excavation of the TBM retrieval shaft on Columbus Avenue would be hauled to the surface at the shaft location before being hauled off-site for permanent disposal.  [begin deletion] An estimated 3,200 cubic yards of spoils would be removed at the retrieval shaft on Columbus Avenue resulting in an estimated five truck trips per day during the six-month long excavation period.  Approximately 20 truck trips would be required to remove the tunnel boring machines. [end deletion]

[begin deletion] Eastbound trucks hauling debris from the TBM extraction pit would go southeast on Columbus Avenue, east on Washington Street, south on Battery Street, and continue south on First Street to the I-80 eastbound on-ramp.  Southbound trucks would follow the same route continuing west on Harrison Street to the I-80 westbound on-ramp. [end deletion]

Construction Sequencing and Durations – Alternative 3A

Construction of the Fourth/Stockton Alignment Option A would be accomplished in a single phase.  A summary of construction activities and schedule for this alternative is presented in Figure 6-5.

The first 15 months of the Alternative 3A pre-construction activities would include relocation of existing utility lines and impacted transit services, and excavation of the tunnel construction shaft beneath I-80 between Harrison and Bryant Streets.  Procurement, delivery, and assembly of the TBM would take approximately 12 months.  Guideway tunnels would commence from the tunnel construction shaft at Fourth and Harrison Streets northward towards the Chinatown Station.  The TBM would advance at approximately 30 feet per day. Removal of excavated spoils and delivery of construction materials for the guideway tunnels would primarily occur at the tunnel construction shaft.   Station shells at Moscone Station and Union Square/Market Street Station would be excavated down to below track level in advance of the TBM reaching those locations so that the machine can be “walked” through the station and re-launched at its north end.  The platform cavern at Chinatown station would be excavated in advance of the TBM reaching that location to enable the machine to be recovered from the off-street access shaft and transported back to the tunnel construction shaft and relaunched to excavate the other guideway tunnel.

Construction of the guideway tunnels would take approximately 40 months using a single TBM.  If two TBM were used to excavate the tunnels simultaneously, there would be approximately one month lag between the two machines being launched and the construction duration would be shortened to approximately 18 months (refer to Figure 6-5).  At the end of guideway (tunnel) construction the TBM cutterhead would be retrieved through the Chinatown Station headhouse, an approximately one week effort.  The trailing sections of the TBM would be pulled back through the tunnel to the construction shaft.

If the North Beach Tunnel Construction Variant is adopted, the TBMs would be “walked” through the SEM mined platform and station caverns at the Chinatown station and re-launched and driven to North Beach and recovered from a shaft located in the middle of Columbus Avenue, rather than from the Chinatown Station headhouse.  Retrieval of the TBM would take about one week at this location.  TBM tunneling would not require any surface work or lane closures other than at the TBM recovery shaft on Columbus Avenue.  The shaft construction on Columbus Avenue is estimated to take approximately six months.

Moscone Station and the construction access shafts at the Union Square/Market Street Station would require temporary lane closures for a period of 10 and 12 months on Fourth Street between Folsom and Howard Streets and on Stockton Street between Ellis and Post Streets for installation of the shoring systems.  This would occur before the streets are fully decked over, at which point excavation of the stations would continue underground and spoils or materials would be delivered through access points on Clementina and Ellis Streets and adjacent to Union Square between Post and Geary Streets (refer to Figure 6-10).  During installation of the secant piles used for shoring, the sidewalks would be either closed to pedestrians [begin deletion] (only on segments that do not provide direct access to adjacent buildings) [end deletion] or protective barriers erected to separate the public from the construction activities.  After the decking is completed all lanes would be reopened to traffic, however truck traffic required for hauling of excavated spoils and delivery of construction materials would be necessary at each of these locations for the full duration of construction.

Construction of Chinatown Station and the adjacent cross-over and tail track tunnel would be carried out from an off-street shaft and is scheduled to take approximately 54 months.  With the exception of short periods of time when large equipment is being delivered to the station or when the TBMs are being retrieved from the shaft, no lane closures on Stockton Street in Chinatown are planned for construction of the station.  However, truck traffic required for hauling of excavated spoils and delivery of construction materials would be necessary for the full duration of construction, occupying the curb-side lane.

6.2.3 Fourth/Stockton Alignment Option B – Alternative 3B

Construction of the Fourth/Stockton Alignment Option B would be accomplished using a combination of SEM, TBM and cut-and-cover techniques as described in Section 6.1.2.  A summary of construction methods and schedule for this alternative are presented in Table 6-1 and Figure 6-5.

Guideway Construction and Staging Areas – Alternative 3B

The Fourth/Stockton Alignment Option B assumes the use of two TBMs for construction of the guideway tunnels, launched in parallel from the tunnel construction shaft and recovered from the access shaft at Chinatown Station, or, if the North Beach Construction Variant is adopted, from a TBM retrieval shaft located on Columbus Avenue.

The underground guideway segment between Harrison Street and the Chinatown Station would be constructed by TBM as twin, approximately 20-foot diameter, single-track bores.  The guideway segment from the Tunnel Construction Shaft to Moscone Station includes approximately 240 feet of twin box cut-and-cover tunnel that is used as part of the tunnel construction shaft for erecting and launching the TBMs.  The guideway segment between Moscone Station and Union Square/Market Street Station is approximately 1,800 feet long and includes one mined (SEM) cross passage with a sump pump at the low point in the profile.  The segment between Union Square/Market Street and Chinatown Station is approximately 2,500 feet long and includes a mined (SEM) crossover cavern and three mined (SEM) cross passages for emergency egress between the twin bored tunnels. 

The guideway segment, which extends 200 feet north beyond the Chinatown Station platform cavern, comprises the tail track tunnels.  If the North Beach Construction Variant is included, the construction methods would be the same as described under Alternative 3A.

Stations Construction and Staging Areas – Alternative 3B

Moscone Station would be located on Fourth Street between Howard and Folsom Streets and also would use a decked cut-and-cover construction approach.  See Figure 6-14 for approximate area of surface disturbance during station construction.  Clementina Street and the adjacent lot (14,800 square feet) presently occupied by a gas station would serve as the staging area for the Moscone Station and the temporary construction shaft. 

Cut-and-cover excavation of Moscone Station would require two lanes of Fourth Street to be closed to traffic for approximately 10 to 12 months for installation of the shoring and decking.  Although not entirely eliminated, access to the truck ramps leading onto Fourth Street from the Moscone Convention

Figure 6-14

Alt. 3B Moscone Station

Area of Surface Disturbance During Construction

Center loading docks would be temporarily disrupted during placement of shoring and decking for the Moscone Station.  Pedestrian access along the west side of Fourth Street between Howard and Folsom Streets would be impacted during installation of shoring.

Union Square/Market Street Station, located on Stockton Street between Geary and Ellis Streets, would be constructed using a decked cut-and-cover approach for the entire length of the station (refer to Figure 6-15). Union Square/Market Street Station would require at least two lanes of Stockton Street to be closed to traffic for installation of shoring and decking (about 10 to 12 months).  During installation of shoring for the platform section of the station, there may be a need to shut down Stockton Street to traffic completely for a period of six to eight months.  Ellis Street would be reduced to one lane of traffic to accommodate the construction staging area.  Pedestrian access along both sidewalks on Stockton Street between Geary Street and Market Street would require protective cover for the entire duration of secant pile shoring installation.

Two primary staging areas would be required, one on Ellis Street (5,000 square feet) to support construction of the South Concourse, the main platform box, and the emergency vent ducts that extend west under Ellis Street to the Ellis/O’Farrell Garage, and one on Stockton and Geary Streets (8,000 square feet), which would support construction of the North Concourse and the reconstruction of the southeast corner of Union Square to serve as the north station entrance.

The Chinatown Station at Stockton and Washington Streets would be constructed entirely by mined (SEM) methods from an off-street access shaft similar in approach, but different in dimensions and general layout from the Chinatown Station configurations developed for the Enhanced EIS/EIR and Fourth/Stockton, Option A Alternatives (see Figure 6-16).  All station headhouse structural work, architectural finishes, and mechanical systems would be installed from the surface through the off-street shaft.

The off-street portion of the station access/headhouse shaft would be partially decked over and used as a staging area (approximately 10,000 square feet).  A crane would be required for station and shaft excavation and construction.  Curb parking on the west side of Stockton Street would be used to accommodate trucks.  Temporary (one to two weeks) use of a higher capacity crane would be required to hoist the TBMs if they are retrieved through the Chinatown access shaft.

Utility Relocations – Alternative 3B

Relocation of utilities ahead of station construction would be required on Stockton Street between Post Street and Market Street; on Fourth Street between Howard and Folsom Streets; and on Fourth Street

Figure 6-15

Alt. 3B Union Square/Market Street Station

Area of Surface Disturbance During Construction

Figure 6-16

Alt. 3B Chinatown Station

Area of Surface Disturbance During Construction

between Harrison and Bryant Streets for the construction shaft and the portal.  These utility relocations will take about six months if carried out concurrently in each location.  Curb parking in each block impacted by the utility diversions would be temporarily eliminated to accommodate traffic flow.

Spoils Handling – Alternative 3B

Similar to Alternative 3A described above, tunnel excavation by TBM would proceed in a northerly direction from the tunnel construction shaft towards Chinatown Station.  Muck produced by the TBMs would be transported through the tunnels back to the tunnel construction shaft at I-80 and Harrison and Bryant Streets and stockpiled before being hauled off-site for permanent disposal. Spoils generated from the excavation of each of the stations, Moscone, Union Square/Market Street and Chinatown, the crossover cavern and the tail track tunnels would generally be hauled to the surface through off-street shafts at each of the station locations before being hauled off-site for permanent disposal.  An estimated 637,000 cubic yards of spoils would be generated by Alternative 3B, resulting in an estimated 23 truck trips per day during the 2.0-year excavation period for the guideway; 25 truck trips per day during the 1.0-year excavation period for Moscone Station; 20 daily truck trips during the 2.0-year excavation period of the Union Square/Market Street Station; and 9 daily truck trips during the 2.0-year excavation period for the Chinatown Station.

If the North Beach Tunnel Construction Variant is adopted, spoils generated from excavation of the TBM retrieval shaft on Columbus Avenue would be hauled to the surface at the shaft location before being hauled off-site for permanent disposal.  [begin deletion] An estimated 3,200 cubic yards of spoils would be removed at the retrieval shaft on Columbus Avenue resulting in an estimated five truck trips per day during the six-month long excavation period.  Approximately 20 truck trips would be required to remove the tunnel boring machines. [end deletion]

[begin deletion] The haul routes for the portal and the station construction sites would be the same as described for Alternative 3A. [end deletion]

Construction Sequencing and Durations – Alternative 3B

Construction of the Fourth/Stockton Alignment Option B would be accomplished in a single phase.  A summary of construction activities and schedule for this alternative are presented in Figure 6-5.

The first 18 months of the Fourth/Stockton Alignment Option B pre-construction activities would include relocation of existing utility lines and impacted transit services, and excavation of the tunnel construction shaft beneath I-80 at Harrison and Bryant Streets.  Excavation of the guideway tunnels would commence

from the tunnel construction shaft northward towards Chinatown Station and would commence approximately 18 months after start of construction.  The TBMs would advance at approximately 30 feet per day.  Removal of excavated spoils and delivery of construction materials for the guideway tunnels would occur at the tunnel construction shaft.  Two options are possible for sequencing the TBM excavation with the station excavation: 1) the TBMs would be allowed to proceed first followed by the station excavation; or 2) the station shells at Moscone Station and Union/Square Market Street Station

would be excavated down to below track level in advance of the TBM reaching those locations so that the TBM could be “walked” through the stations and relaunched.  The platform cavern at Chinatown Station would be excavated in advance of the TBM reaching that location to enable the machine to be recovered from the off-street access shaft.  Construction of the guideway tunnels with two TBMs would take approximately 18 months.  At the end of guideway (tunnel) construction the TBM cutter head would be retrieved through the Chinatown Station headhouse, an approximately one week effort.

If the North Beach Tunnel Construction Variant is adopted, the TBM would be “walked” through the SEM mined platform and station caverns at Chinatown Station, driven to North Beach, and recovered from a shaft located in the middle of Columbus Avenue rather than from the Chinatown Station headhouse.  Retrieval of the TBM cutter head would also take about one week at this location.  TBM tunneling would not require any surface works or lane closures other than at the TBM recovery shaft on Columbus Avenue.  The shaft construction is estimated to take approximately six months.

Moscone Station and Union Square/Market Street Station would require lane closures for 10 to 12 months on Fourth Street between Folsom and Howard Streets and on Stockton Street between Ellis and Geary Streets, respectively.  This would occur before the streets are fully decked over, at which point excavation of the stations would continue underground and spoils or materials would be delivered through access points on Clementina and Ellis Streets.  During installation of the secant piles used for shoring, the sidewalks would be either closed to pedestrians or protective barrier erected to separate the public from the construction activities.  After the decking is completed all lanes would be reopened to traffic, however truck traffic required for hauling of excavated spoils and delivery of construction materials would be necessary at each of these location for the full duration of construction.

The north entrance and station concourse of the Union Square/Market Street Station is located adjacent to Union Square on the corner of Stockton and Geary Streets.  Temporary traffic diversions and a lane closure on Geary Street would be required for a period of approximately six months to install the shoring and decking. 

Construction of the Chinatown Station, crossover tunnel, and tail track tunnel would be carried out from an off-street shaft and is scheduled to take approximately 48 months. With the exception of short periods of time when large equipment is being delivered to the station or when the TBMs are being retrieved from the shaft, no lane closures on Stockton Street in Chinatown are planned for construction of the station. Truck traffic planned for hauling of excavated spoils and delivery of construction materials would be necessary for the full duration of construction. 

6.3 Construction impacts and mitigation for transportation

6.3.1 transit

Alternative 2 – Enhanced EIS/EIR Alignment

This alternative would result in the greatest surface disruption during the construction period due to the nature of the SXM construction methods.  This alternative requires a longer and more extensive utility relocation process and a greater degree of construction activity at street level.

Temporary transit impacts (transit delays and rerouting) would occur off and on over an estimated 5.5 year period along King, Third, Fourth, Harrison, Kearny, Geary, and Stockton Streets.  During construction of the tunnels between Union Square and the portals between Brannan and Bryant Streets, at least one lane of traffic would be temporarily closed.

During construction at the Moscone and Market Street Stations and at the portals, at least one lane of traffic would need to be temporarily closed on Third and Fourth Streets for approximately 36 months.  Congested traffic conditions would occur during both commute and non-commute periods, resulting in potential disruption to the bus routes operating on these streets.  During the construction of the crossing of Market Street there would be disruption to the F-Line service requiring bus service to replace the F-Line. 

For 12 to 18 months during the 48 month construction period for the Union Square Station, there would be times when only one traffic lane would be open on Stockton Street between Geary and Sutter Streets.    For short durations there may be a need to shut down Stockton Street to traffic completely.  [begin insertion] Although it is not feasible to [end insertion] [begin deletion] Temporary [end deletion] re-rout [begin insertion] e [end insertion] [begin deletion] ing of [end deletion] the 30-Stockton and 45-Union/Stockton electric trolley bus line [begin insertion] s [end insertion] to alternative streets [begin deletion] during the [end deletion] [begin insertion] for the entire [end insertion] construction [begin deletion] period (six to eight months) [end deletion] [begin insertion] duration, temporary re-routing of these lines [end insertion] may be required.  Also a lane of Geary Street between Stockton and Market Streets, would be closed down for three to six months during the construction period, but bus service would be maintained.

During construction at the Chinatown Station, closure of one lane of traffic on Stockton Street may occur for short periods of time (one to three days) potentially disrupting transit service.

The increased congestion on King, Third, Fourth, Harrison, Kearny, Geary, and Stockton Streets would also lead to disruption of the transit service on these routes, resulting in an adverse impact on transit.

Mitigation Measures

To reduce some of the congestion that would result adjacent to construction of the Enhanced EIS/EIR Alignment, DPT would develop detour routes for non-transit traffic.  Use of alternative routes by non-

transit vehicles would reduce the level of congestion for all traffic, including buses along streets under

construction for the Project.  DPT would try to limit traffic along construction routes to transit, local deliveries, and construction vehicles only, with appropriate signing and traffic control personnel.

Re-routing the 30-Stockton and the 45-Union/Stockton trolley coaches would require moving the existing overhead wires to allow the trolley buses to reach lanes not presently served, construction of new overhead wires, or temporary substitution of motor coaches for the trolley coaches [begin deletion] ; a cost that is included in the project cost estimates.  Use of auxiliary power units (APUs) may be feasible for limited lengths traveling downhill on Stockton Street. [end deletion]   [begin insertion] Moving the overhead wires would add substantial cost to the Project.  Given the length of the construction and the length of travel, and the congestion in which the buses would have to maneuver, use of the auxiliary power units (APUs) would not be feasible for the buses to travel off-wire. [end insertion]

In general it is preferable to have all buses adhere as close as possible to their existing routes.  Muni will monitor the performance of bus lines affected during construction, and if necessary increase the number of buses to provide reliable service.  MTA will provide signing related to transit changes in Chinese as well as English.  [begin deletion] MTA will coordinate with BART to develop public outreach and other programs to minimize impacts to transit riders during construction. [end deletion]

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Transit impacts for the Fourth/Stockton Alignment Option A would be less than for Alternative 2 as the use of a TBM for tunnel excavation would reduce the level of surface disruption.  At the tunnel construction shaft, [begin deletion] Muni [end deletion] buses would be rerouted to the west side of Fourth Street between Bryant and Harrison Streets during installation of the tunnel construction shaft and cut-and-cover sections between Bryant and Townsend Streets.  As road decking is completed, buses would return to the east side of the street.  The two west lanes of Fourth Street between Bryant and Harrison Streets would remain closed for the duration of the construction of the guideway tunnels.

[begin deletion] Excavation of the construction shaft under the I-80 freeway between Bryant and Harrison Streets would also impact Golden Gate Transit bus operations under Alternative 3A.  Buses will use Harrison, Fourth, and Perry Streets to enter the Transbay Terminal mid-day bus storage facility that is proposed for the site between Perry and Stillman Streets, east of Fourth Street.  Generally buses would be entering the proposed Transbay Terminal bus layover facility after the morning peak commute period and exiting the site before the afternoon peak commute period (3 p.m.).  The reduction in lanes on Fourth Street during the construction period would temporarily affect access to the bus storage facility. [end deletion]

The two westerly lanes of traffic on Fourth Street, between Howard and Folsom Streets, would be closed for approximately four months during installation of the shoring at the Moscone Station.  The bus stop at the southwest corner of the Fourth and Howard Streets intersection would need to be temporarily relocated during this period.

At the Union Square/Market Street Station, Stockton Street would be reduced to two lanes between Post and Geary Streets and one lane between Geary and Ellis Streets.  Overhead trolley lines for the 30-Stockton and the 45-Union/Stockton lines would need to be [begin insertion] removed [end insertion] [begin deletion] temporarily relocated for a period of six to eight months [end deletion] [begin insertion] [end insertion] to facilitate installation of the shoring and decking.  One option would be to reroute the transit lines to Sutter, Mason, and Market Streets. [begin deletion]  Temporary disruption to BART service could occur during construction. [end deletion]

Construction of a TBM retrieval shaft near Washington Square Park for the North Beach Tunnel Construction Variant would require the temporary relocation of bus stops for the 30-Stockton and 45-Union/Stockton lines, along Columbus Avenue between Union and Powell Streets.  This construction approach would require the closure of one side of the street while the shaft is excavated, keeping one

travel lane in each direction, and then switching over to the other side of the street to complete the shaft.  This shift in traffic lanes may also require the temporary relocation of overhead wires on the 30-Stockton and 45-Union/Stockton to accommodate continued transit operations.  This construction activity is estimated to take six months, at which point the shaft would be covered and normal street operations would be restored.  If the North Beach Tunnel Construction Variant is not approved, the TBM extraction shaft would be at the Chinatown off-street station site and would last approximately one week.  Trucks and cranes would occupy the nearside curb parking lane to haul materials and load the TBM. 

Mitigation Measures

Mitigation measures would be same as those proposed under Alternative 2 [begin deletion] , except as described below.  The MTA would continue to coordinate with the TJPA and Golden Gate Bridge, Highway and Transportation District (GGBHTD) to minimize construction impacts on Golden Gate Transit bus operations.  MTA would stage excavation shaft construction and utility relocation to maintain access to the bus storage facility by Golden Gate buses and work with GGBHTD to develop bus detour routing plans to ensure continued access.  If access to the construction shaft is needed, it would be scheduled so as not to conflict with the periods when buses are entering or exiting the bus storage site. [end deletion]

[begin deletion] MTA and BART will prepare and enter into a Station Improvement Coordination Plan to include construction management procedures and processes to address any and all construction and operational impacts resulting from the tunnel boring.  MTA will also coordinate with BART to develop bus bridges, if needed, public outreach, and other programs to minimize impacts to transit riders during construction. [end deletion]

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Transit  impacts would be the same as those described under the Alternative 3A although the overall duration of construction would be shorter by one half year for the Fourth/Stockton Alignment Option B as tunnel construction would be completed more rapidly.  Unlike Alternative 3A, the bus stop located at the southwest corner of the Fourth and Howard Streets intersection would remain at its current location throughout the construction period as a result of the reduced length of the Moscone Station.  Also, Stockton Street, between Geary and Ellis Streets may need to be closed completely [begin deletion] for an estimated six to eight months [end deletion] for installation of the secant piles for the deep cut-and-cover platform section of the station.  To shorten the duration in which total closure of Stockton Street to traffic would be required, night time and weekend work would be undertaken.

Mitigation Measures

Mitigation measures would be same as those proposed under Alternative [begin insertion] 2 [end insertion] [begin deletion] 3A [end deletion] .

6.3.2 traffic

Alternative 2 – Enhanced EIS/EIR Alignment

This alternative would result in the greatest surface disruption during the construction period due to the nature of the SXM construction methods.  This alternative requires a longer and more extensive utility relocation process and the greater degree of construction activity at street level.

As discussed in Section 6.2, at most times when construction is underway south of Market Street, only two travel lanes would be operational next to the construction areas along Third and Fourth Streets.  With only two travel lanes, congested traffic conditions would occur during commute and non-commute periods.  Construction would affect surface street operations for up to 36 months.  To alleviate congestion

along Third and Fourth Streets during construction, the DPT identified potential detour routes (see Figures E-1 and E-2 in Appendix E).

During construction of the subway across Market Street, traffic operations along Market Street could be affected for up to six weeks, following the relocation of utilities.  During construction of the subway segment north of Market Street, a lane on Geary Street would be closed for three to six months.  For 12 to 18 months, there would be times when Stockton Street, from Geary Street to Sutter Street, would be reduced to one lane and short durations when complete closure may be required.  Potential detour routes during construction along these streets are illustrated in Figures E-3 and E-4 (see Appendix E). 

During construction of the Chinatown Station closure of one traffic lane, in addition to curb-side parking, would occur along Stockton Street to accommodate loading and unloading of heavy equipment for approximately one to three days at a time.

Removal of spoils and delivery of backfill for this Alternative would generate an estimated 8 truck trips per day during the 4.5 year construction period of the guideway plus an additional 8 to 10 truck trips during the two-year excavation period for each of the four stations.

Mitigation Measures

The construction-related traffic impacts could be alleviated or reduced with the following measures.

To alleviate some of the congestion that would result adjacent to construction of the subway, the DPT has identified potential traffic detours (refer to Figures E-1 through E-4 in Appendix E).  Prior to final design, the MTA would select the most appropriate detour routes [begin deletion] , working in cooperation with community and business organizations, [end deletion] and develop temporary transportation system management measures along these routes, e.g. additions of turn lanes at key intersections, conversion of parking lanes into peak period travel lanes, etc.  Detour routes would be advertised prior to construction in the appropriate media.  When detours are initially implemented, traffic control police would monitor critical locations along the detours to promote uncongested traffic flow.  All traffic detour measures would be implemented in coordination with other concurrent construction projects, e.g., Mission Bay Redevelopment.

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Traffic impacts would be the same as those described for Alternative 2, except as noted below.  Third, Harrison, Kearny, and Geary Streets would not be directly impacted.  Potential construction detour routes for the Fourth/Stockton Alignment Option A are shown in Appendix E, Figure E-5 through E-8.

Two lanes of traffic on Fourth Street, between Howard and Folsom Streets, would be closed for approximately four months during installation of the shoring at Moscone Station.  At Union Square/Market Street Station, Stockton Street would be reduced to two lanes between Post and Geary Streets and one lane between Geary and Ellis Streets.

In order to extract the TBM north of the Chinatown Station, an underground shaft would be constructed with a surface opening on Columbus Avenue between Union and Filbert Streets.  During the six-month construction period of the shaft and during the approximately one week required for extraction of the machine, the number of traffic lanes on this block of Columbus Avenue would be reduced to just one lane in each direction.  The traffic lanes would be shifted away from the construction area, depending on which side of Columbus Avenue is closed.  Overhead wires for the 30-Stockton, 41-Union, and 45-Union-Stockton trolley coach service may need to be shifted over one lane during this period to accommodate continued transit operation on these lines.  Figure E-8 illustrates the potential detour routes around the construction site.

This Alternative would generate an estimated 18 truck trips per day during the 2.5 year excavation of the guideway, 13 truck trips during the two-year excavation period for the Moscone Station, and 7 truck trips per day for the excavation of the Union Square/Market Street Station (3.0 year construction period) and the Chinatown Station (2.5 year construction period) associated with soils excavation and backfill.

Mitigation Measures

The construction-related mitigation measures would be the same as those described under Alternative 2, except as noted.  Muni could implement motor coach service for the 30-Stockton, 41-Union, and 45-Union/Stockton lines if the overhead wires need to be de-energized and removed for the duration of the shaft construction on Columbus Avenue.  To alleviate some of the congestion that would result adjacent to construction of the light rail line, the DPT has identified potential traffic detours (refer to Figures E-5 and E-8 in Appendix E).

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Traffic impacts would be the same as those described for Alternative 3A, except as noted below.  The overall duration of construction would be shorter by one half year.  Construction of the Chinatown Station may require the shifting of the traffic lanes on Stockton Street between Clay and Washington Streets away from the construction site and detouring traffic in the Chinatown area.  Potential construction detour routes for the Fourth/Stockton Alignment Option B are shown in Appendix E, Figures E-9 through E-12.

This alternative would generate an estimated 23 truck trips per day during the 2.0-year excavation period of the guideway, 25 daily truck trips during the 1.0-year excavation period for the Moscone Station, 20 truck trips per day for the 2.0-year excavation period of the Union Square/Market Street Station, and 9 truck trips per day for the 2.0-year excavation period for the Chinatown Station associated with soils excavation and backfill. 

Mitigation Measures

Mitigation measures would be the same as those described under Alternative 3A, except that traffic detour routes for this alternative are shown in Appendix E, Figures E-9 through E-12.

6.3.3 freight and loading

Alternative 2 – Enhanced EIS/EIR Alignment

As discussed previously, during construction of the Enhanced EIS/EIR Alignment, congested traffic conditions would result throughout the day along the roadways under construction.  Trucks using the affected streets would be subject to the same delays as passenger traffic. 

During construction of the Enhanced EIS/EIR Alignment, when portions of King, Third, Fourth, and Harrison Streets are under construction, parking would not be allowed on either side of the street in the construction zone.  This would prohibit the use of curb lanes for parking of trucks to load and unload goods.  Trucks would be required to park on nearby side streets, or two or more blocks away where no construction is underway.  Similar freight loading impacts would occur north of Market Street during construction along Kearny, Geary, and Stockton Streets.  Access to the Moscone Center loading area would be maintained during construction along Third Street between Clementina and Howard Streets.

[begin deletion] Construction of the Union Square/Market Street Station would impact loading and freight activities on Stockton Street between Sutter and Geary Streets.  Loading and freight would also be affected on Geary Street between Market/Kearny and Stockton Streets due to the guideway tunnel construction.  Curb parking would be eliminated along these streets during various stages of construction to accommodate traffic flow around the work area and trucks for equipment and materials delivery and spoils removal. [end deletion]

[begin deletion] Freight and loading activities near the Chinatown Station would be impacted, although the direct impacts would only be limited to the east side of Stockton Street between Clay and Sacramento Streets.  The demolition of the existing structures and construction of the new station headhouse [end deletion] [begin deletion] at this location would require curb space on the east side of Stockton Street to accommodate trucks for equipment and materials delivery and spoils removal. [end deletion]

Mitigation Measures

To alleviate some of the congestion that would result adjacent to construction of the light rail line, the DPT has identified potential traffic detours (refer to Figures E-1 and E-4 in Appendix E).

During construction of the Enhanced EIS/EIR Alignment, a portion of the curb parking lanes remaining open in the construction area, or just upstream or downstream of the construction area, may be converted to short-term loading zones to enable truck loading and unloading and delivery of goods to nearby businesses.  Temporary truck loading zones on the side streets may need to be established for the duration of the Project construction to offset any impacts along the streets that are directly affected by construction (Third, Fourth, Harrison, Kearny, Geary, and Stockton Streets).

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

As discussed previously, during construction of the Fourth/Stockton Alignment Option A (LPA), congested traffic conditions would result throughout the day along the roadways under construction.  Trucks using the affected streets would be subject to the same delays as passenger traffic. 

During construction of the Fourth/Stockton Alignment Option A (LPA), when portions of Fourth Street are under construction, parking would not be allowed on either side of the street in the construction zone.  This would prohibit the use of curb lanes for parking of trucks to load and unload goods.  Trucks would be required to park on nearby side streets, or two or more blocks away where no construction is underway.  Similar freight loading impacts would occur during construction along Stockton Street.

[begin deletion] Construction of the Union Square/Market Street Station would impact loading and freight activities on Stockton Street between Post and Market Streets and a portion of Ellis Street between Stockton and Powell Streets.  Curb parking would be eliminated along these streets during various stages of construction to accommodate traffic flow around the work area and trucks for equipment and materials delivery and spoils removal. [end deletion]

[begin deletion] Freight and loading activities near the Chinatown Station would be impacted, although the direct impacts would only be confined to the east side of Stockton Street between Clay and Sacramento Streets.  The demolition of the existing structures and construction of the new station head house at this location would require curb space on the east side of Stockton Street to accommodate trucks for equipment and materials delivery and spoils removal. [end deletion]

[begin deletion] If the North Beach Tunnel Construction Variant is adopted, construction of the extraction shaft on Columbus Avenue between Powell and Union Streets would have no effect on loading and freight activities as there are no loading zones on this block.  However, access to loading and freight zones on Union Street between Stockton and Powell Streets and on Columbus Avenue between Union and Stockton Streets may be impacted due to restrictions in traffic circulation and detours in the area for the duration of the shaft construction [end deletion] .

Mitigation Measures

Mitigation measures would be the same as those described above under Alternative [begin insertion] 2 [end insertion] [begin deletion] 3A, except [end deletion] [begin insertion] as noted below [end insertion] [begin deletion] Union Street [end deletion] [begin deletion] and Columbus Avenue would also be directly impacted by construction and would require converting a portion of curb parking upstream or downstream from construction site to loading and unloading zones for temporary access to businesses. [end deletion]   DPT will work with the property and business

owners on Perry and Stillman Streets to develop temporary detour routes for traffic to maintain access to their properties throughout the construction period.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Freight and loading impacts would be the same as described under Alternative 3A, except as noted below. The construction of the portal under the I-80 freeway would affect the access to Perry and Stillman Streets.  Temporary closure of the eastern most lane of Fourth Street between Bryant and Harrison Streets would be required for limited durations to complete the excavation for the portal.  Access to the businesses and residences along Perry and Stillman Streets would be maintained at all times during the construction, however, access to the two streets may be limited to Third Street for short periods when the closure of the eastern lane is required.

Cumulative construction impacts would be experienced by businesses and residences bordering the block bounded by Perry, Third, Stillman, and Fourth Streets as a result of three sequential construction projects in the vicinity.  The I-80 retrofit project is currently under construction, the construction of the Golden Gate Transit bus storage facility will follow, and the Central Subway Project construction is expected to begin in 2010.  While construction and muck removal for the Central Subway Project would be confined to Fourth Street, temporary short-term modifications to traffic circulation and access would likely be required on Perry and Stillman Streets.

[begin deletion] Construction of the Union Square/Market Street Station would impact loading and freight activities on Stockton Street between Geary and Ellis Streets and a portion of Ellis Street between Stockton and Powell Streets since the method of construction used would be cut-and-cover.  As described in Section 6.2.3, the installation of shoring for the platform section of the station may require Stockton Street to be shut down to traffic completely for a period of six to eight months.  In addition, the installation of shoring and decking would also require at least two traffic lanes on Stockton Street to be closed for about 10 to 12 months.  During these stretches of construction activity, there would be no access to the loading and freight zones on Stockton Street.  Ellis Street would experience similar impacts to loading and freight as it would be reduced to one traffic lane to accommodate the construction staging area. [end deletion]

[begin deletion] Freight and loading activities near the Chinatown Station would be impacted, although the direct impacts would only be confined to the southwest corner of Stockton and Washington Streets.  The demolition of the existing structures and construction of the new station head house at this corner would require curb space on the west side of Stockton Street and the south side of Washington Street to accommodate trucks.  [end deletion]

[begin deletion] If the North Beach Tunnel Construction Variant is adopted, construction of the extraction shaft on Columbus Avenue between Powell and Union Streets would have no effect on loading and freight activities as there are no loading zones on this block.  However, access to loading and freight zones on Union Street between Stockton and Powell Streets and on Columbus Avenue between Union and Stockton Streets may be impacted due to restrictions in traffic circulation and detours in the area for the duration of the shaft construction [end deletion] .

Mitigation Measures

Mitigation measures would be the same as those described above under Alternative [begin insertion] 2 [end insertion] [begin deletion] 3A [end deletion] , except as noted below.  DPT will work with the property and business owners on Perry and Stillman Streets to develop temporary detour routes for traffic to maintain access to their properties throughout the construction period.

6.3.4 parking

Alternative 2 – Enhanced EIS/EIR Alignment

As discussed in Section 6.2, all on-street parking would be prohibited in construction zones.  Therefore, substantial curb parking areas would be temporarily removed during construction, placing higher parking demands upstream and downstream of the construction zone, and on nearby streets. [begin deletion]   Parking spaces that would be permanently lost as a result of the Central Subway Project are discussed in Section 3.2.4, [end deletion]   Prior to final design, the [begin deletion] SF [end deletion] MTA would select the most appropriate detour routes [begin deletion] , working in cooperation with community and business organizations, [end deletion] and develop temporary transportation system management measures along these routes, e.g. additions of turn lanes at key intersections, conversion of parking lanes into peak period travel lanes, etc.   The SXM method of construction would require sequential movement of activities block by block along the Corridor.  With this sequence of utility diversions, jet grouting, and installation of soil cement walls for shoring of the guideway tunnels, parking on consecutive blocks would be temporarily eliminated throughout the duration of Project construction.

Mitigation Measures

During construction of the Enhanced EIS/EIR Alignment, signs denoting alternative parking areas (e.g., public parking garages) could be placed upstream of and through the construction zones.  To improve the accessibility to businesses in the Corridor, it is recommended that retained and added (where applicable) parking spaces be designated for short-term parking and loading, especially in commercial districts.  Near commercial establishments, parking turn-over should be encouraged through the use of time limits (e.g., parking meters, signed restrictions, etc.).  These improvements would be incorporated into the development of the project’s final plans.

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Parking impacts would be less than those described for Alternative 2 as there would be less surface disruption with this alternative.

Mitigation Measures

The mitigation measures would be the same as those described for Alternative 2.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Parking impacts would less than those described for Alternative 2 as there would be less surface disruption with this alternative.

Mitigation Measures

Mitigation measures would be the same as described for Alternative 2.

6.3.5 pedestrians

Alternative 2 – Enhanced EIS/EIR Alignment

During construction of the Enhanced EIS/EIR Alignment, the sidewalks on both sides of Third, Fourth, Harrison, Market, Kearny, and Geary Streets would remain open, except as noted below.  

The following temporary sidewalk closures would be required during construction of Alternative 2 (access to adjacent businesses would be maintained during business hours):

· East side of Third Street, between Folsom and Howard Streets and between Tehama Pedestrian Way and Clementina Street, for construction of Moscone Station;

· Each side of Third Street, between Mission and Market Streets, for construction of the Market Street Station;

· South side of Market Street, between Third and New Montgomery Streets, including Annie and Stevenson Streets for construction of the Market Street Station;

· Each side of Stockton Street, between Sutter and Geary Streets, for construction of the Union Square Station.

· The west sidewalk of Stockton Street, between Sacramento and Clay Streets, would be partially closed during construction of the Chinatown Station.

Pagoda Alley and Hang Ah Alley would remain open to pedestrian use during construction of the Chinatown Station.  During construction, all open sidewalks would be at least six feet wide and efforts would be undertaken to retain the full widths during construction.  Some pedestrian crossings of the above streets would need to be temporarily closed, but pedestrians would be re-routed through nearby crosswalks or assisted across the street by traffic control personnel.  This would increase walking distances for pedestrians during construction.

Mitigation Measures

During excavation of the subway stations, access to all abutting businesses would be maintained either through the existing or a reduced sidewalk area or via temporary access ways, e.g., ramps, planking, etc.  Signs would be installed indicated that the businesses are “open during construction.”  All temporary access ways would be in compliance with the ADA.  Temporary pedestrian walkways would be covered to protect pedestrians from noise, dust, and visual annoyances during construction.

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

The following sidewalk closures would be required during construction of Alternative 3 (access to adjacent businesses would be maintained during business hours):

· The west side of Fourth Street, temporarily between Howard and Clementina Streets and fully closed between Clementina and Folsom Streets for the construction of the Moscone Station;

· The northwest corner of Howard and Fourth Streets fully closed during construction of station entrances and partially closed during construction of the elevator shaft at Moscone Station.

· The west side of Stockton Street, fully closed between Post and Geary Streets for construction of the Union Square/Market Street Station;

· The east side of Stockton Street, temporarily closed between Post and Geary Streets for construction of the Union Square/Market Street Station;

· Each side of Stockton Street, between Geary and O’Farrell Streets, temporary partial closure (one side at a time) during construction of the Union Square/Market Street north platform cavern access shaft;

· Each side of Stockton Street, between Ellis and O’Farrell Streets, temporary closure (one side at a time) during construction of the Union Square/Market Street south platform cavern access shaft;

· Ellis Street, temporary partial closure on the south side, and fully closed on the north side adjacent to [begin deletion] One Stockton Street ( [end deletion] the Apple Store [begin deletion] ) [end deletion] , for the Union Square/Market Street Station;

Pagoda Alley and Hang Ah Alley and the sidewalks between Sacramento and Clay Streets, in front of the station access site, would remain open to pedestrian use during construction of the Chinatown Station.  Temporary closure of a section of sidewalk would be necessary for construction of the emergency exits on the west side of Stockton Street adjacent to Clay Street.  During construction, all open sidewalks would be at least six feet wide and efforts would be undertaken to retain the full widths during construction.  Some pedestrian crossings of the above streets would need to be temporarily closed, but pedestrians would be re-routed through nearby crosswalks or facilitated across the street by traffic control personnel.  This would increase walking distances for pedestrians during construction.

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

During construction of the Fourth/Stockton Alignment Option B (Modified LPA), the sidewalks on both sides of Fourth Street, and Stockton Street would remain open, except during installation of shoring for the Moscone and Union Square/Market Street subway stations, when only one sidewalk would be open on each side of the station area at a time. 

During construction, all open sidewalks would be at least six feet wide and efforts would be undertaken to retain the full widths, whenever possible, during construction.  Some pedestrian crossings of the above streets would need to be temporarily closed, but pedestrians would be re-routed through nearby crosswalks or facilitated across the street by traffic control personnel.  This would increase walking distances for pedestrians during construction.

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

6.3.6 Bicycles

Alternative 2 – Enhanced EIS/EIR Alignment

During construction of the Enhanced EIS/EIR Alignment, only two travel lanes would be operational next to the construction areas on along Third and Fourth Streets.  With only two travel lanes, congested traffic conditions would occur during commute and non-commute periods and bicycle travel in the shared lanes could be challenging.  Diversion of traffic onto Second and Fifth Streets may also impact bicycle travel on Bicycle Route #11 and Bicycle Route #19, respectively.  During construction along Geary and Stockton Streets, only one travel lane would be maintained at times, temporarily impacting bicycle travel, especially on Bicycle Route #17.

Mitigation Measures

To alleviate or reduce the anticipated impacts, it is recommended that during construction of the Enhanced EIS/EIR Alignment, every effort would be made to retain a wide curb or outside travel lane to facilitate bicycle travel.  Where this is not possible, signage should be erected indicating temporary alternative routes for bicyclists.  Existing bicycle traffic on Fourth Street could be diverted to Fifth Street.  If bicycle lanes are provided, as identified in the San Francisco Bicycle Program’s May 2005 Proposition K 5-Year Prioritization Program, this would further facilitate bicycle travel.  The same is true for existing bicycle traffic on Third Street diverting to Second Street.

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Construction impacts would be the same as those described under Alternative 2, during installation of shoring at Moscone Station.  At Union Square/Market Street Station travel lanes would be reduced to a single lane on Stockton Street, between Post and Ellis Streets.  Third, Harrison, Kearny and Geary Streets would not be disrupted by construction. 

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Construction impacts at Moscone Station would be the same as described under Alternative 3A.  During construction of the Union Square/Market Street, Stockton Street, between Geary and Ellis Streets would be reduced to a single lane and at times, may need to be closed entirely.

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

6.3.7 emergency VEHICLE access

Alternative 2 – Enhanced EIS/EIR Alignment

It is expected that the emergency access from Fire Station #8 on Bluxome Street and Fire Station #1 on Howard Street would be impacted by the construction along Third and Fourth Street, as discussed in Section 3.2.2.  Although two travel lanes would be operational next to the construction areas along Third and Fourth Streets, congested traffic conditions would occur during commute and non-commute periods.  Construction in the vicinity of the fire stations would affect surface street operations for 18 to 24 months. 

During construction of the North of Market segment, the number of traffic lanes on Geary Street, and then on Stockton Street, would be reduced (see Section 6.3.2).  Potential detour routes during construction along these streets are illustrated in Figures E-3 and E-4 (see Appendix E).  As with Fire Station #8 on Bluxome Street near Fourth Street, these detour routes for vehicular traffic could be used as alternative emergency access routes for Fire Station #1. 

Construction of the Chinatown Station on Stockton Street may require closure of one lane for loading and unloading of heavy equipment, in addition to curbside parking areas.  These temporary closures for the duration of the loading and unloading activities could take approximately one to three days.  This may affect the access and response times of emergency vehicles from Fire Station #2 (1340 Powell Street between Broadway and Pacific Avenue) if Stockton Street is used in an emergency response.

Mitigation Measures

MTA would require contractors to submit a site specific emergency access response plan as part of compliance with bid specifications.  The plan would include fire department and emergency services access to construction areas, maintainability of emergency services such as fire hydrants, and demobilization of plant and equipment impacting access to adjacent properties and buildings.  Potential detour routes have been identified, which could be used as alternative emergency access routes, in order to alleviate congestion along Third and Fourth Streets during construction (see Figures E-1 and E-2 in Appendix E).

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Emergency access impacts would be the same as described under Alternative 2, except as noted below.

Guideway tunnels would be constructed by TBMs so impacted emergency access is limited to parcels on the west side Fourth Street, between Clementina and Howard Streets, and to Moscone Center West, on the northwest corner of Howard and Fourth Streets.  During construction of the Union Square/Market Street Station, temporary lane closures would require emergency vehicles to use alternate routes.

If the Tunnel Boring Machine were extracted in North Beach rather than at the Chinatown station, there would be an approximately one less week during which access in Chinatown would be disrupted to extract the TBM.

Mitigation Measures

Mitigation measures would be the same as described under Alternative 2, except proposed construction detour routes are shown in Appendix E, Figures E-5 through E-8.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Emergency access impacts would be the same as described under Alternative 3A, except there would be no impacts to the Moscone Center West on Fourth and Howard Streets for the Moscone Station; no impacts on Stockton Street, between Post Street and Maiden Lane at the Union Square/Market Street Station; and access to property on the west side of Stockton Street, between Jackson and Washington Streets, would be restricted during construction of the Chinatown Station exit.

Mitigation Measures

Mitigation measures would be the same as described under Alternative 2, except proposed construction detour routes are shown in Appendix E, Figures E-9 through E-12.

6.4 construction impacts and mitigation for land use

6.4.1 land use

Alternative 2 - Enhanced EIS/EIR Alignment

Construction of the Enhanced EIS/EIR Alignment would not cause substantial changes in land use or neighborhood character.  Temporary construction impacts associated with parking and access to land uses in the Study Area are addressed in Section 6.3, Transportation.

Mitigation Measures

Public information programs, including signage, as well as steps to ensure uninterrupted access to all uses along the Corridor, shall be used to minimize the construction impacts on neighboring land uses. 

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction of the Fourth/Stockton Alignment Option A would not cause any substantial changes in land use, disrupt neighborhood character, or physically divide an existing neighborhood.  Parking spaces in the Corridor in the vicinity of the portal and stations, and along the surface segment would be temporarily lost during the construction period.  Vehicular and pedestrian access and freight deliveries to buildings in the vicinity of the tunnel portal and stations may be affected during the construction period, but this impact would generally be temporary during the construction period and would not substantially alter the use of properties adjacent to construction activities.  (See Chapter 3.0 and Section 6.3, Transportation, for a detailed discussion of parking and access issues that affect land use.)

Mitigation Measures

Mitigation measures would be the same as identified for Alternative 2.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Land use impacts associated with the Fourth/Stockton Alignment Option B would be the same as those described for Fourth/Stockton Alignment Option A except as noted here.  The main difference would be a greater area of parking and traffic disruption along Fourth Street due to the longer segment of at-grade railway and construction of a surface station at Fourth and Brannan Streets that would require the use of more street space and require longer periods of surface disruption.  These impacts are discussed in Section 6.3.

[begin deletion] An amendment of the Planning Code, which prohibits the demolition of residential apartment units in the Chinatown Residential Neighborhood Commercial District, would be required for the Chinatown Station.  The impacts would be the same as those discussed in Section 6.5.2, Property Acquisition. [end deletion]

Mitigation Measures

Mitigation measures would be the same as identified for Alternative 2.

6.5 construction impacts and mitigation for socioeconomics

6.5.1 socioeconomics

Alternative 2 - Enhanced EIS/EIR Alignment

Design and construction of the Enhanced EIS/EIR Alignment would cost an estimated $229 million for professional services and labor and the expenditure of approximately $1,095 million for materials/facilities (refer to Table 5-1).  This would provide temporary employment opportunities for the City and/or region and would be considered a beneficial impact.

Mitigation Measures

No substantial adverse impacts on demographic or economic conditions are anticipated from the construction of the Enhanced EIS/EIR Alignment.  While beneficial to the City and region in terms of employment opportunities and income, short-term employment impacts are not considered to be substantial.  No mitigation measures would be required.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Design and construction of Fourth/Stockton Alignment Option A would cost an estimated $202 million for professional services and labor and the expenditure of approximately $908 million for materials/facilities (refer to Table 5-1).  As described above for the Enhanced EIS/EIR Alignment, this would be a beneficial impact.

Mitigation Measures

No mitigation measures would be required.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Design and construction of the Central Subway Fourth/Stockton Alignment Option B would cost an estimated $188 million for professional services and labor and the expenditure of approximately $1,026 million for materials/facilities (refer to Table 5-1).  As described above for the Enhanced EIS/EIR Alternative, this would be a beneficial impact.

Mitigation Measures

No mitigation measures would be required.

6.5.1 acquisition and displacement

This section addresses potential impacts related to the acquisition and relocation of businesses or residents as a result of the Project.  The federal Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970 (Public Law 91-646) and the State of California Relocation Act (Chapter 16, Section 7260 et seq. of the Government Code) contain specific requirements that govern the manner in which a government entity can acquire property for public use.  The public entity is required to establish the fair market value of the property before acquisition.  Adherence to the state and federal laws is designed to ensure just compensation for all acquired properties, and to minimize adverse impacts on the affected property owners.

The same federal and state laws that govern acquisition also govern relocation.  Under these laws MTA would be required to develop a detailed relocation plan designed to minimize impacts on the businesses to be displaced by the Project.  The plan would assess the relocation needs of all potential displacees and develop a program that would provide relocation assistance and payments.  Minimum relocation payments are set by law, and include moving expenses and search expense payments for businesses.  Relocation assistance programs include, at a minimum, referrals to comparable locations for displacees.  For displaced on-site service delivery space or dedicated parking, suitable replacement spaces would be identified or a determination made of the viability of the displacee's business without the displaced vehicle access.

The California Code of Civil Procedure (Sections 1230 to 1273) outlines regulations and guidelines governing the exercise of the power of eminent domain to acquire property for a public use.  The owner of property acquired by eminent domain is entitled to just compensation for that property.  If the power of eminent domain is necessary to acquire property for this Project, all applicable procedures outlined in the civil code will be followed.

For the purpose of this analysis, properties that would need to be acquired for the construction and operation of an alternative are identified.  Field surveys were conducted to identify potential acquisitions and displacements, as well as to estimate current employment at potentially affected businesses, based on the type and size of the potentially affected business.  Acquisition and displacement impacts are considered significant if an alternative would 1) displace a substantial number of residents; 2) result in the loss of housing units affordable to people with low or moderate incomes; 3) displace businesses unable to relocate to economically viable areas; 4) result in a substantial loss of business clientele; or 5) result in the loss of a substantial number of jobs.

Table 6-2 lists the acquisitions that would be necessary to implement the alternatives.  The information contained in this table is discussed in the section below.

TABLE 6-2

ACQUISITION AND RELOCATION REQUIREMENTS

Source:  PB/Wong, 2007
Alternative 2 - Enhanced EIS/EIR Alignment

Construction of the Enhanced EIS/EIR Alignment would require securing easements for the Moscone and Market Street Stations and a long-term encroachment permit for the Union Square Station.  The entrance to the Moscone Station would be located along a pedestrian corridor (Tehama Street) on the east side of Third Street between Howard and Clementina Streets.  Easements would be required at 255 Third Street for the vent shafts at the southeast exterior of the garage, as well as, the installation of two elevators under the canopy entrance at the northwest corner of the garage.  This would displace an entrance to the western-most retail bay, but would not require elimination of any parking spaces.  At the Market Street Station, the vent shafts would require an easement under Stevenson Street between Third and Annie Streets and the elimination of 30 spaces in the Hearst garage.  The Union Square Station entrance and vent shafts would eliminate 29 parking spaces at the Union Square garage.   The MTA, which has authority over the Union Square Garage, would need to amend the management and operator agreements for the garage to address the reduction in parking.  Union Square is a public park under the jurisdiction of the San Francisco Recreation and Park Department.  [begin deletion] Compensation for the loss of parking spaces would be required in accord with the Uniform Relocation Act.  [end deletion] Use of a portion of this Park would require a long-term encroachment permit and a Section 4(f) approval (see Section 10.0).  

Two additional easements would be needed for the subway alignment under buildings at 425 Fourth Street (southeast corner at Harrison) and 370 Third Street (northwest corner at Harrison).  Neither easement would affect the use of the buildings.  There would be one acquisition in fee of a parcel at 814-848 Stockton Street, between Sacramento and Clay Streets, for the Chinatown Station entrance and vent shafts.  This displacement would require the relocation of five small businesses along Stockton Street and five small businesses along Hang Ah Alley with an estimated fewer than 10 employees each [begin insertion] and one to two residential units in the second floor of the building [end insertion] .  As stated in Section 4.2.4, the population in the Chinatown area is predominantly Asian and has a high percentage of low income residents; therefore the residential displacement would likely displace affordable housing units, resulting in an adverse impact.

Utility relocation in sidewalks may require access to or use of existing basements located beneath the sidewalks, particularly in the Union Square area and along Market Street for the pedestrian concourse between Third Street and the Montgomery Station.  Property owners with sub-sidewalk basements may be required to vacate this space to make room for relocated utilities.  Temporary access to buildings that are identified as susceptible to settlement along the alignment may be required to perform inspections.  If settlement of a building is observed during construction, compensation grouting would be injected into the ground beneath these buildings from the street right-of-way.

MTA would follow the provisions of the Uniform Relocation Act and, where applicable, eminent domain law.  For the limited amount of acquisition that would occur for any Project alternative, Muni would act in accordance with existing federal and state relocation and acquisition laws to minimize the impact on affected property and business owners and on residents.

Mitigation Measures

No mitigation measures would be required beyond compliance with the Uniform Relocation Act and eminent domain law; however, development of affordable housing units on the Chinatown Station site above the station and ground floor retail where it is compatible with station access could further reduce the adverse impacts of displacement of existing [begin insertion] residential units and [end insertion] small businesses in Chinatown.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction of Fourth/Stockton Alignment Option A would require use of the Union Square plaza and garage to accommodate station entries and vent shafts resulting in removal of 29 parking spaces in the Union Square garage.  MTA would need to authorize the garage use and amend the management and operator agreements to address the reduction in parking, the Recreation and Park Department would need to approve a long-term encroachment permit for the use of the Union Square plaza, and Section 4(f) approval would be required (see Chapter 10.0).  [begin deletion] Compensation for the loss of parking spaces would be required in accord with the Uniform Relocation Act.  [end deletion] Three additional easements would be needed for the subway alignment under private buildings at 2 Stockton Street, 790-798 Market Street, and 44 Stockton Street.  None of these easements would affect the use of the buildings.  An existing agreement with BART for use of the joint entries at the Powell Street Station would need to be amended to provide additional access to the Union Square/Market Street Station. 

Construction of the Fourth/Stockton Alignment Option A would require two acquisitions in fee.  The first acquisition would be a parcel with a gas station at the northwest corner of Fourth and Folsom Streets (266 Fourth Street), required for the Moscone Station main entrance and vent shafts.  The second would be a parcel at 814-828 Stockton Street, between Sacramento and Clay Streets, required for the Chinatown Station entry and vent shafts.  The Stockton Street parcel acquisition would require the relocation of 10 small Chinatown businesses [begin insertion] and one to two residential uses above the businesses.  The residential displacement would likely displace affordable housing units and would result in adverse impacts to low income residents. [end insertion]

Utility relocation in sidewalks may require access to or use of existing basements located beneath the sidewalks, particularly in the Union Square area.  Property owners with sub-sidewalk basements may be required to vacate this space to make room for relocated utilities.  Temporary access to buildings along

the alignment that are identified as susceptible to settlement may be required to perform inspections.  If

settlement of a building is observed during construction, compensation grouting would be injected into the ground beneath these buildings from the street right-of-way.

The North Beach Tunnel Construction Variant would require an easement under a parcel at 1455 Stockton Street to accommodate the tunnel alignment. 

[begin insertion] Muni [end insertion] [begin deletion] MTA [end deletion] would follow the provisions of the Uniform Relocation Act and, where applicable, eminent domain laws.  MTA would act in accordance with existing federal and state relocation and acquisition laws to minimize the impact on affected property and business owners and residents. 

Mitigation Measures

No mitigation measures would be required beyond compliance with the Uniform Relocation Act and eminent domain law; however, redevelopment of affordable housing units on the Chinatown Station site above the station and ground floor retail where it is compatible with station access could further reduce the adverse impacts of displacement of existing residential units and small businesses in Chinatown.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option B (Modified LPA)

Construction of Central Subway Fourth/Stockton Alignment Option B would require use of Union Square plaza and Union Square Garage for station entries and vents resulting in removal of 34 parking spaces and use of the Ellis/O’Farrell Garage resulting in the removal of 24 parking spaces.  As with Option 3A, this would require MTA to amend the parking management and operator agreements in both the Union Square and Ellis/O’Farrell garages.  [begin deletion] Compensation for the loss of parking spaces would be required in accord with the Uniform Relocation Act.  [end deletion] The Department of Recreation and Parks would need to authorize [begin insertion] a long-term encroachment permit for the [end insertion] use of Union Square plaza [begin insertion] and a Section 4(f) approval would also be required [end insertion] .  Additional easements would be needed for the subway alignment under private buildings at 790-798 Market Street and at 2 Stockton Street.  These easements would not affect the use of these buildings.  An agreement for use of the BART entries on Market Street would need to be negotiated to provide additional access to the Union Square/Market Street Station.  [begin deletion] The BART entry (escalator and stairs) at One Stockton Street (in the Apple Store) at Ellis Street would need to be closed temporarily during construction and may need to be expanded to meet BART’s request. [end deletion]   There would be two acquisitions in fee.  The first acquisition would be a parcel occupied by a gas station at 266 Fourth Street, required for the Moscone Station entry and vent shafts.  The second would be a parcel at 933-949 Stockton Street, between Washington and Jackson Streets, required for the Chinatown Station entry and vent shafts.  These displacements would require the relocation of eight businesses (seven at the Chinatown property) plus 17 residential units located above the Chinatown businesses.  The Chinatown area is predominantly Asian

and has a high percentage of low income residents; therefore the residential displacement of 17 housing units would have adverse impacts. [begin deletion]   An amendment to the San Francisco Planning Code would be required for the demolition of the residential apartment units at this station site and the mitigation measures would be the same as those proposed for acquisition of the parcels. [end deletion]

Utility relocation in sidewalks may require access to or use of existing basements located beneath the sidewalks, particularly in the Union Square area.  Property owners with sub-sidewalk basements may be required to vacate this space to make room for relocated utilities.  Temporary access to buildings along the alignment that are identified as susceptible to settlement may be required to perform inspections.  If settlement of a building is observed during construction, compensation grouting would be injected into the ground beneath these buildings from the street right-of-way.

The North Beach Tunnel Construction Variant would require an easement under a parcel at 1455 Stockton Street to accommodate the tunnel alignment. 

MTA would follow the provisions of the Uniform Relocation Act and, where applicable, eminent domain law.  MTA would act in accordance with existing federal and state relocation and acquisition laws to minimize the impact on affected property owners, businesses, and residents. 

Mitigation Measures

No mitigation measures would be required beyond compliance with the Uniform Relocation Act and eminent domain law; however, redevelopment of affordable housing units on the Chinatown Station site above the station and ground floor retail could further reduce the adverse impacts of displacement of existing residential units and small businesses in Chinatown.  [begin deletion] MTA will provide rental or property leasing assistance to impacted businesses in addition to the relocation costs. [end deletion]

6.5.2 environmental justice findings

All Build Alternatives

Construction staging areas would be located at tunnel portals and station locations along the Central Subway Corridor.   Construction impacts, including traffic disruption, loss of on-street parking, noise, and dust would occur along the entire alignment, primarily in the areas around the tunnel portals and stations.  These temporary impacts would not disproportionably impact low-income populations or neighborhoods.

6.6 construction impacts and mitigation for community facilities and services

6.6.1 public and community facilities

Alternative 2 - Enhanced EIS/EIR Alignment

Construction of the Enhanced EIS/EIR Alignment would temporarily affect vehicular access and on-street parking for the public facilities along Third Street during construction of the tunnels, portal, and the Moscone and Market Street Stations.  Construction of the Union Square Station would temporarily affect pedestrian access along the eastern edge of Union Square plaza as this sidewalk (west side of Stockton Street) would be closed off during construction.  There is the potential for construction-related noise and dust impacts for the Chinatown station on the Willie “Woo Woo” Wong Playground, which is located behind the building that would be removed to accommodate the Chinatown Station on Stockton Street.  These impacts will lessen after the existing building is demolished and the excavated construction shaft is decked over at the station entrance site.  In addition, there would also be temporary impacts to the vehicular access to community facilities (including the Post Office on the west side of Stockton Street) along Stockton Street near the Chinatown Station entrance.  During various stages of the station construction, it is likely that portions of the street would have restricted vehicular access and the west sidewalk of Stockton Street would be closed during the station construction.  Construction activities also would temporarily increase noise and dust in these areas.

Mitigation Measures

In the vicinity of each station and along Third and Fourth Streets, alternative vehicular and pedestrian circulation patterns that permit continued access to community and public facilities in these locations during construction would be developed and clearly identified during final design, in consultation with Department of Parking and Traffic (DPT) staff.  Conditions of approval would be part of the permit process for construction of the Union Square Station, which would require a portion of the plaza and underground parking.  The facilities and access to the plaza would remain open for public use.  Noise limits will be included in the construction specifications to ensure that the construction is in compliance with City regulations.  A temporary noise wall would be constructed east of the construction site in Chinatown to minimize impacts to the adjacent alley and Willie “Woo Woo” Wong Playground from construction noise and dust.  Public access to the playground would not be affected.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction impacts for the Central Subway Fourth/Stockton Alignment Option A would be less than those identified for Alternative 2 as Third, Harrison, Kearny, and Geary Streets, east of Stockton Street, would not be disrupted.

Mitigation Measures

The mitigation measures would be the same as described above for Alternative 2.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Construction of Fourth/Stockton Alignment Option B would be the same as those discussed above for Alternative 3A, however, no impacts to Willie “Woo Woo” Wong Playground would occur with this alternative.  Rather, temporary construction-related noise and dust impacts would occur at the Gordon Lau Elementary School (located immediately west of the 933-949 Stockton Street Chinatown station site) during construction.  Vehicular access and on-street parking for the public facilities along Fourth Street in the Moscone Center/Yerba Buena Gardens area would be disrupted during construction of the Moscone Station.  Construction of the entrance to the Union Square/Market Street Station would temporarily affect pedestrian use and access along the eastern edge and southeastern corner of Union Square plaza, as this sidewalk would be closed off during construction.  There would also be temporary impacts to the vehicular access to community facilities located across the street from the proposed station entrance for the Chinatown Station along Stockton Street.  During various stages of the station construction, portions of the street would have restricted vehicular access, as described in Section 6.3, Transportation.  

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2 and 3A, however, a temporary noise wall would not be required at Willie “Woo Woo” Wong Playground.

6.6.2 police, fire, and emergency services

Alternative 2 - Enhanced EIS/EIR Alignment

Staging areas are often subject to vandalism and crime.  The proposed general staging areas for the Enhanced EIS/EIR Alignment would be located on the west side of Fourth Street north of Bryant Street.  This site would be used for the duration of the Project construction effort.  Secondary staging areas would be located near subway station sites:  Clementina and Kaplan Streets at Moscone Station, Stevenson and Annie Streets at Market Street Station, the west side of Stockton at Union Square Station, and the off-street site at the Chinatown Station.  Staging areas would be fenced and secured by Muni contractors and would not affect existing police services.  Emergency access and circulation would be maintained on streets leading to construction sites.  Reduction in traffic lanes or detours along Third, Fourth, Harrison, Kearny, Geary, and Stockton Streets could temporarily impact emergency service response times during construction.  (Refer to Section 6.3.7 for a more detailed discussion of construction impacts on emergency services.)

Mitigation Measures

During construction of above grade segments and stations it may be desirable to have a uniformed traffic control officer, paid for by Muni, at construction sites to facilitate traffic flow during peak use periods,  This would not impact police services throughout the City.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option A(LPA)

Construction impacts would be the same as  described above for Alternative 2, except that lane closures during construction would not occur on King, Third, Harrison, Kearny, or Geary Streets.

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Construction impacts would be the same as described above for Alternatives 2 and 3A, except the off-street site at the Chinatown Station would be located at 933-949 Stockton Street. 

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2 and 3A.

6.6.3 parks and recreation facilities

Alternative 2 - Enhanced EIS/EIR Alignment

Cut-and-cover station construction and guideway, tunnel construction using the special excavation method (SXM) along Third Street would temporarily affect traffic and pedestrian circulation at Yerba Buena Gardens.  Because the public plaza is set back from the street and because much of the excavation work would occur underground, construction noise, vibration, and dust would be limited to installation of shoring and would not be expected to affect the use of this area.  Union Square is located adjacent to the proposed excavation for the Union Square Station.  The sidewalk on the eastern edge of the plaza (on Stockton Street between Post and Geary Streets) would be closed for station construction and would serve as the principal work shaft site for the station.  In addition, the middle stairs along the eastern edge of the Union Square plaza would be closed to construct the station entries and vent shafts.  Noise, dust, and vibration would temporarily affect the use of the eastern portion of the plaza.  (See also Chapter 10.0, Section 4(f) Report.)  Construction at the Chinatown Station would not affect access to Pagoda Alley, Hang Ah Alley or to the Willy “Woo Woo” Wong Playground located to the east of the off-street station site.  Access to the construction site would be provided via Stockton Street.    Noise, dust, and vibration would be minimized through provision of a noise buffer wall between the Playground and the construction site. 

Mitigation Measures

For construction-related impacts to parks, recreational, or other public facilities, noise and vibration would be controlled by use of temporary construction walls along sidewalks and by muffling construction equipment.  Excessive idling of construction equipment would be controlled as a way of minimizing temporary increases in emissions.  In addition, construction activities will adhere to the guidelines provided in the San Francisco Noise Ordinance.  To control dust and particulate matter, construction crews would spray water or use dust palliatives in construction areas and cover dump truck loads with canvas or tarps.  Access to parklands and public facilities would be maintained during construction.  Construction activities (above-ground) at the Union Square Station would be scheduled to minimize disruption to the plaza during peak holiday periods.  A temporary noise wall would be constructed east of the construction site in Chinatown to minimize impacts to the adjacent alley and Willie “Woo Woo” Wong Playground from construction noise and dust.  Public access to the playground would not be affected.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction impacts due to cut-and-cover station construction on Fourth and Stockton Streets would be the same as described along Third Street for Alternative 2 above.  However, the use of the TBM methods for guideway tunnel construction would result in substantially less impact to the surface than is required for the near surface excavation method.

The North Beach Tunnel Construction Variant would require the excavation of the tunnel shaft within Columbus Avenue adjacent to the western edge of Washington Square Park.  No work would occur within the park, although there would be temporary affects to park users due to noise, dust, and vibration. 

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option B (Modified LPA)

The construction impacts would be the same as those described above for Alternatives 3A, except there would be no impacts to Willie “Woo Woo” Wong Playground. There would be temporary noise, vibration, and dust impacts during construction at the school playground at Gordon Lau Elementary School.

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2; however, a temporary noise wall would not be required at Willie “Woo Woo” Wong Playground.

6.7 construction impacts and mitigation for cultural resources

6.7.1 prehistoric and historical archaeological resources

Alternative 2 – Central Subway Enhanced EIS/EIR Alignment

Prehistoric Archaeological Resources.  The prehistoric CA-SFR-2 may be impacted as a result of construction trenching in two of the Alternative 2 sections: on Third Street, between Folsom and Harrison Streets; and on Third Street, between Harrison and Bryant Streets. Based on the range and quantity of cultural materials that are documented from CA-SFR-2, and the presence of human remains, the site appears potentially eligible for inclusion on the NRHP/ CRHR under Criterion D/4.  It is not certain that deposits associated with CA-SFR-2 extend into the project’s vertical Area of Potential Effect (APE).  (Refer to Figure 5-14, Geology.)

As a result of the geoarchaeological analysis summarized in Section 4.4 of this SEIS/SEIR and described in detail in the Historic Context Archaeological Survey Report (HCASR) (ASC 2007), at least 14 locations have been identified as sensitive for the presence of prehistoric archaeological resources along the Alternative 2 alignment. These locations, from south to north, are as follows:

· Construction Reaches 6 and 5, south of Market Street between King and Folsom Streets along Third Street, have two locations that are highly sensitive;

· Moscone Station is highly sensitive;

· Reach 4, between Howard and Mission Streets along Third Street, has two locations that are highly sensitive;

· Market Street Station has varying sensitivity (two highly sensitive locations and one of low sensitivity) depending on depth;

· Reach 3, between Mission Street and Geary/Stockton Street, has two locations that are highly sensitive;

· Union Street Station has varying sensitivity (one moderately sensitive area and one highly sensitive area) depending on depth;

· Reach 2, between Post and Clay Streets along Stockton Street,  has one highly sensitive location;

· Chinatown Station has one location of varying sensitivity (one moderately and one highly sensitive area), depending on depth;

· Reach 1, between Washington Street and Columbus Avenue and Union Street, has one location of high sensitivity.

No specific evidence confirms that subsurface prehistoric cultural deposits are present at these locations; the sensitivity assessments are based on preliminary geoarchaeological research.

Historical Archaeological Resources.  Construction of Alternative 2 would not affect known historical archaeological resources.  The block-by-block historic overview, developed in the HCASR to predict areas of potential historical archaeological sensitivity, identified six locations at which previously unrecorded archaeological resources might be encountered.  The locations, from south to north, are as follows:

· The Third Street Portal is moderately sensitive for the presence of early historic refuse deposits in fill (1840s-1850s);

· Market Street Station is highly sensitive for the presence of archaeological features and/or sheet refuse (1840s-1850s);

· Union Square Station is moderately sensitive for early historic refuse deposits in fill (1840s-1850s);

· Chinatown Station headhouse is highly sensitive for buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906);

· Two locations of Chinatown Station emergency stairs are highly sensitive for buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906).

Among the specific resources indicated by the block-by-block overview are:  potential caches of artifacts, as well as isolated objects within the Gold Rush era fill layer at the northbound portal on Third Street; historic tent pads and artifacts at the Market Street Station that may have been buried during filling of the Third Street roadway prior to 1854; and artifact caches dating prior to 1854 where the roadway was filled to grade at Union Square Station. At Chinatown Station, potential finds are artifact-filled features dating to the Gold Rush era or earlier, prior to street paving at the Chinatown Station Emergency Stairs; and architectural remains and archaeological features, dating up to and including 1906, beneath the modern sidewalks (based on an 1850s photograph), including basement room or niche extensions and tunnels of the type reported in San Francisco’s Chinatown and found elsewhere in California. Also possible are garden features, as well as artifact caches and architectural deposits, from the Gold Rush or earlier up to 1906, at the Chinatown Station headhouse location.

Mitigation Measures

The Central Subway Project is subject to Section 106 of the National Historic Preservation Act of 1966, as amended, and its implementing regulations at 36 CFR 800.  These regulations are carried out through a detailed set of procedures—known as the Section 106 Process—for the assessment and treatment of Project impacts on important resources.  As part of Section 106 Process compliance for the Third Street Light Rail Project; Muni, FTA, SHPO, and the Advisory Council on Historic Preservation signed a Programmatic Agreement (PA) in 1999.  The PA identified the steps to be taken to mitigate potential adverse effects of the Project on important archaeological resources (Appendix C).

FTA has initiated Section 106 consultation with the State Historic Preservation Officer concerning the Phase 2 Central Subway Project.  This process will lead to the negotiation of a new PA that will specify in detail how important archaeological resources within the current APE shall be treated.  Mitigation measures that are included in the present document will likely be complemented by additional treatments required by the PA.

Specific strategies for the treatment of legally important archaeological resources are presented in the Secretary of the Interior’s “Standards and Guidelines for Archaeological Documentation” (48 FR 44734-44737).  Mitigation programs for addressing potential impacts would be prepared within that context, based on specific finds, circumstances, and the resources’ potential eligibility to the NRHP and CRHR.

Two principal strategies for the mitigation of adverse Project effects on important resources are available: avoidance or data recovery through archaeological excavation.  Avoidance of resources would be difficult, if not impossible, due to engineering constraints, and it is prudent to assume that data recovery will be the measure required by the PA.  Specific field methodologies will be developed for specific resources within the context of a Research Design and Treatment Plan; the PA will require this document.  All archaeological work on NRHP- and CRHR-eligible and potentially eligible properties shall be conducted in accordance with “Treatment of Archaeological Properties: A Handbook” (ACHP 1990) and “Archaeology and Historic Preservation: the Secretary of the Interior’s Standards and Guidelines” (48 FR 44716-44742). Investigations shall be performed under the supervision of professionals whose education and experience meet or exceed the Secretary of the Interior’s “Professional Qualifications Standards” (48 FR 44738-44739).

The Project Sponsor (MTA) shall, in consultation with a qualified archaeologist, ensure that all State and federal laws and regulations regarding Native American concerns are strictly enforced.  Prior to construction, the Project Sponsor or representative shall initiate consultation with a representative of the Native American group having traditional authority over the Study Area; the goal of this consultation will be to come to agreement on protocols to be followed if prehistoric resources are discovered.  A consultant from this Native American group shall be solicited and, if possible, engaged to monitor all prehistoric archaeological testing and excavation.  If human remains are encountered during either construction or archaeological excavation, State Health and Safety Code Section 7050.5 shall be applied.  This regulation states that no further disturbance shall occur until the County Coroner has made the necessary findings as to origin and disposition pursuant to Public Resources Code 5097.88.

Despite high potential for archaeological resources within the project APE, it is not certain that resources will be affected or where this may occur.  Engineering and other logistical concerns constrain most forms of pre-construction archaeological testing.  However, limited subsurface testing using a push sampling device—such as a Geoprobe sampler—may be feasible for determining whether archaeological deposits are present within the horizontal and vertical APE in certain especially sensitive locations identified in the Project HCASR.  A field program of geoarchaeological exploration, conducted in conjunction with Project-related geotechnical investigations as described in the Project HCASR, may help refine subsurface sensitivity assessments and rule out unproductive geologic units.  The feasibility and scope of this program shall be determined through consultation between the MTA, the Environmental Review Officer of the City and County of San Francisco, and the consulting archaeologist.  The program may be conducted once a preferred alignment has been identified.  The goal of the study shall be to determine the presence or absence of prehistoric cultural deposits, site boundaries (within the APE) and potential for project impacts to resources; if the presence of archaeological deposits is substantiated, the program may be expanded to determine depositional integrity, cultural complexity, and potential NRHP/CRHR eligibility.

During construction, archaeological monitoring is warranted within those sections identified as moderately to highly sensitive for prehistoric and historical archaeological deposits, as identified in the HCASR and through pre-construction exploration, and as determined through consultation with the consulting archaeologist.  Identified resources shall be evaluated and treated in accordance with the requirements of the PA.

In addition to mitigation specified in the PA, measures listed below consist of Standard Archaeological Mitigation Measure III adopted by the City and County of San Francisco’s Major Environmental Analysis Section, some of which are similar to those previously described.

Based on a reasonable presumption that archeological resources may be present within the Project site, the following measures shall be undertaken to avoid any potentially significant adverse effect from the proposed Project on buried or submerged historical resources.  The Project Sponsor shall retain the services of a qualified archeological consultant having expertise in California prehistoric and urban historical archeology.  The archeological consultant shall undertake an archeological testing program as specified herein.  In addition, the consultant shall be available to conduct an archeological monitoring and/or data recovery program if required pursuant to this measure.  The archeological consultant’s work shall be conducted in accordance with this measure at the direction of the Environmental Review Officer (ERO).  All plans and reports prepared by the consultant as specified herein shall be submitted first and directly to the ERO for review and comment, and shall be considered draft reports subject to revision until final approval by the ERO.   Archeological monitoring and/or data recovery programs required by this measure could suspend construction of the Project for up to a maximum of four weeks.  At the direction of the ERO, the suspension of construction can be extended beyond four weeks only if such a suspension is the only feasible means to reduce to a less-than-significant level potential effects on a significant archeological resource as defined in CEQA Guidelines Sect. 15064.5 (a)(c).

Archeological Testing Program. The archeological consultant shall prepare and submit to the ERO for review and approval an archeological testing plan (ATP).  The archeological testing program shall be conducted in accordance with the approved ATP. The ATP shall identify the property types of the expected archeological resource(s) that potentially could be adversely affected by the proposed Project, the testing method to be used, and the locations recommended for testing.  The purpose of the archeological testing program will be to determine to the extent possible the presence or absence of archeological resources and to identify and to evaluate whether any archeological resource encountered on the site constitutes an historical resource under CEQA.

At the completion of the archeological testing program, the archeological consultant shall submit a written report of the findings to the ERO.  If based on the archeological testing program the archeological consultant finds that significant archeological resources may be present, the ERO in consultation with the archeological consultant shall determine if additional measures are warranted.  Additional measures that may be undertaken include additional archeological testing, archeological monitoring, and/or an archeological data recovery program. If the ERO determines that a significant archeological resource is present and that the resource could be adversely affected by the proposed Project, at the discretion of the Project Sponsor either:

· The proposed Project shall be re-designed so as to avoid any adverse effect on the significant archeological resource; or

· A data recovery program shall be implemented, unless the ERO determines that the archeological resource is of greater interpretive than research significance and that interpretive use of the resource is feasible.

Archeological Monitoring Program.  If the ERO in consultation with the archeological consultant determines that an archeological monitoring program shall be implemented the archeological monitoring program shall minimally include the following provisions:

· The archeological consultant, Project Sponsor, and ERO shall meet and consult on the scope of the AMP reasonably prior to any Project-related soils disturbing activities commencing. The ERO in consultation with the archeological consultant shall determine what Project activities shall be archeologically monitored.  In most cases, any soils-disturbing activities, such as demolition, foundation removal, excavation, grading, utilities installation, foundation work, driving of piles (foundation, shoring, etc.), site remediation, etc., shall require archeological monitoring because of the risk these activities pose to potential archaeological resources and to their depositional context;

· The archeological consultant shall advise all Project contractors to be on the alert for evidence of the presence of the expected resource(s), of how to identify the evidence of the expected resource(s), and of the appropriate protocol in the event of apparent discovery of an archeological resource;

· The archeological monitor(s) shall be present on the Project site according to a schedule agreed upon by the archeological consultant and the ERO until the ERO has, in consultation with Project archeological consultant, determined that Project construction activities could have no effects on significant archeological deposits;

· The archeological monitor shall record and be authorized to collect soil samples and artifactual/ecofactual material as warranted for analysis;

· If an intact archeological deposit is encountered, all soils-disturbing activities in the vicinity of the deposit shall cease.  The archeological monitor shall be empowered to temporarily redirect demolition/excavation/pile driving/construction activities and equipment until the deposit is evaluated.  If in the case of pile driving activity (foundation, shoring, etc.), the archeological monitor has cause to believe that the pile driving activity may affect an archeological resource, the pile driving activity shall be terminated until an appropriate evaluation of the resource has been made in consultation with the ERO.  The archeological consultant shall immediately notify the ERO of the encountered archeological deposit.  The archeological consultant shall make a reasonable effort to assess the identity, integrity, and significance of the encountered archeological deposit, and present the findings of this assessment to the ERO.

Whether or not significant archeological resources are encountered, the archeological consultant shall submit a written report of the findings of the monitoring program to the ERO. 

Archeological Data Recovery Program.  The archeological data recovery program shall be conducted in accord with an archeological data recovery plan (ADRP).  The archeological consultant, Project Sponsor, and ERO shall meet and consult on the scope of the ADRP prior to preparation of a draft ADRP.  The archeological consultant shall submit a draft ADRP to the ERO.  The ADRP shall identify how the proposed data recovery program will preserve the significant information the archeological resource is expected to contain.  That is, the ADRP will identify what scientific/historical research questions are applicable to the expected resource, what data classes the resource is expected to possess, and how the expected data classes would address the applicable research questions.  Data recovery, in general, should be limited to the portions of the historical property that could be adversely affected by the proposed project.  Destructive data recovery methods shall not be applied to portions of the archeological resources if nondestructive methods are practical.

The scope of the ADRP shall include the following elements:

· Field Methods and Procedures.  Descriptions of proposed field strategies, procedures, and operations.

· Cataloguing and Laboratory Analysis.  Description of selected cataloguing system and artifact analysis procedures.

· Discard and Deaccession Policy.  Description of and rationale for field and post-field discard and deaccession policies. 

· Interpretive Program.  Consideration of an on-site/off-site public interpretive program during the course of the archeological data recovery program.

· Security Measures.  Recommended security measures to protect the archeological resource from vandalism, looting, and non-intentionally damaging activities.

· Final Report.  Description of proposed report format and distribution of results.

· Curation.  Description of the procedures and recommendations for the curation of any recovered data having potential research value, identification of appropriate curation facilities, and a summary of the accession policies of the curation facilities.

Human Remains and Associated or Unassociated Funerary Objects.  The treatment of human remains and of associated or unassociated funerary objects discovered during any soils disturbing activity shall comply with applicable State and Federal laws.  This shall include immediate notification of the Coroner of the City and County of San Francisco and in the event of the Coroner’s determination that the human remains are Native American remains, notification of the California State Native American Heritage Commission (NAHC) who shall appoint a Most Likely Descendant (MLD) (Pub. Res. Code Sec. 5097.98).  The archeological consultant, Project Sponsor, and MLD shall make all reasonable efforts to develop an agreement for the treatment of, with appropriate dignity, human remains and associated or unassociated funerary objects (CEQA Guidelines. Sec. 15064.5(d)).  The agreement should take into consideration the appropriate excavation, removal, recordation, analysis, custodianship, curation, and final disposition of the human remains and associated or unassociated funerary objects.

Final Archeological Resources Report. The archeological consultant shall submit a Draft Final Archeological Resources Report (FARR) to the ERO that evaluates the historical significance of any discovered archeological resource and describes the archeological and historical research methods employed in the archeological testing/monitoring/data recovery program(s) undertaken.  Information that may put at risk any archeological resource shall be provided in a separate removable insert within the final report. 

Once approved by the ERO, copies of the FARR shall be distributed as follows: California Archaeological Site Survey Northwest Information Center (NWIC) shall receive one (1) copy and the ERO shall receive a copy of the transmittal of the FARR to the NWIC. The Major Environmental Analysis division of the San Francisco Planning Department shall receive three copies of the FARR (one copy will be in PDF OCR converted searchable text format) along with copies of any formal site recordation forms (CA DPR 523 series) and/or documentation for nomination to the National Register of Historic Places/California Register of Historical Resources.  In instances of high public interest in or the high interpretive value of the resource, the ERO may require a different final report content, format, and distribution than that presented above.

Alternative 3 – Central Subway Fourth/Stockton Alignment Option A (LPA)

Prehistoric Archaeological Resources. No construction impacts would affect known prehistoric resources within Alternative 3A. As a result of geoarchaeological analysis, described in detail in the HCASR (ASC 2007) and in Section 4.4 of this SEIS/SEIR, at least six locations of prehistoric archaeological sensitivity were identified in the Alternative 3A alignment. These locations, from south to north, are as follows:

· South of Market Street (in construction Reaches 6 and 5, King Street to I-80 overpass) has one location of varying sensitivity (one highly sensitive zone and one low), depending on depth;

· Reach 4, I-80 overpass to Folsom Street along Fourth Street, has one location of varying sensitivity (one highly sensitive zone and one low), depending on depth;

· Moscone Station has varying sensitivity (two moderately to highly sensitive zones and one low), depending on depth;

· Union Square/Market Street Station is highly sensitive;

· Chinatown Station is moderately to highly sensitive, depending on depth;

· Reach 1, Washington Street to Columbus Avenue and Union Street, has one highly sensitive location.

No specific evidence confirms that subsurface prehistoric cultural deposits are present; the sensitivity assessments are based on preliminary geoarchaeological research.

Historical Archaeological Resources.  One known historical archaeological resource may be affected by Project activities within this alternative.  CA-SFR-137H consists of the buried remains of a historic city block (bounded by Fourth, Fifth, Harrison, and Bryant Streets, and intermediate streets).  The location will be used for a construction yard. Resources include the archaeological remains of residential and commercial buildings, 1906 earthquake/fire debris, intact ground surfaces, and hollow-filled features from the 1870s.  The site is eligible to the NRHP/ CRHR under Criterion D/4.

The block-by-block historic overview, developed in the HCASR to predict areas of potential historical archaeological sensitivity, identified 15 locations at which archaeological resources may be encountered in the Alternative 3A alignment.  The locations, from south to north, and their potential affected property types include the following:

· The Fourth Street Portal is moderately sensitive for the presence of early historic refuse deposits in fill, which may also contain watercraft remains  (1840s-1850s);

· Moscone Station is highly sensitive for buried architectural remains, archaeological features, and/or sheet refuse  (1850s-1906);

· Union Square/Market Street Station has one location that is moderately sensitive for historic refuse deposits in fill (1840s-1850s), and one location highly sensitive for archaeological features, buried architectural remains, and/or sheet refuse (1850s-1860s);

· Union Square Station stairs location is moderately sensitive for early historic refuse deposits in fill (1840s-1854);

· Chinatown Station headhouse is highly sensitive for buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906);

· The two Chinatown Station emergency stair locations are each highly sensitive for buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906);

· The Tunnel has five locations that are highly sensitive for the presence of cisterns (1850s) and one location that is highly sensitive for wells and the artifacts they contain (1840s-1875);

· The TBM Retrieval Pit is moderately sensitive for the presence of historical archaeological park remains (1840s-1873).

Among the specific resources indicated by the block-by-block overview are artifact-rich fill and the remains of small watercraft from the 1840s to 1860s at the Fourth Street portal, within former marshlands and Mission Bay. Moscone Station headhouse construction may encounter archaeological deposits associated with commercial buildings and residences dating from the 1850s to 1906. At the Union Square/Market Street Station, a variety of deposits may be associated with a building constructed between 1852 and 1857 within the alignment of Stockton Street between O’Farrell and Ellis Streets, and sheet refuse and/or artifact caches below or within fill placed prior to 1854 at the intersection of Stockton, Ellis, and Market Streets. The Chinatown Station area has several potential resources: the Station headhouse may contain garden features, artifact caches, and architectural deposits; the Chinatown Station emergency stairs location may contain artifact-filled features dating to the Gold Rush era or earlier, prior to street paving; and beneath modern sidewalks may be architectural remains and archaeological features dating up to 1906, including basement room or niche extensions and tunnels of the type reported in San Francisco’s Chinatown and found elsewhere in California. Where Columbus Avenue cuts through City Block 117, tunneling may encounter wells backfilled with domestic or commercial artifacts between the Gold Rush and about 1873. Cisterns dating to the 1850s and extending to more than 20 feet below the surface may be present within Stockton Street at the intersections of Green, Vallejo, Broadway, Pacific, and Washington Streets; remnants may survive even if they were replaced. The TBM retrieval shaft in Columbus Avenue is within the former boundary of Washington Square created in 1848 and modified in 1873 when Columbus Avenue cut through it; deposits associated with the park may be present beneath the roadway.

Mitigation Measures

Mitigation measures would be the same as described for Alternative 2.

Alternative 3 – Central Subway Fourth/Stockton Alignment Option B (Modified LPA)

Prehistoric Archaeological Resources.  Construction would not affect known prehistoric resources within Alternative 3B. As a result of geoarchaeological analysis described in detail in the HCASR (ASC 2007) and summarized in Section 4.4 of this SEIS/SEIR, at least six locations of prehistoric archaeological sensitivity were identified of the Alternative 3B alignment. These locations, from south to north, are as follows:

· Reach 4, I-80 overpass to Folsom Street along Fourth Street, has both surface and subsurface components (both components are highly sensitive);

· The Moscone Station has varying sensitivity (one highly sensitive zone, one moderately to highly sensitive, and one low), depending on depth;

· Reach 3, Howard Street to Market Street along Fourth Street, has a surface component that is highly sensitive;

· Union Square/Market Street Station is highly sensitive;

· The Chinatown Station has one location that is moderately to highly sensitive;

· Reach 1, Washington Street to Columbus Avenue and Union Street, is highly sensitive.

No specific evidence confirms that subsurface prehistoric cultural deposits are present; the sensitivity assessments are based on preliminary geoarchaeological research.

Historical Archaeological Resources. One known historical archaeological resource is within Alternative 3B.  CA-SFR-137H consists of buried remains of a historic City block (bounded by Fourth, Fifth, Harrison, and Bryant streets, and intermediate streets). The location would be used for a construction yard. Resources include remains of residential and commercial buildings, 1906 earthquake/fire debris, intact ground surfaces, and hollow-filled features from 1870s. The site is eligible to the NRHP/ CRHR under Criterion D/4.

The block-by-block historic overview, developed in the HCASR to predict areas of potential historical archaeological sensitivity identified 13 locations where archaeological resources may be encountered in the Alternative 3B alignment. The locations, from south to north, and their potential affected resources include the following:

· Fourth Street—Moscone Station, Utilities relocation, and the Fourth Street Portal—is moderately sensitive for the presence of 1840s to 1860s refuse deposits in fill;

· Moscone Station is highly sensitive for the presence of buried architectural remains, archaeological features, and sheet refuse (1840s-1906);

· Union Square/Market Street Station has one location that is moderately sensitive for the presence of early historic refuse deposits in fill (1840s-1850s), for both station construction and utilities relocation, and one location that is highly sensitive for the presence of buried architectural remains, archaeological features, and/or sheet refuse (1850s-1860s);

· Chinatown Station headhouse is highly sensitive for the presence of buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906);

· Chinatown Station emergency stairs have one location that is highly sensitive for the presence of buried architectural remains, archaeological features, and/or sheet refuse (1840s-1906);

· The Tunnel has five locations that are highly sensitive for the presence of cisterns and the artifacts they contain (1850s), and one location that is highly sensitive for the presence of wells (1840s-1875) and their associated artifacts;

· The TBM Retrieval Pit is moderately sensitive for the presence of historical archaeological park remains (1840s-1873).

Among the potential specific resources indicated by the block-by-block overview are artifact-rich fill at the Fourth Street portal, within former marshlands and Mission Bay.  Moscone Station may encounter archaeological deposits associated with commercial buildings and residences dating from the 1850s to 1906.  A variety of deposits may be present at the Union Square/Market Street Station, associated with a building constructed between 1852 and 1857 within the alignment of Stockton Street between O’Farrell and Ellis Streets, and sheet refuse and/or artifact caches below or within fill placed prior to 1854 at the intersection of Stockton, Ellis, and Market Streets.  The Chinatown Station headhouse may contain garden features, artifact caches, and architectural remains; the Chinatown Station emergency stairs location may contain artifact-filled features dating to the Gold Rush era or earlier, prior to street paving; and beneath modern sidewalks may be architectural remains and archaeological features dating up to and including 1906, including basement room or niche extensions and tunnels of the type reported in San Francisco’s Chinatown and found elsewhere in California.  Where Columbus Avenue cuts through City Block 117, tunneling may encounter wells backfilled with domestic or commercial artifacts between the Gold Rush and about 1873.  Cisterns containing artifacts dating to the 1850s and extending to more than 20 feet below the surface may be present within Stockton Street at the intersections of Green, Vallejo, Broadway, Pacific, and Washington Streets; remnants may survive even if they were replaced. The TBM retrieval shaft in Columbus Avenue is within the original boundary of Washington Square as laid out in 1848 and until Columbus Avenue cut through it in about 1873; deposits associated with the park may be present beneath the roadway.

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2.

6.7.2 Historical Architectural Resources

In this section, impacts to buildings proposed for demolition and removal during construction are discussed first, followed by potential impacts to historic properties in each alternative, and then impacts to contributors of the NRHP, CRHR, and local historic districts.  It should be noted that although the Lower Nob Hill Apartment Hotel District is included within the Study Area, it is not located within an area proposed for stations or portals.  As a result, no impacts to the historic buildings in this district would result from the Project.

Alternative 2 – Enhanced EIS/EIR Alignment

One historic architectural resource located in the Chinatown Historic District would be demolished and replaced by a new Muni station building during construction of the Enhanced EIS/EIR Alignment (there are 371 contributing buildings in the Chinatown Historic District). The building at 814-828 Stockton Street (Assessor’s Parcel No. 225-014) was identified as a Class 3D contributor to the NRHP-eligible and CRHR-listed Chinatown Historic District during the Corbett et al. (1997) study for the Third Street Light Rail EIS/EIR in 1998 (see Figure 6-17).  Demolition of contributing elements to a NRHP-eligible district

Figure 6-17

814-828 Stockton Street proposed for demolition

under Alternatives 2 and 3A

Source:  PB/Wong

constitutes an adverse effect under Section 106 of the National Historic Preservation Act of 1966 and under the California Environmental Quality Act.  Within Block 225, each of the three remaining buildings on the east side of Stockton Street, is also contributing elements to the historic district, as are properties on the west side of the street.  Proposed demolition of the building on the east side of Stockton Street would create a visual break in this cohesive grouping of related buildings that are contextually important to the Chinatown Historic District.  The colorful awnings and signage demarcating the store fronts along Stockton Street, each contribute to the cohesive unit of buildings along this block between Sacramento and Clay Streets.  Removal of this building with its character-defining features and history of use by businesses (Chinese school and newspaper) important to the Chinese community would adversely affect the Historic District. 

In addition to the Chinatown Station, significant historic architectural resources identified in the APE (see Denardo et al. 2007) for this Alternative would be temporarily affected by the visual presence of construction equipment and could have vibration effects from construction of the Enhanced EIS/EIR Alignment.  Construction-related activities could result in ground shifts (settlement) that would affect adjacent properties determined as eligible for listing on the NRHP.  The areas most prone to settlement effects would be where cut-and-cover construction methods are implemented, including the station areas and portals.  This construction method involves a trench excavation using secant pile ground-supporting walls and construction of a box frame structure.  Equipment for this process would include heavy construction vehicles, 80-foot high augers and cranes for a period of approximately two to six months.  Settlement would be stabilized after the supporting walls have been installed.  (See also: Section 6.15, Noise and Vibration.)

Some of the historic architectural resources are contributors to NRHP-eligible districts crossed by this Alternative, others are individual properties that are NRHP-eligible on their own merit (see Appendix F).  These are described below.

Northbound Portal and Third Street Surface Tracks.  Six historic buildings, including 660-670 Third Street, 689-699 Third Street, 679-685 Third Street, 665 Third Street, 625 Third Street, and 601 Third Street, were identified as NRHP-eligible contributors to the South End Historic District.  Each has the potential for temporary vibration and visual impacts from construction of the Third Street surface tracks under Alternative 2, depending on the fragility of the building.  Two additional historic architectural resources, 566-586 Third Street and 500 Third Street, are outside of the historic district but are individually eligible for the NRHP.  Expected effects would be limited to minor architectural damage.  No structural damage is expected. Visual impacts would be limited to the duration of construction.

Southbound Portal and Fourth Street Surface Tracks.  One historic architectural resource at 508-514 Fourth Street, in the southbound tunnel portal area along Fourth Street, has the potential for temporary vibration impacts during construction and visual impacts from the presence of construction equipment.  The building is not in a historic district, but is eligible for an individual listing on the NRHP.

Market Street Station.  In the Market Street Station area for Alternative 2, there are five significant historic architectural resources.  Due to the depth of the construction at this location there is little potential for impacts from ground-borne vibration during construction of the station. None of the resources are associated with a historic district, but all are individually NRHP-listed or -eligible.  700-706 Mission Street and 703-705 Market Street (26 Third Street) front Third Street on the west side of the proposed Market Street Station.  Three more historic architectural resources, including 17-29 Third Street, 691-699 Market Street, and 673-687 Market Street, are all individually NRHP-eligible, and each is on the east side of Third Street.  Two are in the first parcel next to the proposed station, and the third is in the second row.

Union Square Station.  In the Union Square Station area, there are eight significant historic architectural resources.  Due to the depth of the construction at this location there is little potential for impacts from vibration during construction of the station.  All eight properties are within the boundaries of the KMMS Conservation District, and each is also eligible for listing on the NRHP as an individual property.  They include 218-222 Stockton Street, 234-240 Stockton Street, 275-299 Post Street, 278-298 Post Street, 177-179 Maiden Lane, 259 Post Street, and 272 Post Street; they comprise four properties fronting the station and another three in the second row.  The presence of construction activities would temporarily affect the historic visual character of the block, but would not affect individual properties.

The eighth property, Union Square (the plaza and the underground parking garage) serves as the heart of the KMMS Conservation District.  Union Square is eligible for listing on the NRHP as an individual property and it is listed as California State Landmark No. 623. As with the other properties, it would have little potential for impacts from vibration during deep station excavation and tunneling.  The visual presence of construction equipment and traffic barriers and signage would temporarily affect the Union Square landscape, but would not be considered a significant adverse affect because of the temporary nature of the disturbance.  (See also Section 5.3.3 Visual Impacts.)  Union Square is a City park, and is therefore subject to Section 4(f) analysis and approval (See Chapter 10.0).  

Chinatown Station.  In the Chinatown Station area, there are nine significant historic architectural resources, in addition to the station buildings at 814-828 Stockton Street.  Due to the depth of the construction at this location there is little potential for vibration impacts from construction of the station, including eight properties that front the proposed station and one in the second row.  They include 801-805 Stockton Street, 800-810 Stockton Street, 809-815 Stockton Street, 827-829 Stockton Street, 830-848 Stockton Street, 833-841 Stockton Street, 843 Stockton Street, 850-898 Stockton Street and 857-865 Clay Street.  Each of these properties is eligible for listing on the NRHP as a contributing element of the Chinatown Historic District.  Temporary construction-related impacts to this cohesive group of buildings in this historic district would primarily be related to visual disturbance from construction activities.

Mitigation Measures

Ground-borne vibration levels are generally not expected to impact historic buildings structural integrity, however, older buildings built with less stringent building codes (such as in the Chinatown area) would be more susceptible to minor architectural damage (trim, window casings, brick chimneys) during construction activities. 

Potential effects of vibration during construction would be greatly reduced by pre-drilling for pile installation in areas that would employ secant piles with ground-supporting walls in the cut-and-cover technology.  Vibration monitoring in historic districts adjacent to tunnel portals and stations will be specified in construction documents to ensure that historic properties do not sustain damage during construction.  A mitigation monitoring plan to ensure that vibration impacts to historic buildings would be mitigated would include the following: 

1. The contractor will be responsible for the protection of vibration-sensitive historic building structures that are within 200 feet of any construction activity, [begin deletion] including unreinforced masonry buildings [end deletion] . 

2. The maximum peak particle vibration (PPV) velocity level, in any direction, at any of these historic structures should not exceed 0.12 inches/second for any length of time. 

3. [begin insertion] The contractor [end insertion] [begin deletion] An independent Environmental Compliance Monitor (ECM) will be retained by SFMTA to monitor construction to make sure that environmental conditions are met.  The ECM [end deletion] will be required to perform periodic vibration monitoring at the closest structure to ground disturbing construction activities, such as tunneling and station excavation, using approved seismographs. 

4. If at any time the construction activity exceeds this level, that activity will immediately be halted until such time as an alternative construction method can be identified that would result in lower vibration levels.

5. [begin deletion] The ECM will conduct a training program at the start of construction to educate the Contractor and consultants about the sensitivity of historic structures to construction related vibration. [end deletion]

In compliance with the Secretary of the Interior’s Standards for the Treatment of Historic Properties, an adverse effect is found when an undertaking alters, either directly or indirectly, the character-defining features of a NRHP-eligible property.  However, adverse impacts can be reduced through rehabilitation,

context-sensitive designs, and measures to record and preserve for posterity the history of the building and its uses.

Because demolition of the building at 814-828 Stockton Street under the Alternative 2, Enhanced EIR/EIS Alternative would constitute an adverse effect to a contributing property in the Chinatown Historic District, the following mitigation measures to reduce adverse effects are proposed:

1. Partial preservation of 814-828 Stockton Street, through rehabilitation, in compliance with the Secretary of the Interior’s Standards, and reuse of the building as the Chinatown Station. 

2. Include expertise of an architectural historian in design development of station [begin deletion] to develop a design culturally appropriate to the Chinatown community [end deletion] .

3. Salvage of the significant architectural features from 814-828 Stockton Street to be used as an educational exhibit inside the new station or utilized for the repair and rehabilitation of other historic buildings.  The architectural elements will be disassembled in a manner that minimizes damage.

4. In consultation with the City, FTA, and SHPO, develop a permanent interpretive display for public use on the entire route, perhaps to be placed within the subway cars or on the walls of the subway stations.  This interpretive display would include details about the demolished buildings as well as historic information about the buildings, historic districts, neighborhoods, important individuals, and businesses surrounding the alignments that the Central Subway will pass through.  Prior to preparing the display, a qualified historian will perform contextual research regarding the role of the building in the events for which it is significant, and conduct oral history interviews. This approach would impart knowledge of the history of the City to the general public.

Although this would not be considered [begin insertion] a [end insertion] mitigation [begin deletion] to a less-than-significant effect [end deletion] [begin insertion] measure [end insertion] , if the historic building at 814-828 Stockton Street is demolished, then it would be standard practice to perform Historic American Buildings Survey/Historic American Engineering Record (HABS/HAER) documentation.   Because it is presently uncertain who the architect was for 814-828 Stockton Street, attempts should be made to obtain the original drawings, if available.  The level of documentation will be prescribed through consultation with the City Historic Preservation Officer, FTA, and SHPO for conservation.

Alternative 3 – Fourth/Stockton Alignment Option A (LPA)

Construction of Alternative 3A would have the same impacts as described above for Alternative 2 because the building identified for the Chinatown Station is the same building as described for Alternative

2 (814-828 Stockton Street), except for the North Beach Construction Variant.  The areas where cut-and-cover methods would be implemented, including the station areas, tunnel portals, and the Tunnel Boring

Machine extraction shaft in North Beach could result in minor architectural damage (not structural damage)to historic buildings near the station.

Significant historic architectural resources were identified in the APE that could be affected by construction of Alternative 3A (see Denardo et al. 2007).  Some of the historic architectural resources are contributors to NRHP-eligible districts, while others are individual properties that are NRHP-eligible on their own merit (see Appendix F).  The properties and potential impacts are described below.

Northbound/Southbound Portal.  The NB/SB tunnel portal construction area on Fourth Street includes one significant historic building at 601 Fourth Street.  The building is eligible for an individual listing on the NRHP.  Temporary visual impacts from the presence of construction equipment would be limited to the duration of construction and would not adversely affect this property.

Union Square/Market Street Station.  In the Union Square/Market Street Station area, fourteen significant historic architectural resources have the potential for temporary impacts from ground-borne vibration from construction equipment and activities.  Each of the properties is within the boundaries of the KMMS Conservation District, and each is eligible for listing on the NRHP as an individual property.  They include 233 Geary Street, 101 Stockton Street, 150 Stockton Street, 160-170 Geary Street, 218-222 Stockton Street, 234-240 Stockton Street, 275-299 Post Street, 177-179 Maiden Lane, 259 Post Street, 760 Market Street/35 O’Farrell Street (Phelan Building, Landmark No. 156), 2 Stockton Street, 77-81 O’Farrell Street, and 79 O’Farrell Street (formerly 46-68 Stockton/77-79 O’Farrell).  Nine of the buildings front the station and four are in the second row.

As described above for Alternative 2, Union Square, including the underground parking garage, is eligible for listing on the NRHP as an individual property in addition to being included in the KMMS Conservation District.  Along the eastern end of the Union Square plaza there would be a pedestrian entry within the stairs leading to the plaza.  It would consist of escalators, stairs, with the possibly of an overhead canopy.   Two vent shafts, with heights of 11 feet, would be positioned within the plaza terrace below the plaza café.   These alterations would not constitute substantial adverse impacts to the historic character of the KMMS conservation district, or to Union Square, which was renovated in 2002.

Chinatown Station.  Demolition of the building at 814-828 for the proposed Chinatown Station is the same as that described above for Alternative 2.  Impacts in the Chinatown Historic District would be the same as those described above for Alternative 2.

Tunnel Boring Machine Extraction Shaft.  Under the North Beach Construction Variant, an extraction shaft would be located in the middle lanes of Columbus Avenue at the north end of the alignment to allow for removal of the Tunnel Boring Machine (TBM).  The construction would be similar to the cut-and-cover method.  Of the properties in the impact area, Washington Square Park and the associated Washington Square Park Triangle are the only resources in close proximity to the extraction shaft.  Washington Square Park is listed as locally significant -- both individually as San Francisco’s Landmark No. 226, and as a contributor to a proposed historic district.  There would be no vibration impacts to the park and visual impacts would be limited to the duration of construction and would not substantially impact park use or historic integrity.

Five additional properties, considered contributors to the proposed Washington Square Historic District, are located within 200 feet of the extraction shaft.  The buildings include 1636-1656 Powell Street, 575-579 Columbus Street, 1731-1741 Powell Street, 1717-1719 Powell Street, and 1701-1711 Powell Street.  Because of the distances from the extraction shaft and the temporary nature of construction activity, there would not be vibration impacts to any of the historic buildings.

Mitigation Measures

The same mitigation measures would apply as those described for Alternative 2.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

One historic architectural resource (out of 14 historic buildings in the block and 371 contributing buildings in the Chinatown Historic District) located in the Chinatown Station area would be demolished and replaced by a new Muni station building during construction of the Alternative 3B.  The building at 933-949 Stockton Street (Block 211) was identified as a Class 3D contributor to the NRHP-eligible Chinatown Historic District during the Corbett et al. (1997) study (see Figure 6-18).  Demolition of contributing elements to a NRHP-eligible district constitutes an adverse effect under Section 106 and under the California Environmental Quality Act.  Demolition and removal of the proposed building would create a visual break in the cohesive grouping of related buildings.  Also within Block 211, eight additional buildings on the west side of Stockton Street are also contributing elements to the Chinatown Historic District, and significant properties are on the adjacent block (Block 192) fronting Washington Street.  The high rise building (Mandarin Tower) on the east side of Stockton Street, directly across from 933-949 Stockton Street, in Block 210, is not historic and by its dominant presence has altered the visual continuity of this block of Chinatown. 

The proposed station location at 933-949 Stockton Street and the buildings surrounding it are contextually linked through their association with the development of the Chinatown community. The building lies within an area known to be a part of Chinatown since at least the 1880s and has continuously remained a vibrant part of the community.  Designed by S. H. Woodruff and erected in 1906, 933-949 Stockton

Figure 6-18

933-949 Stockton Street proposed for demolition

under Alternative 3B

Source:  Garcia and Associates

Street served the immediate need for lodging and shop space by Chinese merchants in the aftermath of [begin insertion] a [end insertion] [begin deletion] the 1906 [end deletion] natural disaster.  933-949 Stockton Street conforms to the two-part commercial block composition also found in other areas of San Francisco.  Its character-defining features include the Renaissance/Baroque design elements that include swags over the windows, metal cornice, and scored stucco walls.

Within the block (Block 211), the three remaining buildings on the west side of Stockton Street are also contributing elements to the historic district, and other important buildings are nearby, including the Commodore School, the Chinese Methodist Episcopal Church, [begin deletion] Presbyterian Church in Chinatown, [end deletion] and the Gum Moon Residence.   Removal of the building at 933-949 Stockton Street for construction of a Muni station would break up the continuity of contextually and architecturally linked buildings and would adversely affect the NRHP eligible historic district. 

In addition to the station, construction of the Alternative 3B also has the potential for ground settlement near other stations and near the tunnel portals caused by construction-related activities could result in localized ground shifts that would affect historic architecture.  The areas most prone to settlement would be where cut-and-cover methods are implemented, including the station areas, tunnel portals, and extraction shaft.  The same construction methods described for Enhanced EIS/EIR Alignment would also apply to Alternative 3B at stations and tunnel portals.

Significant historic architectural resources were identified in each potential impact area that could be affected by the Project (see Denardo et al. 2007).  Some of the historic architectural resources are contributors to NRHP-eligible districts, while others are individual properties that are NRHP-eligible on their own merit (see Appendix F).  These are described below.

Bryant/Brannan Station.  The Bryant/Brannan Surface Station on Fourth Street would be adjacent to two historic architectural resources that have the potential for minor architectural damage from vibration during construction at 500-504 Fourth and 508-514 Fourth.  Each of these buildings is eligible for an individual listing on the NRHP.  This minor temporary effect would not adversely effect the properties or District.  The design of the surface platform at Bryant and Brannan Streets would be compatible with existing Muni stations south of Market Street and would not adversely affect the visual character of the Historic District or individual historic properties.

Union Square/Market Street Station.  Under Alternative 3B, the station entry is proposed for the southeast side of Union Square, along Geary Street, rather than along Stockton Street.  In the Union Square/Market Street Station area, approximately eight significant historic architectural properties have the potential for minor architectural damage from construction-related vibration during station excavation operations, including seven properties (six buildings and Union Square) fronting the station and one property in the second row.  This temporary impact would not result in a significant adverse effect to the individual properties or to the historic district and would not affect the historic use of the park or garage

All eight properties are within the boundaries of the KMMS Conservation District, and each is eligible for listing on the NRHP as an individual property.  They include 233 Geary Street, 101 Stockton Street, 760 Market Street/35 O’Farrell Street (Phelan Building, Landmark No. 156), 2 Stockton Street, 77-81 O’Farrell Street, 79 O’Farrell Street (formerly 46-68 Stockton/77-79 O’Farrell), 150 Stockton Street and 333 Post Street (Union Square).  All of these properties are in the first row fronting Stockton Street except for 760 Market/35 O’Farrell Street, which is in the second row.  No significant adverse effects to historic properties would result from construction of Alternative 3B, though temporary construction-related visual and vibration effects have been noted.

Chinatown Station.  In addition to the building identified for demolition for the station, other historic properties in the APE have been analyzed for potential impacts.  The proposed station for Alternative 3B differs from that of Alternatives 2 and 3A.  Rather than mid-block along the east side of Stockton Street, the station location for this alternative would be at the corner of Stockton Street and Washington Street, a block north of the other alternatives.  In the Chinatown Station area for this alternative, there are fourteen significant historic architectural resources that have the potential for construction-related impacts.  They include seven properties that front the proposed station, six in the second row, and one in the third row.  In addition, the Washington Street Street Lights are a significant historic architectural resource that could be impacted by temporary ground-borne vibrations and other construction equipment and activities at the Chinatown Station site for this alternative. Each of these properties is eligible for listing on the NRHP as a contributing element of the Chinatown Historic District and one is eligible for listing on the NRHP as an individual property (940 Washington Street).

There are six buildings in the same block as the station (Block 211), and include three that front Stockton Street (901-907 Stockton Street, 913-917 Stockton Street, and 925 Stockton Street), two in the second row (910-914 Clay Street and 950 Clay Street), and one in the third row (916-918 Clay Street), which is two buildings away from the station.  Chinatown Historic District contributing buildings across Stockton Street include 930 Stockton Street in the first row, and 868-870 Clay Street, 31-37 Spofford Alley, and 867-869 Washington Street in the second row.  Across Washington Street from the building at 933-949 Stockton Street proposed for demolition, there are two buildings in the first row (1003-1011 Stockton Street and 940 Washington Street), and one contributing building (1013-1017 Stockton Street) in the second row. As indicated above, 940 Washington Street appears to be eligible for listing on the NRHP as an individual property. 

Other than the property proposed for demolition at 933-949 Stockton Street, temporary construction-related vibration and visual impacts would not have significant adverse effects to historic properties or the historic Chinatown District.

Tunnel Boring Machine Extraction Shaft.  Impacts for the North Beach Construction Variant for Alternative 3B would be the same as those described above for Alternative 3A and would not have the potential for adverse effects to historic properties.

Mitigation Measures

Mitigation measures would be the same for Alternative 3B as those described above for Alternative 3A.  The mitigation measures identified for 814-828 Stockton Street under Alternative 2 would also apply to 933-949 Stockton Street for this alternative.

To ensure that the historic Street Lights are not impacted by vibration and construction equipment, the Contractor will implement a mitigation plan to ensure that vibration impacts to the historic lights would include the following: 

1. The contractor will be responsible for the protection of vibration-sensitive historic street lights that are within 50 feet of any construction activity. 

2. The plan would include temporary removal and storage of glass globes during construction in a specific area and installation of construction barriers adjacent to the light poles.

Although this should not be considered [begin insertion] a [end insertion] mitigation [begin deletion] to a less-than-significant effect [end deletion] [begin insertion] measure [end insertion] , if the historic building at 933-949 Stockton Street is demolished, then it would be standard practice to perform Historic American Buildings Survey/Historic American Engineering Record (HABS/HAER) documentation.   It is known that S. H. Woodruff was the architect for 933-949 Stockton Street; attempts should be made to obtain the original drawings, if available.  The level of documentation will be prescribed through consultation with the City Historic Preservation Officer, FTA, and SHPO.

6.8 construction impacts and mitigation measures for visual and aesthetic resources

Alternative 2 - Enhanced EIS/EIR Alignment

Heavy equipment (augers, cranes, drilling rigs, backhoe, and excavators) would be transported to the site from the staging area, located under the I-80 elevated freeway structure near Fourth and Bryant Streets. Use of the staging area would be consistent with previous uses for construction in the area and would not have visual impacts.  In those sections of the Enhanced EIS/EIR Alignment having cut-and-cover construction, 80‑foot high augers and cranes, k-rails and construction safety barriers would temporarily change the streetscape along Third and Fourth Streets, in the South of Market area.  Similar equipment would also be used at the tunnel portals and at station locations for excavation and to construct retaining walls. The presence of construction equipment in this rapidly developing area of the City (South of Market) has been common over the past several years and would not distract from the dominant building features that line Third and Fourth Streets.  The temporary presence of construction equipment at the Moscone, Union Square, and Chinatown station locations would be highly visible from these heavily used areas and would temporarily degrade and obstruct public views of these landscapes.  Night lighting at construction sites would be directed at the work site and shaded to prevent glare to adjacent residential units.  Trees would not be removed during construction for this alternative.   

Mitigation Measures

Though no significant adverse visual impacts have been identified, improvement measures to minimize potential visual contrasts of Project features with surrounding landscape features include:  use of screening around staging areas and excavation sites during construction and directional shading of night lights to minimize glare to residential buildings.  Excavated materials would be hauled off daily, rather than stored on-site.

In visually sensitive landscapes, like historic Union Square and Chinatown, use of temporary screening or physical barriers (noise walls) around the station construction sites is suggested to further reduce temporary visual effects during construction.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction equipment for this alternative would be the same as that described for Alternative 2 above and would have temporary construction-related visual effects. Since this alternative would not use Third Street, construction-related impacts would be concentrated on Fourth Street, south of Market Street, where tunneling equipment would enter the underground work area.  Temporary screening of the work area would be used to control dust and minimize views of construction equipment and construction materials.  Excavated materials would be hauled off daily rather than stored on-site.  The same as Alternative 2 above, the temporary presence of construction equipment at the Moscone, Union Square, Market Street, and Chinatown station locations would be highly visible and would temporarily effect  public views of these visual resources.

The North Beach Tunnel Construction Variant includes a temporary excavation shaft at Columbus Avenue, north of Union Street, and adjacent to Washington Square Park, that would be used for the removal of Tunnel Boring Machines and other construction equipment and supplies. The presence of heavy construction equipment, with associated noise and dust effects would have temporary construction-related visual impacts because it would be visible from the west side of the park and adjacent sidewalks.  This would result in temporary visual and aesthetic impacts that could affect the scenic vistas from of the park for the duration of construction. 

If the North Beach Tunnel Construction Variant is not approved, the excavation shaft during construction would be at the Chinatown Station described above.  Temporary construction-related impacts described for the station above would occur.

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Construction-related visual impacts for this alternative would be the same as those described for Alternative 2 and Alternative 3A above.  Temporary screening of the work area would be used to control dust and minimize views of construction equipment and debris.  Excavated materials would be hauled off daily, rather than stored on-site. 

The North Beach Tunnel Construction Variant described above for Fourth/Stockton Alignment Option A, could also be part of the Fourth/Stockton Alignment Option B and would have the same impacts.  The excavation shaft at Columbus Avenue, north of Union Street, and adjacent to Washington Square Park, would have temporary construction-related visual impacts because it would be visible from the west side of the park and adjacent sidewalks. 

If the North Beach Tunnel Construction Variant is not approved, the excavation shaft would be at the Chinatown Station site described above and impacts would be the same as those described for the station.

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

6.9 construction impacts and mitigation for UTILITIES AND ENERGY

6.9.1 utilities

Alternative 2 - Enhanced EIS/EIR Alignment

The Enhanced EIS/EIR Alignment proposes the use of Special Excavation Method (SXM) for the transit tunnels between stations. The construction of SXM soil-cement walls would require the relocation of sub-surface utilities located parallel to and beneath the walls.  Utilities above the guideway tunnels that are sensitive to ground movement or are densely congested would need to be relocated to allow the jet grouting operations to take place.  The crossing of Market Street is one area where utilities are particularly congested.  The SXM construction approach is described more fully in Section 6.1.4.

The Enhanced EIS/EIR Alignment would utilize decked cut-and-cover construction for Union Square Station, Market Street Station, Moscone Station, and portals on Third and Fourth Streets between Bryant and Brannan Streets. Cut-and-cover construction would require relocation of all utilities within the cut-and-cover footprint.  Service laterals between the walls and utilities in street crossings intercepted by these walls would also be affected by both cut-and-cover construction and SXM construction.

In addition to the general impacts described above, construction at the Market Street Station on Third Street would displace a 96-inch North Point trunk sewer line, which would cross the Enhanced EIS/EIR Alignment at Mission Street.  The relocation of this sewer trunkline would be critical because of the size and the importance of this sewer facility.  In order to maintain the function and capacity of the North Point sewer line, the sewer could be diverted under the subway at Third and Mission Streets.  If this approach were implemented by Muni as a condition of Project construction, an underground siphon and pumping station would be installed to force the effluent to flow under the subway.  During dry weather, a low-flow pipe would divert effluent from the existing sewer line into the pump station’s wet well vault located below the subway under the Mission/Third Streets intersection.  The pumps would force the effluent to continue to move from west to east passing through the siphon into the existing trunk sewer line.  Pumping action would be controlled to prevent the pooling and standing of water in the siphon.  During storm events, effluent would flow through the siphon by hydraulic pressure.  Resources required to operate and maintain this facility would be identified during design.  Alternatively, the sewer line could be rerouted by Muni south along Fourth Street to Folsom Street, east on Folsom to Second Street, and north on Second to Mission Street.  To minimize traffic impacts, the sewer would be rerouted using tunneling construction procedures.  Utilities in areas where SXM is used  would be relocated to utility corridors located between the soil-cement walls and property line. Joint trenches would be constructed to maximize the use of the limited space between the new work and adjacent properties.

Utilities at cut-and-cover station locations would be relocated to a utility corridor within or adjacent to the station structure.  Utilities and service laterals intercepted as a result of installation of soil-cement walls would be connected to temporary or permanent utility mains installed between the new work and adjacent properties or routed around the new work to tie into existing mains.

There would be minimal impacts to utilities at the Chinatown Station, which would be mined 25 to 35 feet below the surface.  Utilities located in the street or sidewalk above would not be disturbed.  The entrance to this station would be in a private parcel that Muni would acquire.  A construction shaft would be excavated at this entry site for access to the underground station.  Construction activities would not affect public or private utilities except for private parcel connections to main utility lines.  There would be minimal impact to some utilities (see Section 4.6) at a sidewalk bulb-out that would be the site of an emergency stairway.

Utility relocation would require street and sidewalk excavations that would impact traffic and pedestrian flow in the areas adjacent to the relocation activities.  These areas would include station and tunnel segments mentioned above. Utility relocation in sidewalks may require access to or use of existing basements located beneath the sidewalks.  Property owners with sub-sidewalk basements may be required to vacate these basements to make room for relocated utilities.

Utilities located beneath surface trackway would require relocation, strengthening or protection.

Utility service disruptions would likely occur for short periods of time when new relocated utilities are tied into the existing utility systems. As indicated in Section 6.2, utility relocation would occur over an 24-month period for the Enhanced EIS/EIR Alignment. 

Mitigation Measures

Utility relocation coordination would take place during detailed design in consultation with the utility agencies and the design team and would be phased to ensure that pedestrian and vehicular traffic flows are maintained.  No further mitigation would be required.  All utilities would be properly relocated and service would be restored as part of the Project.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option A (LPA)

TBMs would be used to construct the guideway tunnels between the stations.  This construction methodology would not require those utilities above the TBM tunnels to be relocated.  If the North Beach Construction Variant is adopted, utilities on Columbus Avenue, between Union and Filbert Streets, would need to be diverted to facilitate construction for the TBM retrieval shaft.

Alternative 3A will utilize cut-and-cover construction for Moscone Station, Union Square/Market Street Station, and the portal on Fourth Street between Townsend and Brannan Streets, as well as at emergency stairways at all the stations.  The construction of retaining walls (either secant pile or slurry wall construction) at these cut-and-cover locations would require numerous utility relocations.  Service laterals intercepted by the retaining walls, and utilities in street crossings intercepted by these walls, would also be affected.

The same as described for Alternative 2 above, there would be minimal impacts to utilities at the Chinatown Station, which would be mined 25 to 35 feet below the surface. 

Temporary and permanent surface penetrations, such as construction shafts, portals, station entrances (stairs, escalators, elevators) and emergency stairways, would require rerouting of utilities that cross those penetrations.  Utility relocation would require street and sidewalk excavations that will temporarily impact traffic and pedestrian flow in the areas adjacent to the relocation activities.  Utility relocation in sidewalks may require access to existing basements located beneath the sidewalks.  Property owners with sub-sidewalk basements may be required to vacate these basements to make room for relocated utilities.

Utilities located beneath surface trackway would require relocation, strengthening or protection. 

Cut-and-cover construction would provide temporary decking installed after initial excavation to such a depth that spoils can be removed from a construction shaft.  Some utilities could be suspended from this temporary decking.  Other utilities would be relocated to utility corridors located between the retaining walls and property line.  Joint trenches would be constructed to maximize the use of the limited space between the new work and adjacent properties.  Utilities and service laterals intercepted as a result of installation of the retaining walls (secant piles or slurry walls) would be connected to temporary or permanent utility mains installed between the new work and adjacent properties or routed around the new work to tie into existing mains.

Utility service disruptions would likely occur for short periods of time when new relocated utilities are tied into the existing utility systems.  Utilities affected by construction of the Central Subway Fourth/Stockton Alignment Option A are described in Section 4.6.  As indicated in Section 6.2, utility relocation would commence in advance of heavy civil construction work for the guideway and stations and would occur over a six month period for the Central Subway Fourth/Stockton Alignment Option A.

Mitigation Measures

Mitigation measures would be the same as identified above under Alternative 2.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option B (Modified LPA)

The utility impacts for Alternative 3B would be the same as for Alternative 3A, except as noted below.

Cut-and-cover construction methodology would require excavation from the surface, thereby affecting all utilities within the cut-and-cover area.  Service laterals to adjacent properties would be cut by retaining wall construction.  Temporary and permanent surface penetrations, such as construction shafts, portals, station entrances (stairs, escalators, elevators) and emergency stairways, would require rerouting of utilities that cross those penetrations.

Utility relocation would require street and sidewalk excavations that would impact traffic and pedestrian flow in the areas adjacent to the relocation activities.  Utility relocation in sidewalks may require access to existing basements located beneath the sidewalks.  Property owners with sub-sidewalk basements may be required to vacate these basements to make room for relocated utilities.

Utilities located beneath surface trackway would require the relocation, strengthening or protection.

Cut-and-cover construction at station locations would provide temporary decking installed after initial excavation to such a depth that spoils can be removed from a construction shaft.  Some utilities could be suspended from this temporary decking.  Other utilities would be relocated to utility corridors located between the retaining walls and property line.  Joint trenches would be constructed to maximize the use of the limited space between the new work and adjacent properties.  Utilities and service laterals intercepted as a result of installation of the retaining walls  would be tied into temporary or permanent utility mains installed between the new work and adjacent properties or routed around the new work to tie into existing mains.

Utility service disruptions would likely occur for short periods of time when new relocated utilities are tied into the existing utility systems.  Utilities affected by construction of the Central Subway Fourth/Stockton Alignment Option B are described in Section 4.6.   As indicated in Section 6.2, utility relocation would occur over a six month period for the Central Subway Fourth/Stockton Alignment Option B. 

Mitigation Measures

The mitigation measures would be the same as described for Alternative 2.

6.9.2 energy

Alternative 2 – Enhanced EIS/EIR Alignment

Fuel consumption associated with operation of construction vehicles and machinery would occur during the construction phase.  Fuel consumption to power construction equipment could be accommodated with existing energy resources.  This temporary consumption of energy would not result in an energy impact.

Mitigation Measures

No mitigation measures would be required.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction impacts would be the same as described for Alternative 2 above.

Mitigation Measures

No mitigation measures would be required.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Construction impacts would be the same as described for Alternative 2 above.

Mitigation Measures

No mitigation measures would be required.

6.10 constuction impacts and mitigation for geology and seismicity

6.10.1 geologic hazards

Alternative 2 - Enhanced EIS/EIR Alignment

During construction of the Enhanced EIS/EIR Alignment, an earthquake could occur.  The associated groundshaking could affect the areas under construction and the safety and health of the construction workers.  Construction of underground tunnels, shafts, and excavations will be conducted in accordance with all applicable federal, state and local codes and practices.  The federal regulations are included in Part 1926, Section 800 of Title 29 of the Code of Federal regulations (29 CFR 1926.800) which is administered by the Occupational Safety and Health Administration (OSHA) and covers the safety and health of underground workers.  California regulations are documented in Title 8 of the California Code of Regulations and are enforced by Cal/OSHA. 

Muni would require contractors to submit a site-specific earthquake preparedness and emergency response plan as part of compliance with bid specifications.  The plan would include specification by an emergency coordinator/team, provisions for emergency power and communication, evacuation procedures, and post-earthquake safety inspection.  As part of the MTA’s procedures and guidelines, Muni has developed a working document that covers earthquake preparedness and post-earthquake inspection/ repair procedures.

Mitigation Measures

No mitigation measures would be required.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA) and Option B (Modified LPA)

Construction impacts would be the same as described above for Alternative 2.

Mitigation Measures

No mitigation measures would be required.

6.10.2 settlement or instability of subsurface materials

Alternative 2 - Enhanced EIS/EIR Alignment

This alternative includes installation of subway tunnels and stations with off-street entries and vent shafts on Third, Fourth, and Harrison Streets (north of Brannan Street), connecting under Market Street and along Kearny and Geary Streets to Stockton Street and continuing north to Clay Street.  South of Brannan Street, tracks would be constructed on the surface of Third and Fourth Streets.  Unless considered during the design, excavation of the tunnel and stations (either through mining or cut-and-cover) through the developed Downtown area could result in potential settlement of geologic materials surrounding the excavation during construction.  Under Alternative 2, construction of the tunnels over the upper pair of Market Street tunnels (Muni) would be expected to reduce ground loads acting on the tunnel lining, resulting in an upward ovaling distortion similar to that experienced on the BART tunnels during the Muni Metro turnarounds.  Limited dewatering of the cut-and-cover areas would reduce potential settlement of water bearing subsurface layers. Construction-period settlements could cause damage to existing building foundations, subsurface utilities, and surface improvements (e.g., sidewalks and roadways).

Based on preliminary geotechnical investigations of subsurface materials along the alignment, tunneling would encounter a variety of geologic materials, including artificial fill, dune sand, Bay Mud, undifferentiated Old Bay deposits, colluvium, dense sand (Colma Sand) and bedrock (see Figure 5-14).[2]  Preliminary geotechnical reports prepared for the mined and cut-and-cover tunneling portions of the Project include recommendations for management of potential construction-period settlements. ^[3],[4]  Site specific designs to limit potential construction-period settlements would be addressed in detail in the design-level geotechnical analyses that would be prepared for the Project.  These analyses would include detailed evaluations of the site-specific geotechnical properties of the subsurface materials; building-by-building evaluations of foundations that may be affected by excavation; special excavation shoring designs; and other measures designed to avoid or minimize the potential adverse effects of settlement. The geotechnical design of the excavations (cut-and-cover and mined tunnels) would consider site preparation and excavation and support using concrete diaphragm walls, or similar technology (refer to Section 1 for discussion of construction excavation and support methods) designed to minimize potential construction related settlements resulting from unstable soft sediments.  Potential construction impacts to existing and future structures along the Corridor of the Enhanced EIS/EIR Alignment may expose structures to geologic hazards (settlement).  

Mitigation Measures

Provisions such as concrete diaphragm walls to support the excavation and instrumentation to monitor settlement and deformation would be used to ensure that structures adjacent to tunnel alignments are not affected by adjacent and nearby excavations.  These provisions would be incorporated into the Project design, preliminary and final engineering, and construction specifications for the Project.  However, despite the best efforts of a contractor to minimize ground movements associated with underground construction, surface settlement is a constant concern in urban environments.  To address this concern, tunnel construction methods that minimize ground movement will be used on this Alternative including, structurally stiff shoring systems, Sequential Excavation Method’s (SEM) ground improvement techniques such as compensation grouting and jet grouting and underpinning.  Because SEM advances the tunnel in small increments, the excavation can be supported in a sequential fashion.  With a rigorous geomechanical instrumentation program accompanying SEM, the underground excavation can be closely monitored for movement before settlements propagates to the surface.  If advance settlement trends are observed, grouting or underpinning can be employed to arrest the movement before surface structures are affected. 

Proposed measures for further managing and limiting the expected deformations of the existing BART/Muni Metro subway tunnels include:  (1) rigorous continuous automated monitoring of the distortions and uplift/settlement movements experienced by  the Market Street tunnels as the new tunnel construction approaches and (2) prior placement of compensation grouting pipes between the Market Street tunnels and the new bored tunnels to allow immediate injection of cement grout to replace ground losses caused by the tunneling should the deformations being continuously measured in the BART tunnels exceed pre-established action thresholds.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

This alternative includes installation of subway tunnels and stations and off-street entries and vent shafts on Fourth Street between Townsend and Market Streets and on Stockton Street between Market and Jackson Streets.  South of Townsend Street on Fourth Street, the light rail construction would be at the surface.  Excavation of the tunnel and stations (by TBM, SEM, or cut-and-cover methods) through the developed Downtown area could result in settlement of geologic materials surrounding the tunnel excavation during construction.  Under Alternative 3A, the new bored Central Subway tunnels would pass approximately five to ten feet beneath the BART tunnels resulting in a slight downward deformation of the overlying BART and Muni tunnels.  Tunneling would be done using state-of-the-art pressurized face TBMs that, in combination with proper operation, minimize ground loss and consequent settlement effects.  Proposed construction methods would involve limited dewatering of the cut-and-cover areas to reduce potential settlement of water bearing soil layers (aquifer materials).  Construction-period settlements could cause potential damage to existing building foundations, subsurface utilities, and surface improvements (e.g., sidewalks and roadways). [begin deletion] Tunnel construction could also result in the potential displacement of BART structures. [end deletion]

A geologic profile for the Fourth/Stockton Alignment Option A is presented in Figure 5-15.  Settlement-related construction impacts would be the same as described above for Alternative 2. 

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2, except subway tunnels for Alternative 3A would be constructed using pressurized face TBM tunneling methods.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

This segment includes installation of subway tunnels and stations and off-street entries and vent shafts on Fourth Street between Bryant and Market Streets, and on Stockton Street between Market and Jackson Streets.  South of Bryant Street, on Fourth Street, the light rail construction would be at the surface.  Excavation of the tunnel and stations (by TBM, SEM, or cut-and-cover methods) through the developed Downtown area could result in settlement of geologic materials surrounding the tunnel excavation during construction.  Under Alternative 3B, the new bored Central Subway tunnels would pass approximately five to ten feet beneath the BART tunnels resulting in a slight downward deformation of the overlying BART and Muni tunnels.  Tunneling would be done using state-of-the-art pressurized face TBMs that, in combination with proper operation, minimize ground loss and consequent settlement effects.  Proposed construction methods would involve limited dewatering of the cut-and-cover areas to reduce potential settlement of water bearing soil layers.  Construction-period settlements could cause damage to existing building foundations, subsurface utilities, and surface improvements (e.g., sidewalks and roadways). [begin deletion]   Tunnel construction could also result in the potential displacement of BART structures. [end deletion]

Based on preliminary and subsequent geotechnical investigations of subsurface materials along the Corridor, tunneling would encounter a variety of geologic materials, including artificial fill, dune sand, Bay Mud, undifferentiated Old Bay deposits, dense sand (Colma Sand) and bedrock (refer to Figure 5-16).^{[5], [6]}  Preliminary geotechnical reports prepared for the mined and cut-and-cover tunneling portions of the Project include recommendations for management of potential construction-period settlements.^[7].[8] 

Similar to impacts described for Alternative 2, the construction impacts of the Fourth/Stockton Alignment Option B from settlement along the Corridor may expose structures to geologic hazards.

Mitigation Measures

The mitigation measures would be the same as described for Alternatives 2 and 3A.

6.11 construction impacts and mitigation for Hydrology

6.11.1 flooding

Alternative 2 - Enhanced EIS/EIR Alignment

Based on an evaluation of existing surface elevations (all elevations equal to or greater than 0 feet SFCD), the Enhanced EIS/EIR Alignment would not be expected to be affected by 100-year high tides or tsunami events.  Where construction of the underground guideway and station structures occurs below the water table in permeable soil and/or rock, the subsurface groundwater flow regime in the immediate vicinity of the structures would be altered.  All permanent structural elements would be detailed to achieve an essentially watertight structure that does not require long-term, continued dewatering.  Local groundwater flow patterns would be altered where jet grouting, secant piles, diaphragm walls and other soil improvement and permanent, impermeable shoring elements are left in place.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA) and Option B (Modified LPA)

Construction, Operation and Cumulative impacts would be the same as described for Alternative 2 above.

Mitigation Measures

No mitigation measures are required.

6.11.2 water quality

Alternative 2 - Enhanced EIS/EIR Alignment

The Enhanced EIS/EIR Alignment would include approximately 1.5 miles of tunneling.  Construction of portals, access shafts to the tunnels, stations, and station entrances would require excavation and transportation of an estimated 524,000 cubic yards of soil and dewatering activities.  (See also Section 5.10, Hazardous Materials) These activities would result in exposure of soil to erosion by runoff.  During the construction phase, it is possible for storm water runoff to mobilize sediments toward the Bay or the City’s combined storm and sanitary sewer system.  The accumulation of sediment could result in blockage of flows, potentially resulting in localized ponding or flooding.

Some local dewatering would be conducted during construction of the deep stations and station accesses.  The construction method for the deep excavations would incorporate watertight concrete diaphragm walls with a base slab.  Dewatering would be used locally to control minor leakage through the walls prior to constructing the base slab once the excavation reaches full depth.  For further discussion of the construction excavation and support method, see Chapter 6.2. 

The high water table and permeable soil conditions, along with the existing inflow of groundwater at the Powell Street Station, require special design considerations to address the potential for groundwater at the Union Square Station and the potential for impacting groundwater flows to the Powell Street Station.  Shoring at the Union Square Station will be designed to be watertight so as not to rely on extensive dewatering.  The station structures will be fully waterproofed with membrane systems.  A design requirement stipulating that the Union Square Station construction not alter the existing groundwater in the vicinity of the Powell Street Station will also be adopted.

The potential for chemical releases is present at most construction sites.  Once released, substances such as fuels, oils, paints, and solvents could be transported to nearby surface waterways and/or groundwater in storm water runoff, wash water, and dust control water, potentially reducing the quality of the receiving waters or causing operational difficulty at the wastewater treatment plant.

The Central Subway Corridor is subject to the SF Public Utilities Commission (SFPUC) regulations (Ordinance 19-92, Sections 118 and 123).  These regulations require a  Storm Water Pollution Prevention Plan (SWPPP) to be submitted to the SFPUC, Water Pollution Control Division for review.^[9]  No additional mitigation for control of construction period runoff would be necessary, because the implementation of the SWPPP meet City requirements for control of storm water.

In accordance with San Francisco Ordinance 19-92, Sections 118 and 123, a contractor would prepare and implement a SWPPP.  The SWPPP would include Best Management Practices (BMPs) designed to reduce potential adverse effects on surface water quality and off-site sedimentation throughout the construction phase of the Project.  Specific measures shall be included in the SWPPP to ensure that runoff from the construction sites does not drain directly to the Bay.  The SWPPP would include:

· Construction Storm Water Management Controls.  These controls would include practices to minimize the contact of construction materials, equipment, and maintenance supplies (e.g., fuels, lubricants, paints, solvents, adhesives) with storm water.  The SWPPP would specify properly designed centralized storage areas that would keep these materials out of the rain.  Spill cleanup materials (e.g. rags, absorbent materials, and secondary containment) would be kept at the work site when handling chemicals.

An important component of the storm water quality protection effort is knowledge of the SWPPP by the site supervisors and workers.  To educate on-site personnel and maintain awareness of the importance of storm water quality protection, site supervisors would conduct regular tailgate meetings to discuss pollution prevention.  The frequency of the meetings and required personnel attendance list would be specified in the SWPPP.

The SWPPP would specify a monitoring program to be implemented by the construction site supervisor, and would include both dry and wet weather inspections.  City personnel shall conduct regular inspections to ensure compliance with the SWPPP; an accepted standard procedure.

· Erosion and Sediment Control.  BMPs designed to reduce erosion of exposed soil may include, but are not limited to: soil stabilization controls, watering for dust control, perimeter silt fences, placement of straw wattles, and sediment basins.  The potential for erosion is generally increased if grading is performed during the rainy season as disturbed soil can be exposed to rainfall and storm runoff.  If grading must be conducted during the rainy season, the primary BMPs selected shall focus on erosion control that is keeping sediment in-place.  End-of-pipe sediment control measures (e.g., basins and traps) shall be used only as secondary measures.  Entry and egress from the construction site shall be carefully controlled to minimize off-site tracking of sediment.  Vehicle and equipment washdown facilities shall be designed to be accessible and functional during both dry and wet conditions.  Additional sources of information regarding BMPs are the California Storm Water Municipal and Construction Activity BMP Handbooks.^[10]

Mitigation Measures

No mitigation measures are required.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

The Fourth/Stockton Alignment Option A would include approximately 1.5 miles of tunneling and excavation for stations and access to stations.  Construction of portals, access shafts to the tunnels, stations, and station entrances would require excavation and transportation of an estimated 489,000 cubic yards of soil, and dewatering activities.  These activities would result in exposure of soil to erosion by runoff.  During the construction phase, it is possible for storm water runoff to mobilize sediments toward the Bay or the City’s combined storm and sanitary sewer system.  The accumulation of sediment could result in blockage of flows, potentially resulting in localized ponding or flooding.

Construction impacts would be the same as described above for Alternative 2.  The strategies outlined for controlling groundwater at the Union Square Station would apply to the Union Square/Market Street Station.

Mitigation Measures

No mitigation measures are required.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

The Fourth/Stockton Alignment Option B would include approximately 1.2 miles of tunneling.  Construction of portals, access shafts to the tunnels, stations, and station entrances would require excavation and transportation an estimated 637,000 cubic yards of soil, and dewatering activities.  These activities would result in exposure of soil to erosion by runoff.  During the construction phase, it is possible for storm water runoff to mobilize sediments toward the Bay or the City’s combined storm and sanitary sewer system.  The accumulation of sediment could result in blockage of flows, potentially resulting in localized ponding or flooding.

Construction impacts would be the same as described above for Alternative 2.  The strategies outlined for controlling groundwater at the Union Square Station would apply to the Union Square/Market Street Station.

All Build Alternatives

No substantial amount of water would be recharged into the groundwater during construction.

Mitigation Measures

No mitigation measures are required.

6.12 construction impacts and mitigation for Biological and Wetland Resources

Alternative 2 - Central Subway Enhanced EIS/EIR Alignment

Construction of the Enhanced EIS/EIR Alignment may result in the removal of small existing street trees along Fourth, Third, Stockton Streets along surface segments and at station entrances. 

Mitigation Measures

Any street trees removed or damaged as part of construction would be replaced along the street at a 1:1 ratio.

Alternative 3 - Central Subway Fourth/Stockton Alignment Option A (LPA) and Option B (Modified LPA)

Construction of Fourth/Stockton Alignment Option A could result in the removal of small existing street trees along the surface segment of Fourth Street and at station entries on Fourth and Stockton Streets.  No wetlands would be affected.  During construction of the North Beach Tunnel Variant for removal of the tunnel boring machine at Columbus Avenue and Union Street, adjacent to Washington Square Park, exposure of roots of mature trees could occur.

Mitigation Measures

Any street trees removed or damaged as part of construction would be replaced along the street at a 1:1 ratio.  A certified arborist would be present during construction of the Columbus Avenue TBM retrieval shaft to monitor protection of tree roots during excavation (2-3 weeks).

6.13 construction impacts and mitigation for Hazardous Materials

Alternative 2 – Enhanced EIS/EIR Alignment

Construction activities for this alternative would disturb soils along the alignment in some areas at a depth of up to 80 feet.  See Section 6.1 for details of the construction techniques.

Construction activities for the surface segment of the Central Subway Enhanced EIS/EIR Alignment include excavation of an estimated 524,000 cubic yards of soil for the construction of the surface light rail tracks and associated utility trenches. 

Previous subsurface soil investigations, historic and current land uses, and known fill areas were described in Section 4.10 to assess the quality of subsurface soils that would be disturbed during construction.  The evaluation indicated the potential for hazardous materials to be present in soils that would be excavated during the construction of the surface light rail tracks, utility trenches, maintenance facility, and portions of the subway.  Potential contaminants include metals, volatile organic compounds (VOCs), semi-VOCs including polynuclear aromatic hydrocarbons (PNAs), total petroleum hydrocarbons, and friable asbestos from serpentine fragments.

Construction of the Enhanced EIS/EIR Alignment may expose site workers and the public to soils potentially containing hazardous materials.  Hazardous materials may be present at concentrations that could adversely affect the health of site workers and the public and could possibly render the soils a hazardous waste, once excavated.  Possible routes of exposure to site workers include absorption through exposed skin, inhalation of dust or vapors, and ingestion. The public could be exposed to contaminants through inhalation of dust or vapors generated from excavation activities carried beyond the construction zone.  Ingestion and dermal contact of contaminants could also affect exposure to the public, if access to the construction zone were not restricted.

Excavated soils generated during construction activities would be transported for off-site disposal at landfills.  For Alternative 2, an estimated 35,000 cubic yards of spoils would need disposal at a Class I facility.  Improper handling of contaminated soils could result in an adverse effect to the public and the environment during transportation.  In addition, disposal at a landfill would be an indirect effect of the Central Subway Enhanced EIS/EIR Alignment since the capacity and life of the landfill(s) would be reduced, potentially requiring the need for additional development of disposal facilities within the State in the future.

During excavation activities, site workers may encounter unanticipated subsurface structures containing hazardous materials such as underground pipelines, underground storage tanks (USTs), and buried drums.  The hazardous materials could pose a health and safety hazard to site workers and the public during excavation and/or activities related to the removal of underground structures.  In addition, the environment may also be adversely affected if the hazardous materials were accidentally released.

^{Diesel-powered equipment would likely be used for soil excavation, tunneling, and other construction activities.  This equipment may be serviced and fueled on-site with substances such as lubricants, diesel fuel, antifreeze, motor oils, degreasing agents, and other hazardous materials.  Improper management,} including an accidental chemical release, of these materials could pose a health and safety hazard to workers, the public, and the environment.

Measures to avoid adverse effects caused by the presence of hazardous materials during construction are required by Article 20 of the San Francisco Municipal Code.  Areas on the Bay side of the 1851 high tide line are subject to compliance with Article 20 requirements if more than 50 cubic yards of soil are evacuated (refer to Chapter 4.0, Figure 4-11).

As indicated in Section 4.10, Hazardous Materials, the requirements of Article 20, administered by the San Francisco Department of Public Health, include:

· Preparation of a Site History Report;

· Collection and analysis of soil samples in accordance with an approved work plan;^[11]

· Preparation of a Soils Analysis Report; and

· Preparation of a Site Mitigation Report.

The Site Mitigation Report would include measures to be undertaken during Project construction to protect site workers, the public, and the environment.  The Site Mitigation Report would include:  1) determination of whether hazardous materials in soil are causing, or likely to cause, significant environmental or health and safety risks, and if so, 2) recommended measures to mitigate the significant risks; and 3) certification statement confirming that either no mitigation is required or the mitigation measures identified in the report, when completed, will mitigate the risks to the environment or health and safety.  As a result, compliance with Article 20 would mitigate the potential effect of exposing soils containing hazardous materials to site workers, the public, and the environment to a less-than-significant level for that portion of the study area located within the boundaries of Article 20 and portions of segments within its jurisdiction.

For the segments located outside of Article 20 jurisdiction, implementation of mitigation measures similar to those required by Article 20 would be needed to reduce the potential exposure effects of soils containing hazardous materials to site workers and the public (see Mitigation Measures below).

Groundwater levels in the study area have been reported to range between 1 and 50 feet below ground surface (bgs).  Construction of the Enhanced EIS/EIR Alignment would require excavation below the groundwater level along portions of the alignment.  Shoring and structural lining methods that limit water ingress are proposed throughout the alignment.  As a result, localized dewatering would be needed to lower the groundwater within the excavation areas during construction.  Dewatered groundwater may be disposed either to the San Francisco Bay or the San Francisco Department of Public Works combined sewer system.

Water generated from dewatering activities cannot be discharged directly to the San Francisco Bay without a permit or approval from the Regional Water Quality Control Board (RWQCB).  The RWQCB reviews requests on a case-by-case basis to determine if the discharge is acceptable.  Groundwater quality data would need to be collected and evaluated to determine the potential pollutant loading and impact to the Bay.  Thresholds identified in the San Francisco Bay Basin Water Quality Control Plan may be used to evaluate the water quality data.  It is unlikely that the RWQCB would permit this type of discharge.

Alternatively, if generated water were to be discharged to the City’s combined storm and sanitary sewer system, a Batch Industrial Wastewater Discharge permit would need to be obtained from the San Francisco Public Utilities Commission, Bureau of Environmental Regulation and Management (BERM) prior to discharge.  The permit application must identify the total estimated volume and duration of proposed discharge and contain water quality data representative of the groundwater effluent.  The groundwater quality data would be reviewed to confirm that it would meet the Batch Wastewater Discharge (BWWD) threshold limits.  Threshold limits for direct discharge into the Bay are typically more stringent than the BWWD threshold limits.  For the purposes of this analysis, previously collected groundwater quality data were compared to the BWWD threshold limits.  Section 4.10, Hazardous Materials, provides a discussion of the groundwater quality data collected throughout the Study Area.

Previously collected groundwater quality data indicate the potential for dewatered effluent throughout portions of the alignment to contain elevated metals, VOCs, petroleum hydrocarbons, and oil and grease concentrations.  These contaminants were found at levels greater than the BWWD threshold limits in several areas.  If dewatered discharge were to contain contaminant concentrations exceeding threshold limits, then direct discharge to the combined sewer system would not be allowed.  However, the discharge could be pretreated to reduce contaminant concentrations to acceptable levels; treatment may include gravity separation or filtration to remove sediment in the water, and/or aeration or carbon treatment for removal of volatile compounds.  These specific measures will be included in the dewatering groundwater management protocol.  If the treated water met the threshold limits, then discharge would be allowed into the combined sewer system provided other requirements were satisfied, including adequate sediment control; Section 4.8, Hydrology and Water Quality, discusses sediment control measures.  Compliance with the dewatered groundwater disposal requirements would meet City requirements.

Dewatering during construction could result in preferential groundwater flow toward the alignment; this would be an indirect effect of the Enhanced EIS/EIR Alignment.  As a result, the direction and rate of groundwater flow and corresponding contaminants from areas outside the alignment could migrate toward the alignment, causing an increase in contaminant concentrations in dewatered groundwater.

The health of construction workers and the public who may be exposed to contaminated groundwater during dewatering activities could potentially be affected.  Possible exposure routes to both site workers and the public could include skin absorption and incidental ingestion. 

Mitigation Measures

Subsurface conditions throughout the alignment may vary significantly.  Based on existing soil quality data, historic and current land use, and areas of known fill, hazardous substances could be encountered in soil excavated during construction of the Enhanced EIS/EIR Alignment.

As indicated above, most of the measures needed to mitigate against these effects are required by Article 20 for those portions of the Enhanced EIS/EIR Alignment bayward of the 1851 high tide line.  However, for those portions not subject to Article 20, similar measures would be necessary to mitigate against the identified adverse effects.  The Article 20 requirements are described below, and the items already completed are noted as appropriate:

· [begin deletion] Site History Report [end deletion] .  A series of technical reports have been prepared consistent with the requirement of an Article 20 Site History Report.  Reports were prepared during the period of 1997 through 2006 as modifications were made to the Alignment. [12]^{, [13], [14], [15],} [16]  Past land uses in the Study Area along Columbus Avenue, Stockton Street, and Fourth Street have been densely packed residential, commercial and industrial structures including a large number of shops and factories.  Commercial uses identified include retail shops and hotels.  Industrial uses included machine shops, paint shops, metal shop, auto body and paint shop, blacksmith shop, printing shop, plating works, tin shop, dyeing and cleaning shop, millinery, sheet metal shop, oil and gas facility, lithography, electroplating works, metal and iron works, oil and gas operation, gas and electric company steam plant, furniture varnishing and finishing, drug factory, iron and bronze works, electroplating works, welding shop, printing shop, iron works, insecticide manufacture, plastic products manufacture, and lighting equipment manufacture.

· [begin deletion] Soil Quality Investigation [end deletion] .  The purpose of the soil quality investigation is to: 1) identify potential contaminants which site workers, the public, and the environment could be exposed to during construction; and 2) classify waste stream(s) of excavated soils to ensure proper soil management (i.e., handling and disposal).  As Article 20 also requires the performance of a soil quality investigation, one soil quality investigation shall be conducted for the entire Light Rail Alternative to satisfy the corresponding requirements of Article 20 and this mitigation measure. Investigations would be conducted by qualified environmental professionals and in conformance with State and local guidelines and regulations. 

Before soil quality investigation activities begin, the lead oversight agency for the Project shall be determined.  The agency may be the San Francisco Department of Public Health (DPH), Department of Toxic Substances Control (DTSC), and/or the RWQCB.  Oversight for areas within Article 20 jurisdiction is provided by DPH. DPH may also provide remedial action oversight for the cleanup of waste releases outside the Article 20 jurisdiction, provided that the requisite technical expertise and capabilities are available to supervise the action.  DPH would be required to notify the DTSC and the RWQCB prior to the commencement of the oversight.

For the Alignment segment between King and Jackson Streets, an approved soil and grab groundwater sampling work plan identified the proposed sampling locations and depths, methodology, and laboratory analyses.[17] 

· [begin deletion] Soil Analysis Report [end deletion] .  All field activities, findings, and recommendations would be documented in a soil analysis report.  The soil and groundwater investigation conducted as described in the 2005 approved work plan was summarized in an investigation report prepared consistent with the requirements of Article 20.[18]^,[19]  

· [begin deletion] Site Mitigation Report (SMR) [end deletion] .  Following the completion of the soil investigation activities and preparation of the Soil Analysis Report, an SMR would be prepared and submitted to the oversight agency for approval.  As Article 20 also requires the preparation of a Site Mitigation Report, one report would be prepared for the Central Subway Project.  The contents of the SMR would include the following, which incorporates Article 20 requirements:

[begin deletion] Description of Environmental Conditions [end deletion] - Identification of the contaminants and potential concentrations that may be encountered during construction; determination of whether hazardous materials in soil would cause, or likely cause, environmental or public health and safety adverse effect.

[begin deletion] Health and Safety Plan (HSP) [end deletion] - The City would specify the mechanism that would be needed to ensure the preparation and implementation of a HSP.  The construction HSP would be prepared by a certified industrial hygienist in accordance with Title 8 California Code of Regulations (CCR), Section 5192; the contents would identify potential chemical hazards and exposure assessment; health and safety procedures to be followed to protect site workers/visitors and the general public from exposure to contaminated soils during construction activities; site worker/visitor training requirements (e.g., initial training, pre-entry briefings, respiratory training, tailgate safety meetings); worker medical surveillance; air monitoring; emergency response procedures; site and engineering controls (e.g., wetting down dusty operations); informational program; and decontamination methods.

The HSP would also discuss safe work practices to protect site workers, the public, and the environment from exposure to hazardous materials associated with fueling, operation, and maintenance of the construction equipment.  In addition, regulatory requirements and Best Management Practices as outlined in Section 5.8, Hydrology and Water Quality, would be implemented to protect the environment from the release of hazardous materials to the environment.

[begin deletion] Guidelines for the Management and Disposal of Excavated Soils [end deletion] - Soil management guidelines would include: 1) procedures for proper soil stockpiling and containment; 2) dust control measures to minimize offsite migration of contaminants; 3) additional soil stockpile sample collection and analytical requirements to meet landfill acceptance criteria, if necessary; 4) transportation and disposal options and procedures; 5) federal and/or California hazardous waste generator requirements if the excavated soils were to constitute a federal and/or California hazardous waste; and 6) record keeping. ^{[20], [21]}

[begin deletion] Certification Statement [end deletion] - Article 20 requires that the Certification Statement confirm that either no mitigation is required or the mitigation measures identified in the report, when completed, would mitigate the risks to the environment or human health and safety.

The SMR required in Mitigations would also include the following components to reduce the effects from exposure to unanticipated subsurface structures containing hazardous materials:   

– Pre-excavation procedures to identify subsurface utility lines and hazardous materials-containing pipelines; this can be accomplished by notifying Underground Service Alert (USA) 72 hours in advance and performing subsurface surveys (i.e., geophysical) when warranted.

– Protocol in the HSP to protect site workers, the public, and the environment if unanticipated structures containing hazardous materials (e.g., underground tanks, pipelines, drums, or wells) were encountered.  Protocol may include criteria for ceasing work immediately, and procedures for performing air monitoring to determine site conditions, and approaches for assessing the hazardous materials involved (e.g., sampling).

–    Protocol for handling unanticipated structures containing hazardous materials including contractor notification to the City of San Francisco.  Due to the likelihood of USTs present along the light rail alignment, the SMR shall describe UST removal procedures, in accordance with State and local requirements including the  following topics:

· Minimizing fire hazards

· Tank emptying

· Vapor displacement

· Tank rinsing

· Tank removal

· Leak reporting and regulatory notification

· Coordination with the DPH to ensure compliance with State and local requirements.

To mitigate the potential for exposing site workers and the public to dewatered groundwater containing hazardous materials, the measures described below would be implemented.

The City would conduct a groundwater quality investigation at areas where groundwater would be dewatered during construction activities.  The purpose of the investigation would be to: 1) identify potential contaminants in groundwater to which site workers and the public could be exposed; 2) provide for an initial assessment of the quality of dewatered groundwater; and 3) to assess treatment options for the groundwater.  Groundwater sampling for the alignment between King Street and Jackson Street was conducted simultaneously with the soil investigation described above.[22]   All field activities, findings, and recommendations would be documented in a groundwater quality investi­gation report.  The results of the groundwater sampling conducted for the Alignment between King Street and Jackson Street was included in the soil investigation report.[23] 

Following the completion of the investigation activities, the Site Mitigation Report (described above) would also include the following:

· Measures in the HSP to protect site workers and the public from contaminated dewatered groundwater; and

· Dewatered groundwater management protocol.

The City would specify the mechanism that would be needed to ensure the preparation and implementation of the dewatered groundwater management protocol.  The dewatered groundwater management protocol would specify: 1) permit criteria to discharge effluent water into the San Francisco Bay and/or the City combined sewer system, whichever is applicable (e.g., when and how the permit would be obtained); 2) pumping and storage handling specifications established by the permit; 3) treatment methods to reduce contaminant concentrations if warranted; 4) verification sampling of the discharge to ensure compliance with regulatory limits; and 5) dewatering operation procedures (e.g., flow rates, discharge point, timing).  Disposal to the Bay or combined sewer system would be contingent on the effluent water quality and approval of the applicable regulatory agencies (RWQCB or BERM).  If discharge to either system were not allowed, then provisions for other off-site disposal would be specified in the groundwater management protocol.

Implementation of the mitigation measures identified herein would mitigate the potential adverse effect of exposure associated with encountering unforeseen subsurface structures containing hazardous materials. 

Contaminated soils excavated from construction of planned or ongoing projects, in addition to the Enhanced EIS/EIR Alignment, may be disposed of at off-site landfill(s).  As a result, the rate of reaching landfill capacities would increase.  Projected quantities of excavated soil requiring disposal should be provided to the landfill(s).  It would then be the landfill’s responsibility to determine whether the acceptance rates are within the landfill’s projected capacity goals.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Construction activities for the surface segment of the Fourth/Stockton Alignment Option A include soil excavation for the construction of the surface light rail tracks and associated utility trenches.  Utility trenches would be excavated to approximately 8 feet below ground surface (bgs).  The surface light rail tracks would be transitioned into a subway tunnel at the portal location.  A cut-and-cover method would be used for constructing the Moscone and Union Square/Market Street stations and to connect the surface tracks to the subway from the portal to Harrison Street.  The remaining portions of the subway would be constructed using a TBM feet.  Construction of the portals, stations, and tunnels would require excavation, transportation, and off-site disposal of approximately 489,000 cubic yards of soil.  For Alternative 3A, an estimated 25,000 cubic yards of spoils would be disposed of at a Class I facility.

Mitigation Measures

Mitigation measures would be the same as described above for Alternative 2, except an additional sampling work plan for the segment along Stockton Street from Jackson Street to Green Street and the portion of Columbus Avenue from Green Street to just north of Union Street would also be prepared for regulatory agency approval as part of the Soil Quality Investigation for North Beach Construction Variant.. 

The additional investigation for the Soils Analysis Report, to be conducted north of Jackson Street and onto Columbus Avenue for the North Beach Construction Variant, would meet the corresponding requirements of Article 20 which include: 1) names/addresses of persons and certified laboratory that conducted the soil sampling, laboratory analysis, and report preparation; 2) explanation of sampling and testing methodology; 3) analytical results; 4) indication of the presence of hazardous materials based on the analyses performed; 5) state and federal agencies to which the presence of hazardous materials has been reported and the date of the report; 6) statement indicating whether the site is listed on the National Priorities List of hazardous waste sites, published by US EPA, or listed as a hazardous substance release site.  In addition to the Article 20 requirements, the report would include the evaluation and results of the waste stream(s) classification of excavated soils.

For the additional investigation to be conducted north of Jackson Street and onto Columbus Avenue, the groundwater investigation will be conducted simultaneously with the soil investigation.  Groundwater quality investigation activities would be performed in accordance with a groundwater sampling work plan approved by the oversight regulatory agency.  The work plan would identify the pro­posed sampling locations, methodology, and laboratory analyses.  Activities would be conducted by quali­fied environmental professionals and in conformance with State and local guidelines and regulations.  Sampling locations would focus on areas subject to dewatering.  Contaminants selected for analysis would be based on existing groundwater quality data collected in the vicinity, land use history, and discharge requirements.

Alternative 3 - Fourth/Stockton Alignment Option B (Modified LPA)

Construction activities for the surface segment of the Fourth/Stockton Alignment Option B include soil excavation for the construction of the surface light rail tracks and associated utility trenches.  Utility trenches would be excavated to approximately 8 feet below ground surface.  The surface light rail tracks would be transitioned into a subway tunnel at the portal locations.  A cut-and-cover method would be used for constructing the Moscone and Union Square/Market Street stations and to connect the surface tracks to the subway.  The remaining portions of the subway would be constructed using two TBMs.  Construction of access portal and subway stations to the tunnels would require excavation, transportation, and off-site disposal of about 637,000 cubic yards of soil.  For Alternative 3B, an estimated 13,000 cubic yards of spoils would be disposed of at a Class I facility.

Mitigation Measures

The mitigation measures would be the same as described above for Alternative 3A.

6.14 construction impacts and mitigation for Air Quality

Since publication of the 1998 EIS/EIR, approaches and analysis tools for evaluating the construction impacts of air quality have changed.  Construction emissions vary substantially from day-to-day, depending on the level of activity, the specific type of construction operations and the prevailing weather in the case of dust emissions.  The BAAQMD does not recommend quantification of construction emissions.  As a result, attempts were not made in this document to estimate construction emissions.  Rather the discussion is based on feasible control measures that are being incorporated into the Project. 

Sensitive receptors susceptible to air quality impacts during construction include:  playgrounds, parks, schools, hospitals, clinics, and health centers, community centers, convalescence homes, and residential areas (refer to Section 4.11.7 for more detailed discussion of sensitive receptors).  School playgrounds and parks along the Project Corridor are shown on Figure 4-4.  Sensitive receptors of particular interest for air quality include:  Yerba Buena Center of the Arts at Third and Mission Streets; Union Square along Stockton Street; Gordon Lau Elementary School playground at Washington Street; Willie “Woo Woo” Wong Playground at Sacramento Street; and Washington Square at Columbus Avenue and Union Street.

Alternative 2 - Enhanced EIS/EIR Alignment

Construction of the guideway would occur by several construction methods, including mining, a sequential excavation method (SEM), a special excavation method (SXM), and cut-and-cover methods.  The Union Square, Market Street, and Moscone stations would be constructed by cut-and-cover.  The Chinatown Station would be mined using the SEM method.  For more construction details, see Section 6.1.

Dust Emissions.  Construction activities involving  soil movement, such as cut-and-cover and to a lesser extent SXM, utility relocation/installation, hauling of spoils could generate dust.  These activities would occur over an estimated period of almost six years and would occur over a surface area of about eight acres.  This area includes construction of the stations, portals, guideway, and utility relocation/installation.  Spoil material from tunnel excavation would be moist and would likely not generate fugitive dust. 

The impacts from construction activities on nearby residences and other areas where the public has access would depend on the proximity of construction work to these areas.  The highest pollutant levels are typically within 200 feet of the construction activity.  Since the location of construction would change, some members of the public may experience occasional annoyances when construction activities are closest to them.  The application of construction-specific control measures would eliminate many potential annoyances.

The following dust control measures as required by the BAAQMD have been incorporated into the Project: [24]

· Where appropriate, active construction areas shall be watered at least twice daily.

· All trucks hauling soil, sand, and other loose materials shall be covered with tarpaulins or other effective covers.

· All unpaved access roads, parking areas, and staging areas at the construction site shall be paved; otherwise, water or non-toxic soil stabilizers shall be applied.  In addition, paved access roads, parking areas, and staging areas shall be swept daily with a water sweeper.  Streets shall be swept daily with a water sweeper in areas where visible soil material is carried onto adjacent public streets.

· Inactive construction areas, including previously graded areas inactive for at least ten days, shall be hydroseeded or applied with a non-toxic soil stabilizers.

· Exposed stockpiles shall be enclosed, covered, and watered twice daily (or applied with a non-toxic soil binder) if material is dry.

· The speed of all vehicles driving on unpaved roads shall be limited to 15 mph.

· To prevent silt runoff to public roadways, sandbags or other erosion control measures shall be implemented.

· Disturbed areas shall be replanted with vegetation as quickly as possible.

· Excavation and grading activities shall be terminated when winds exceed 25 mph.

Controlling dust and PM₁₀ would also reduce PM_2.5 at construction sites.  Air monitoring at playgrounds and school yards would be included as part of the Project.

Exhaust Emissions.  Short-term exhaust emissions would be generated from surface construction-related equipment.  In addition, exhaust emissions would be generated from off-site transport of soils excavated from surface construction, cut and cover, and tunneling activities.  Soils generated from tunneling activities would be transported underground via rail or conveyor belt to the portal locations.  At this point, the excavated soils would be transported off-site.  In addition, construction-related lane closures and detours could cause traffic congestion and as a result additional air pollutant emissions.  See Chapter 3.0 for measures proposed to reduce traffic congestion in the construction area.  Increased emissions would affect short-term air quality and could affect nearby sensitive receptors.  However, the emissions are not expected to cause or contribute to violations of ambient air quality standards.

Implementation of the following control measures will be included in the Project construction specifications and contract documents to further reduce exhaust emissions (including PM_2.5) from construction-related equipment:

· The idling time of all construction equipment used at the site shall not exceed five minutes per hour.

· The hours of operation of heavy duty equipment and/or the amount of equipment in use shall be limited.

· [begin deletion] The idling time of all construction equipment used at the site shall not exceed five minutes per hour [end deletion] .  All equipment shall be properly tuned and maintained in accordance with the manufacturer’s specifications [begin deletion] to perform at EPA certification levels [end deletion] at the manufacturer’s recommended frequency.  [begin deletion] Employ periodic, unscheduled inspections to limit unnecessary idling. [end deletion]

· Prohibit any tampering with engines and require continuing adherence to manufacturer’s recommendations for operations.

· Particulate matter filters shall be installed on all on-site diesel powered equipment for the duration of the Project.

· When feasible, alternative fueled or electrical construction equipment shall be used at the Project site.

· Use ultra-low sulfur fuel if available and maintain receipts from all purchases for verification.

· The minimum practical engine size for construction equipment shall be used.

· Gasoline-powered equipment shall be equipped with catalytic converters, where feasible.

· Use no more than two pieces of equipment simultaneously near or upwind of sensitive receptors.

· Establish emission limits within 1,000 feet of K-12 schools along the Corridor and notify schools of construction activity.

· Develop a plan for limiting truck traffic movements during critical hours to minimize community risk.

· A Contract Project Manager will conduct spot checks for compliance with committed measures.

· [begin deletion] “Reduce use, trips, unnecessary idling from heavy equipment. [end deletion]

· [begin deletion] Use EPA-registered particulate traps and other appropriate controls where suitable to reduce emissions of diesel particulate matter at construction sites. [end deletion]

· [begin deletion] When hauling material and operating non-earthmoving equipment onsite, prevent spillage and limit speeds to 15 mph.  Limit speed of earthmoving equipment to 10 mph.” [end deletion]

An increase in Project-related short-term construction emissions in addition to emissions from other Projects in the Bay Area may result in cumulative effects to air quality for the Enhanced EIS/EIR

Alignment.  However, construction activities are subject to control measures established by BAAQMD to reduce impacts from the Project. 

Mitigation Measures

No mitigation measures would be required.

Alternative 3 – Central Subway Fourth/Stockton Alignment A (LPA)

Construction of the guideway would occur by TBM and decked cut-and-cover methods.  The Union Square/Market Street Station would be constructed by both cut-and-cover and Sequential Excavation Method (SEM).  The Moscone Station would be constructed by cut-and-cover.  The Chinatown Station would be mined using the SEM method.  For more construction details, see Section 6.1. 

Dust Emissions.  Dust impacts would be the same as those described for Alternative 2 with a few exceptions.  It is expected that use of the TBM would help reduce dust emissions during construction of the tunnel.  Construction activities would occur over an estimated period of approximately six years and would occur over a surface area of about five acres, which results in less surface area exposed. 

Impacts should be similar if the North Beach Construction Variant is chosen.  This option would have a TBM retrieval shaft on Columbus Avenue next to Washington Square Park.  However, the exposed area is relatively small and control measures are being included in the Project to reduce dust emissions.

The same dust control measures listed under Alternative 2 would be incorporated into the Fourth/Stockton Alignment Option A.  The application of these dust control measures would eliminate annoyances.

Exhaust Emissions.  The impacts and control measures related to exhaust emission for the Fourth/Stockton Alignment Option A would be the same as those identified under Alternative 2. 

Mitigation Measures

No mitigation measures would be required.

Alternative 3 - Central Subway Fourth/Stockton Alignment B (Modified LPA)

Construction impacts of the Fourth/Stockton Alignment B would be the same as those described for Alternative 3A.  The Union Square/Market Street and Moscone Stations would be constructed using a decked cut-and-cover approach.  The Chinatown Station would be mined using the SEM method.  For more details, see Section 6.2.

Dust Emissions.  Dust impacts and control measures would be the same as those described for Alternative 3A except as noted here.  Construction would occur over an estimated period of approximately 5.5 years, which is a shorter construction period than other alternatives, and would occur over a surface area of about five acres. 

Exhaust Emissions. The impacts and control measures related to exhaust emission for the Fourth/Stockton Alignment Option B would be the same as those identified under Alternative 2. 

Mitigation Measures

No mitigation measures would be required.

6.15 construction impacts and mitigation for Noise and Vibration

Alternative 2 – Enhanced EIS/EIR Alignment

Noise.  Noise impacts from construction would differ for the at-grade and the underground section of the Project.  At-grade construction noise would be generated by heavy equipment used during major construction periods as close as 25 feet to existing structures along the alignment.  Table 6-3 shows the estimated maximum noise levels for the different stages of at-grade construction at 100 feet from a receiver.

Most of the underground tunnel activities would not be audible at street level.  Support equipment for the excavation and tunneling would be located at street level and could include ventilation fans, compressors, electric generator sets and a concrete batch plant.  Construction of the stations would include equipment

TABLE 6-3

ESTIMATED PEAK HOUR CONSTRUCTION NOISE LEVELS

Source: Transit Noise and Vibration Impact Assessment, FTA, May 2006.

at street level such as a crane, excavator, loader, and haul trucks.  Construction activities at each of the stations could potentially affect nearby noise sensitive receivers.  Tunnel excavation material would be removed and stock-piled at the tunnel construction shaft on Fourth Street.  Haul trucks, used to remove the excavated material, would be a potential source of noise along city streets.  Haul routes would have to be selected to avoid impacting residential areas, schools and playgrounds.

Vibration.  As with noise, the vibration from construction is temporary, and, as long as the vibration does not cause any damage to buildings, there would be no permanent impacts.  The vibration processes that are likely to be either intrusive or have the potential for damaging buildings include:  pile driving, demolition with jack hammers and hoe rams, and the use of tracked vehicles close to buildings.  Potential for impact from construction vibration is controlled by adhering to vibration limits for settlement of structures and requiring monitoring to assure that vibration is within specified limits during construction activities.  These types of measures will be included in the construction specifications for this Project and there should not be any vibration-induced damage to buildings during construction and intrusive vibration should not last for more than a few days.

Common vibration producing equipment used during at-grade construction activities include pile drivers, jackhammers, pavement breakers, hoe rams, augur drills, bulldozers and backhoes.  No pile driving is expected during construction of this Project.  Pavement breaking and soil compaction would probably be the activities that produce the highest level of vibration.  Table 6-4 presents various types of construction equipment measured under a wide variety of construction activities with an average of source levels reported in terms of velocity levels.  Although the table gives one level for each piece of equipment, it should be noted that there is a considerable variation in reported ground vibration levels from construction activities based on soil conditions.  The data provides a reasonable estimate for a wide range of soil conditions.

Table 6-4

Vibration Source Levels for Construction Equipment

Lv = RMS velocity in decibels (VdB) re 1 micro-inch/sec

Source: Transit Noise and Vibration Impact Assessment, FTA, May 2006.

Equipment used for underground construction, such as TBM and mine trains would generate vibration levels that could result in audible ground-borne noise levels in residential buildings at the surface.  The operation of the mine trains would be the major source of underground construction vibration since it would operate continuously during the excavation, mining and finishing of the tunnel.  Since underground construction is expected to occur continuously over a 24-hour day, there is the potential for these operations, particularly the mine trains, to be perceptible during the nighttime sleep hours when background noise levels inside the residential buildings are very low. 

Recent transit tunneling projects, such as the Metro Red Line Project in Los Angeles, used a driven-shield TBM for the mining work.  A ground vibration study of the mining operations was conducted to estimate construction vibration both from actual excavation of the tunnel and from the trains used to haul mine spoils out of the tunnel.  The primary conclusions of that study are:

· Vibration from the tunnel excavation would rarely be a significant problem in adjacent communities, although the vibration can be sufficient to cause several hours of intrusive low level ground-borne vibration at residential buildings above the tunnel.

· Although well below any damage thresholds, vibration from mine trains has the potential of causing intrusive ground‑borne noise inside buildings above the tunnel.

Similar effects from the mining operations for this Project would be expected.

Mitigation Measures

Noise and vibration mitigation during construction will require improvement measures to meet the San Francisco Noise Ordinance Limits.  In addition, all construction activities within 200 feet of a historic building or cultural resource structure will have to meet the vibration limits and monitoring requirements presented in Section 4.12 Noise and Vibration Affected Environment.  The final determination of construction noise and vibration impacts will depend on the equipment and activities used by the Contractor to construct the proposed Central Subway Project.  During final engineering design for the LPA, a more detailed construction noise and vibration analysis will be prepared to assess potential impacts to receivers at construction staging areas, tunnel portals, cut-and-cover station construction, and those within close proximity to the underground mining and excavation operations.  Since this information on means and methods of construction is not available now, noise control measures are presented as typical control measures which have been used on other similar construction Projects.  The Contractor for this Project would be responsible for hiring an acoustical consultant to prepare a Noise and Vibration Control Plan that would identify all potential impacts that may occur during construction and would provide adequate control measures to clearly demonstrate that the noise and vibration criteria and limits presented in this SEIR/SEIS would be achieved. 

Noise control measures for construction noise would include the following:

· Use noise control devices, such as equipment mufflers, enclosures, and barriers.  Natural and artificial barriers such as ground elevation changes and existing buildings can shield construction noise.  Stage construction operations as far from noise sensitive uses as possible;

· Avoid residential areas when planning haul truck routes;

· Maintain all sound-reducing devices and restrictions throughout the construction period;

· Replace noisy equipment with quieter equipment (for example, a vibratory pile driver instead of a conventional pile driver and rubber-tired equipment rather than track equipment); and

· Change the timing and/or sequence of the noisiest construction operations to avoid sensitive times of the day.

· Hire or retain the services of an Acoustical Engineer to be responsible for preparing and overseeing the implementation of the Noise Control and Monitoring Plans.

· Prepare a Noise Control Plan that includes an inventory of construction equipment used during daytime and nighttime hours, estimate of Projected construction noise levels, and locations and types of noise abatement measures that may be required to meet the specified noise limits.

· In the case of nighttime construction, the Contractor will comply with the provisions of the nighttime noise variance issued by the San Francisco Police Department.

· Conduct periodic noise measurement in accordance with an approved Noise Monitoring Plan, specifying monitoring locations, equipment, procedures, and schedule of measurements and reporting methods to be used. 

· During nighttime hours, use equipment at the surface of the construction site that, operating under full load, is certified to meet the specified lower noise level limits than standard equipment.

The Contractor would be responsible for the protection of vibration sensitive historic buildings structures that are within 200 feet of any construction activity.  These historic structures have been identified in the Historic Architectural Survey Report (Garcia, 2007).  The maximum peak particle vibration (PPV) velocity level, in any direction, at any of these structures should not exceed 0.12 inches/second for any length of time.  The Contractor would be required to perform periodic vibration monitoring at the closest structure to any construction activities using approved seismographs.  If at any time the construction activity exceeds this level, that activity will immediately be halted until such time as an alternative construction method can be used that would result in lower vibration levels.

Alternative 3 - Fourth/Stockton Alignment Option A (LPA)

Noise and vibration during construction would be similar to the Alternative 2.  The exception would be there is one double-track portal located on Fourth Street between Townsend and Brannan Streets.  The

portal construction on Third Street as part of the Enhanced EIS/EIR Alignment would be eliminated.  Potential impacts under this alternative would be limited to those buildings along Fourth Street.

Mitigation Measures

The mitigation measures would be the same as those identified for Alternative 2.

Alternative 3 – Fourth/Stockton Alignment Option B (Modified LPA)

Noise and vibration during construction would be similar to Alternative 2 except at the double-track portal located on Fourth Street between Bryant and Harrison Streets.  The portal construction on Third Street as part of Alternative 2 would be eliminated.  Potential impacts under this alternative would be limited to those buildings along Fourth Street from Bryant Street south.

Mitigation Measures

The mitigation measures would be the same as those identified for Alternative 2.

[1]     Dames & Moore, Special Excavation Methods for Central Subway, August 20, 1997.

[2]     Geomatrix Consultants, Inc. Geotechnical Data Report and Geologic Profile, Geotechnical Investigations Phase 1A, Rev 1, 27 February  2004

^[3]     Haley and Aldrich, Inc. Final Report on Central Subway Mined Tunnels/Stations for the Muni Third Street Light Rail Project, San Francisco, California, February, 1997.

^[4]     Dames & Moore.  Geotechnical Engineering Recommendations, Central Subway Cut-and-Cover Construction for the Third Street Light Rail Project, 12 March  1997.

[5]     Geomatrix Consultants, Inc. Addendum to Geotechnical Data Report and Geologic Profile for the Fourth/Stockton Alignment, Geotechnical Investigations, Rev 0, 30 March 2005.

[6]     Geomatrix Consultants, Inc. Geotechnical Data Report and Geologic Profile for the Fourth/Stockton Alignment, Geotechnical Investigations, Phase 1B, Rev 0. 1 May 2006.

^[7]     PB/Wong, Working Paper, Recommended Tunnel Construction Methods Study, Rev. 0, March 2004.

^[8]     PB/Wong, Fourth Street Addendum to Effects of NCS Underground Construction on Existing Structures, Rev. 0, March 2005.

^[9]     Franza, Tom.  Water Pollution Control Division, Public Utilities Commission.  Personal communication with BASELINE, July 15, 1997.

^[10]    California Stormwater Quality Association (CASQA).  Stormwater Best Management Practice Handbooks, 2003.

^[11]   Section 1002 of Article 20 identifies the analytical requirements for the soil samples.

[12]   No. 96.218E, Hazardous Materials Technical Report, Baseline Environmental Consulting, June, 1997.

[13]   Phase I Environmental Site Assessment and Site History Report, Central Subway Alignment, San Francisco, California, Revision 1, Geomatrix Consultants, Inc., December 18, 2003.

[14]   Addendum to Phase I Environmental Site Assessment and Site History Report, Task 1.02-03, Hazardous Material Investigations, Revision 0, Geomatrix Consultants, Inc., April 1, 2005.

[15]   Phase II Hazardous Materials Investigation Report, for the Fourth/Stockton Alignment, Task 1.02-03, Hazardous Material Investigations, Revision 0, Geomatrix Consultants, Inc., May 18, 2006.

[16]   Addendum No. 2 to Phase I Environmental Site Assessment and Site History Report, Task 1.02-03, Hazardous Material Investigations, Revision 0b, Geomatrix Consultants, Inc., February 9, 2007.

[17]   Phase II Work Plan, Task 1.02-03, Hazardous Materials Investigation, Revision 0, Geomatrix Consultants, Inc., July 20, 2005.

[18]   Phase II Hazardous Materials Investigation Report, for the Fourth/Stockton Alignment, Task 1.02-03, Hazardous Material Investigations, Revision 0, Geomatrix Consultants, Inc., May 18, 2006.

[19]   Ibid.

^[20]   Disposal options for the excavated soils would be dependent on the results of waste stream classification.  Nonhazardous wastes must be disposed at a Class II or III landfill facilities; federal (i.e., RCRA) hazardous wastes must be disposed at a Class I landfill facility; non-RCRA California hazardous waste may be disposed of at either a Class I landfill or an out-of-state landfill permitted to accept California hazardous waste.

^[21]   If excavated soils were classified as a federal hazardous waste, then compliance with Title 40 Code of Federal Regulations (CFR) Part 261 would be required.  If excavated soils were to constitute a California hazardous waste, then compliance with Title 22 CCR,  Section 66262 would be required.  These requirements were established to regulate the management of generated hazardous wastes and protect site workers during management of these wastes.

[22]   Phase II Hazardous Materials Investigation Report, for the Fourth/Stockton Alignment, Task 1.02-03, Hazardous Material Investigations, Revision 0, Geomatrix Consultants, Inc., May 18, 2006.

[23]   Ibid.

[24]   Bay Area Air Quality Management District, CEQA Guidelines Assessing the Air Quality Impacts of Projects and Plans, December 1999.