Western/Polson Buildings looking Southwest from the...

214 Chapter 8 – Mitigation

Western/Polson Buildings looking Southwest from the norton Building towards Colman Curve

Alaskan Way Viaduct Replacement Project Final EIS 215

What is in Chapter 8?

This chapter identifies WSDoT’s mitigation commitments as

well as other possible mitigation measures that could be used for

permanent and construction (temporary) project effects.

MITIGATION OVERVIEW

Mitigation commitments are project actions andperformance standards, often established by regulation,that are used to address project effects. To meet thesecommitments, Washington State Department ofTransportation (WSDOT) will implement bestmanagement practices (BMPs) during construction andcarry out specific mitigation measures based on theproject’s effects.

In this chapter, the word “will” is used to describemitigation measures to which WSDOT is committed if abuild alternative is selected. The word “could” generallyprecedes a suite of specific BMPs from which WSDOTcould choose to achieve its mitigation commitments. If amitigation measure is found to be ineffective, WSDOT willdevelop other appropriate mitigation with FHWA’sapproval. If the Viaduct Closed (No Build Alternative) isselected, then the mitigation measures discussed here willnot be implemented.

The project will not result in permanent adverse effects forall of the resources considered in this Final EnvironmentalImpact Statement (EIS). For some resources, the projectwill result in beneficial permanent effects; for others, thereare simply no permanent effects. For the resources withbeneficial or no permanent effects, mitigation is notproposed. Exhibit 8-1 shows the resources for which

mitigation is proposed and for what type of effect(permanent and/or construction). If mitigation is notproposed for a resource, it is not discussed in this chapter.

Mitigation Commitment TrackingWSDOT has an established department-wide program that identifies and manages commitments, includingenvironmental mitigation measures. Projects assign aCommitment Lead who reviews project commitmentdocuments, such as interagency agreements, requests forproposals, environmental documents, permits, and agencydirectives and concurrence letters. From these documents,

Exhibit 8-1mitigation for Permanent and Construction effects

resource Permanent effects Construction effects

Transportation X X

Noise No mitigation proposed X

Vibration No mitigation proposed X

Views X X

Land use No mitigation proposed X

Economics No mitigation proposed X

Parking No mitigation proposed X

Historic Resources X X

Archaeological Resources No mitigation proposed X

Parks, Recreation, and open Space

No mitigation proposed X

Neighborhoods and Community Resources

X X

Minorities and Low-Income Populations

X X

Public Services No mitigation proposed X

utilities No mitigation proposed X

Air Quality No mitigation proposed X

Energy and Greenhouse Gas Emissions

X X

Water Resources No mitigation proposed X

Fish, Aquatic, and WildlifeSpecies and Habitat

X X

Soils and Groundwater X X

Hazardous Materials X X

Note: No mitigation is proposed for resources that are

not permanently affected or have a beneficial

permanent effect.

the Commitment Lead develops an inventory ofcommitments that are entered into an electronicCommitment Tracking System (CTS). The CTS allows theCommitment Lead to assign staff to commitments and toidentify existing guidance documents that help themsuccessfully comply with the commitment. Commitmentsthat require monitoring are noted in this chapter, asappropriate.

The CTS also facilitates developing the contract duringthe Plans, Specifications, and Estimates process. It alsoallows the Design and Construction offices to manage thestatus of their commitments. The CTS providescompliance recording and reporting features that areconsistent with existing program policy and permitrequirements. Updating and tracking commitment statusfrom project design to construction and closeout iscoordinated via team meetings. Regular updates to theCTS are made in order to generate current commitmentstatus reporting, reviewed during meetings by project andprogram management.

MITIGATION FOR PERMANENT EFFECTS

Proposed mitigation for the tolled and non-tolled buildalternatives would be the same for elements of theenvironment discussed below, except as indicated fortransportation and minority and low-income populations.

1 What mitigation is proposed for permanenttransportation effects?

Permanent transportation mitigation measures are notproposed for the build alternatives without tolls becausethere are no permanent adverse effects on thetransportation network.

CHAPTER 8 - MITIGATION


As discussed in Chapter 5, if the build alternatives aretolled, some traffic is expected to divert from SR 99 toavoid paying a toll. This diverted traffic would affect traffic,including freight and transit, on downtown surface streetsas well as the SR 99 mainline due to queues exceeding off-ramp capacity. However, the transportation networkwould operate more effectively even with the divertedtraffic than it would under the Viaduct Closed (No BuildAlternative).

Nevertheless, WSDOT has acknowledged that anacceptable long-term tolling solution should be sought tominimize the amount of diverted traffic in order to optimize operation of the transportation network for allusers. Strategies for optimization will be developed by theTolling Advisory Committee (TAC), which will beestablished by WSDOT, as outlined in section 2.12 ofMemorandum of Agreement GCA 6486. When the TACcompletes the first phase of its work in 2012 and in furtherphases, WSDOT and the City will jointly review therecommendations developed by the TAC. Forimprovements on state facilities or requiring state funding,WSDOT will recommend strategies developed by the TAC(or other strategies as appropriate) to the StateTransportation Commission and seek funding for suchstrategies. WSDOT will work with the State, City, Port ofSeattle, and King County in order to implement TACstrategies or other tolling mitigation strategies. Subject tolegislative appropriation, WSDOT will fundrecommendations agreed to by WSDOT and the City. Ifneeded, additional environmental analysis may beperformed to evaluate the potential effects of proposedstrategies before implementation. The TAC is expected torefine its analysis and recommendations through 2015when toll implementation is expected to begin. The TACwill continue its work for up to one year after tollingbegins to review the effects of the implemented tolling anddiversion minimization strategies and to make furtherrecommendations, if necessary.

Potential Strategies to Reduce Traffic Diversion • Refine the tolling strategy; this may include

modifying toll rates and times that tolls would be

charged as well as implementing regional tollingand/or tolls on other facilities.

• Reduce the level of toll revenue needed (andthereby lower the toll rate needed) by identifyingalternative funding sources consistent with fundingagreements among the parties.

Potential Strategies to Manage Diverted Traffic• Set priorities for street use by time of day for

various users (cars, trucks, bicycles, pedestrians,transit, parking) consistent with the City’s CompleteStreets policy goals

• Identify opportunities for traffic calming and other restrictions on certain modes of travel

• Create “transit first” policies through transit priority streets and other methods to improve transit speed and reliability

• Use other traffic demand management measures

• Fund enhanced transit services and vanpools

2 What mitigation is proposed for permanent effects on views?

Bored Tunnel AlternativeIn addition to the mitigation inherent with this alternative(construction of a bored tunnel avoids the visual effect ofan above-grade or at-grade transportation facility),WSDOT has developed architectural (tunnel operationsbuildings) and portal design guidelines for the project tocreate a consistent visual palette and to match thecharacter of the surrounding streetscape. The guidelinesare appropriate for the urban environment in the projectarea and apply to the tunnel portals, ramps, connectionsto the urban street system, city streets, sidewalks, bicycleand pedestrian trails, and the urban landscape.

The design guidelines will include, but are not limited to,the following elements:

• Develop a design theme for structural elements

• Soften the appearance of roadway areas by usinglandscape materials and street trees and placingtrees where they do not block view corridors

• Provide lighting that meets functional requirementsand enhances the scenic qualities and night-timeexperience of the city

• Enhance intuitive wayfinding and a sense oforientation and destination

• Complement the context and qualities of adjacentneighborhoods with an appropriate scale, massing,and character of the structures

The Seattle Design Commission will review the designfeatures of buildings and above-grade elements to beincorporated into the design for the project.

Cut-and-Cover Tunnel AlternativePotential mitigation measures would be the same asdescribed above for the Bored Tunnel Alternative.

Elevated Structure AlternativePotential mitigation measures would be the same asdescribed above for the Bored Tunnel Alternative, exceptfor the measures related to the tunnel operationsbuildings at the south and north portals.

WSDOT would likely receive input from the Seattle Design Commission on architectural features that could beincorporated into the concrete columns, retaining walls,and other features to enhance the visual quality of thisalternative.

3 What mitigation is proposed for permanent effects onhistoric resources?

Bored Tunnel AlternativeWSDOT, FHWA, the State Historic Preservation Officer,the City Preservation Officer, and affected tribes have

What is the tolling Advisory Committee?

The Tolling Advisory Committee (TAC) has 15 members who are

appointed by the Mayor of Seattle, Seattle City Council, and

WSDOT. The purpose of the TAC is to make advisory

recommendations to the project lead agencies, Governor,

Legislature, Transportation Commission, Seattle City Council, and

Seattle Mayor on strategies for:

• Tolling

• Minimizing traffic diversion due to tolling

• Mitigating traffic diversion effects on city streets and I-5.

The TAC was established by City of Seattle Ordinance 123542,

passed February 7, 2011

(http://clerk.ci.seattle.wa.us/~archives/Ordinances/Ord_123542.pdf).


completed a Memorandum of Agreement for the S. Holgate Street to S. King Street Viaduct ReplacementProject that addresses mitigation for demolishing theviaduct and decommissioning the Battery Street Tunnel.Decommissioning the Battery Street Tunnel was includedin the Memorandum of Agreement because it and theAlaskan Way Viaduct are considered one historic resource.Under that Memorandum of Agreement, implementationof mitigation measures is ongoing and includescommitments, such as a podcast and an interactive websiteabout the history of the Alaskan Way Viaduct.

WSDOT also has completed and submitted a HistoricAmerican Engineering Record (HAER) report to theNational Park Service.¹ The HAER includes photographsand narrative essays of the viaduct and Battery StreetTunnel.

WSDOT has outlined mitigation for adverse constructioneffects on other historic resources in a Memorandum ofAgreement, which is discussed in Question 17 of thischapter.

Cut-and-Cover Tunnel AlternativeIn addition to the mitigation measures described above for the demolition of the viaduct and decommissioning of the Battery Street Tunnel, WSDOT would mitigate therelocation of the Washington Street Boat Landing pergolathrough restoration and replacement of the pergola at thewater’s edge.

WSDOT would mitigate the Elliott Bay Seawall demolitionthrough (1) HAER documentation of the seawall, and (2) preservation and appropriate replacement of thehistorical plaques and markers along the seawall.

Elevated Structure AlternativeMitigation for effects associated with this alternative wouldbe the same as those discussed above for the Cut-and-Cover Tunnel Alternative.

4 What mitigation is proposed for permanent effects onneighborhoods and community services or resources?

Mitigation Common to All Build AlternativesEach year, WSDOT develops a comprehensive publicoutreach and communications plan, which incorporatesthe use of a variety of communication methods, such aswebsites, community e-mail updates, media relations,public meetings, interviews with social service providers,presentations to neighborhood groups, written materials,and information booths at community events tocommunicate project information and engage agencies,tribes, and the public. In an effort to minimize effectsrelated to changes in travel patterns due to access changes,WSDOT will use these outreach activities to communicatewith the public to help people learn about and adjust tothe new facility. WSDOT will communicate with ownersand operators of community facilities, park and recreationfacilities, religious and cultural institutions, social andemployment services, and government agencies. Theseefforts will occur before the new facility opens.

5 What mitigation is proposed for permanent effects onminorities and low-income people?

Mitigation Common to All Build AlternativesAs part of the public outreach and communications plan,as discussed in Question 4 above, WSDOT willcommunicate news about the new roadway facilities todisadvantaged populations, including low-income people,persons with limited English proficiency, accessibility ormobility disabilities, the elderly, and the transit-dependent.The outreach would use English and, when appropriate,materials would be translated into other languages such asChinese, Spanish, Tagalog, and/or Vietnamese toaccommodate the area’s diverse population.

Other measures WSDOT will implement to help avoid,minimize, and mitigate potential effects on minority andlow-income people are:

• Encourage mass transit agencies to conductoutreach activities to communicate transit

operations to persons who are low income anddependent on transit.

• Work with citizen participatory groups and serviceproviders, such as committees, task forces, advisorybodies, housing authorities and social services tocommunicate and assist disadvantaged populationswith transportation options.

• Work with homeless service providers,neighborhood groups, the City, and King County toensure the safety and survival of nearby homelesspeople. Nearby homeless people include those livingoutdoors or in vehicles located under or neartransportation facilities within the project area.

Measures Specific to the Tolled Build AlternativesTolling the build alternatives would not result indisproportionately high and adverse impacts to low-income or minority populations. However, WSDOTwill employ the following measures to reduce theinconvenience of tolling, such as the requirement topurchase transponders, for low-income and minoritypopulations:

• Establish customer service center storefronts in thetravelshed. Find locations online at:http://www.wsdot.wa.gov/goodtogo/contacts.htm.

• Provide public service announcements in multiplelanguages, such as Chinese, Spanish, Tagalog,and/or Vietnamese, regarding the Good To Go!™accounts and transponders.

• Sell Good To Go!™ transponders at convenientlocations, such as grocery stores, convenience stores,or pharmacies throughout the travelshed andconvenient to lower-income neighborhoods.

• Share information with and through other publicservice providers.

1 Sheridan 2009.


• Promote rideshare opportunities such as those inRideshareonline.com, carpoolworld.com,commuteseattle.com, and vanpool providers.

• Enable people without credit cards or checkingaccounts to obtain transponders by paying with cashor Electronic Benefit Transfer (Quest) cards issuedby the Washington State Department of Social andHealth Services.

• Provide social service agencies with tollinginformation and options to avoid the tolls.

The mitigation proposed in Question 1 would also benefitlow-income drivers. These mitigation measures wouldresult in improved traffic operation on SR 99, lessdiversion to city streets, and better management ofdiverted traffic. These measures are expected to improvetravel times on alternate routes (streets other than SR 99)that low-income drivers likely would use if they choose notto pay the toll. This work will be evaluated by the TollingAdvisory Committee and may be the subject ofrecommendations by that body.

6 What is proposed to minimize long-term energyconsumption?

Mitigation Common to All Build AlternativesMeasures that WSDOT will implement to reduceoperational energy consumption (reduced fuel orelectricity use) include, but are not limited to, thefollowing:

• Encourage use of carpools and transit to reducevehicle miles of travel on roadways in accordancewith Washington State’s Commute Trip ReductionEfficiency Act and WSDOT’s Commute TripReduction Program. The expected results of the Act and Program are fewer vehicle trips traveled,reduction in greenhouse gas emissions, and energysavings through use of less fuel.

• Build energy-efficient tunnel operations buildings.The buildings will be designed to LEED Silverstandards, though certification may be unattainabledue to current LEED definitions.

• Use energy-efficient ventilation equipment, lighting, signals, and signage.

• Use variable-message signs to help drivers avoidcongested areas to reduce slow moving traffic andidling, which leads to extra fuel consumption.WSDOT will determine sign locations by usingexisting condition traffic counts in conjunction withthe project’s maintenance of traffic (MOT) plan,both of which would identify the congested areas.

7 What mitigation is proposed for permanent effects onfish, aquatic, and wildlife species and habitat?

Bored Tunnel AlternativeThere are no proposed mitigation or habitatenhancement measures for the Bored Tunnel Alternativebecause there are no permanent effects on fish, aquatic,and wildlife species and habitat. The seawall would not bereplaced with this alternative so there would be no aquatichabitat disturbance. This alternative is expected to eitherimprove or maintain the water quality of stormwaterrunoff discharged from the study area by reducing ormaintaining the overall amount of pollutant-generativeimpervious surface and/or discharging more stormwaterto the combined sewer system. Improved water qualitywould be beneficial to fish, aquatic, and wildlife speciesand habitat.

However, the National Marine Fisheries Service (NMFS)Biological Opinion (BO) outlined terms and conditionsrelated to stormwater management to avoid effects. Theyare:

• WSDOT will ensure compliance with the biologicaleffects thresholds for dissolved copper and dissolvedzinc at the established points of compliance inElliott Bay and Lake Union. The thresholds are

2.0 μg/L over ambient levels not exceeding 3.0 μg/L for dissolved copper, and 5.6 μg/L overambient levels between 3.0 μg/L and 13.0 μg/L fordissolved zinc.

• If the final stormwater design differs from the design evaluated in the BO, then WSDOT willevaluate pollutant loadings and concentrations forthat design to determine if they differ significantlyfrom those considered in the consultation. If thepredicted pollutant loadings or concentrationsexceed those addressed in the BO, WSDOT willprovide to NMFS a description of the designchange(s) and a revised stormwater analysis.

• WSDOT will implement the programmatic approach to stormwater monitoring, as outlined inthe “Programmatic Monitoring Approach forHighway Stormwater Runoff in Support ofEndangered Species Act (ESA) Section 7Consultation,” dated June 2009.² WSDOT will notifyNMFS immediately if the results of this programtrigger any of the relevant reinitiation requirements.

Cut-and-Cover Tunnel AlternativeWSDOT will mitigate the effects on fish, aquatic, andwildlife species and habitat that result from thereplacement of the seawall. Specific mitigation and habitatenhancement measures will be identified throughadditional coordination with agencies and tribes, theevaluation of potential project effects, and development ofthe project design.

Elevated Structure AlternativeWSDOT will mitigate the effects on fish, aquatic, andwildlife species and habitat that result from thereplacement of the seawall. The coordination process toidentify specific mitigation measures would be the same asdescribed above for the Cut-and-Cover Tunnel Alternative.

2 FHWA et al. 2009.


8 What mitigation is proposed for permanent effects onsoils and groundwater?

Mitigation Common to All Build AlternativesWSDOT will mitigate for effects on soils. A potential effectis groundwater mounding, which results in raisedgroundwater levels that could lead to flooding in buildingsadjacent to the new facility. Groundwater mounding willbe evaluated for all walls or soil improvement zones thatare longer than 100 feet and may block groundwater flow.If the magnitude of the groundwater mounding is lessthan the current measured natural fluctuation ofgroundwater in the soil, then no mitigation measureswould be necessary because the groundwater moundinglevels would be consistent with existing water table levelsin the study area so there would be no effect. If highermounding is anticipated, WSDOT will implementappropriate mitigation measures into the design of thefacility during final design. Such measures could consist ofproviding a path for groundwater via pipes, or drainagetrenches, through the retaining walls or soil improvementzones to eliminate the potential for an adverse level ofgroundwater mounding.

Bored Tunnel AlternativeIn addition to the mitigation discussed above that wouldapply to all the build alternatives, the tunnel liner would be monitored on a long-term basis to determinewhether openings are developing in the liner segmentsand whether groundwater seepage and soil migration areoccurring through the openings. Maintenance would beperformed as needed based on the monitoring results.

Cut-and-Cover Tunnel AlternativeThe mitigation measures would be those described abovethat are common to all the build alternatives.

Elevated Structure AlternativeThe mitigation measures would be those described abovethat are common to all the build alternatives.

MITIGATION FOR CONSTRUCTION EFFECTS

Proposed mitigation for the tolled and non-tolled buildalternatives would be the same for the elements of theenvironment discussed below.

9 What mitigation is proposed for transportation effectsduring construction?

Mitigation Common to All Build AlternativesWSDOT, King County, and the City have developed andare implementing transportation improvements tominimize traffic effects during construction to keeppeople and goods moving. These measures are designedto increase transit options, shift traffic away fromconstruction areas, and provide drivers with theinformation they need to choose less congested routes.

These improvements, which are all completed except forthe one noted as under construction, include thefollowing:

• Installing and operating variable speed signs andtravel time signs on I-5 to help maximize safety andtraffic flow.

• Providing funding for the SR 519 Phase 2 Project to improve connections from I-5 and I 90 to thewaterfront.

• Providing funding for the S. Spokane Street ViaductWidening Project, which includes building a newFourth Avenue S. off ramp for West Seattlecommuters. This project is under construction.

• Providing funding for increased bus service in theWest Seattle, Ballard/Uptown, and Aurora Avenuecorridors for some of the construction period, aswell as a bus travel time monitoring system.Increased bus service is currently provided for the S. Holgate Street to S. King Street ViaductReplacement Project through 2014. Funding for thisservice may be extended as mitigation for this

project, but funding for this extension has not yetbeen secured.

• Installing new traffic technology on SR 99 and major routes leading to SR 99 to keep people andgoods moving.

• Upgrading traffic signals and driver informationsigns for the Elliott Avenue W./15th Avenue W., West Seattle, and South of Downtown (SODO)corridors to support transit and traffic flow.

• Providing information about travel alternatives and incentives to encourage use oftransit, carpool, and vanpool programs.

In addition, WSDOT will develop localized mitigationmeasures, as construction details are refined. Examples oflocalized measures are:

• Constructing temporary signals, where necessary

• Stationing flaggers at key intersections to facilitatefreight and general-purpose traffic movements andexpedite travel for emergency vehicles

Before construction begins, WSDOT will prepare a trafficmanagement plan, to be approved by the City, to ensurethat construction effects on local streets, property owners,and businesses are minimized. The traffic managementplan will include the following measures:

• Descriptions of traffic phasing to accommodateconstruction staging. The phasing will includeconceptual MOT plans, expected general-purposetraffic restrictions by construction phase androadway, and transportation-mode-specific effectsand mitigation for the effects.

• Descriptions of requirements for temporaryroadways.


• Procedures for identifying and incorporating the needs of transit operators, utility owners, ferry traffic, Port of Seattle traffic, the Seattle Center,and business owners in the project area.

• Procedures for identifying and incorporating theneeds of pedestrian and bicycle flow, including, forexample, mitigation for sidewalk closures andrequirements related to the Americans withDisabilities Act (ADA).

• Procedures for seeking concurrence of stakeholdersand implementing road and lane closures.

• Procedures for identifying and incorporating theneeds of local agencies affected by the work,specifically, but not limited to, the Port of Seattleand access to Terminal 46.

• Processes for signing transitions during constructionfrom one stage to the next, and from interim topermanent signing.

• Procedures for identifying and incorporating theneeds of emergency service providers, firefighters,law enforcement entities, and other related corridorusers, as well as procedures for ensuring that allinformation required by these agencies to protectthe public is made available.

• Provisions for incident and emergency response.

• Processes for identifying, producing, and obtainingacceptance of the designs of temporary trafficsignals.

• Methods and frequency of inspection andmaintenance of all traffic control throughout theproject area.

• Descriptions of contact methods, personnelavailable to make decisions and ensure that issuesare addressed in a timely and appropriate manner,

and response times for any conditions requiringattention and response 24 hours a day.

• Identification of measurable limits for the repairand replacement of traffic control devices, includingtemporary and permanent pavement markings.

• Processes for determining the needs for revisedtraffic signal timings, and if revisions are required,detailing the procedures for the development,review and acceptance, implementation, testing, and maintenance of all affected signals.

• Provisions for maintaining existing access toproperties, whenever possible.

• Provisions for providing continuous access toestablished hazardous material routes, transit routes,and school bus routes.

• Procedures for modifying the plans as needed toadapt to current project circumstances.

• Procedures for incorporating the needs of eventtraffic, including coordination with Seattle Center,Safeco Field, and Qwest Field.

• Procedures for determining detour routes.

• Procedures for communicating MOT informationand issues for the project to public information personnel and the public.

• Procedures for accommodating MOT plans ofadjacent projects, if applicable.

• Procedures for accommodating MOT plans whenthe staging schedule changes for the Alaskan WayViaduct Replacement Project or any adjacentproject.

• Identification of temporary access connectionsbetween facilities.

• Identification of haul routes.

10 What can be done to minimize traffic effects whenmultiple projects are being constructed?

Constructing multiple projects within the same area cancompound transportation effects. Other projects that maybe constructed during the same time as the Alaskan WayViaduct Replacement Project and that would contribute toconcurrent effects on transportation in the study area are:

• Mercer West Project • S. Spokane Street Viaduct Widening Project • S. Holgate Street to S. King Street Viaduct

Replacement Project • Elliott Bay Seawall Project (if the Bored Tunnel

Alternative is selected)

WSDOT and the City communicate regularly regardingconstruction staging and coordination for these projects.Both lead agencies are striving to minimize construction-related disruptions. As mentioned above in Question 9,WSDOT, King County, and the City have developed andare implementing transportation improvements tominimize traffic effects on keep people and goods movingin and through Seattle.

11 What mitigation is proposed for noise effects duringconstruction?

Mitigation Common to All Build AlternativesBecause of the magnitude of the project, WSDOT willobtain Major Public Project Construction Noise Variances,which involves the preparation of a Noise Managementand Mitigation Plan. The noise variances will be obtainedprior to the start of nighttime construction activities. Togrant this type of noise variance, the City requires that thepublic have an opportunity to comment on the proposal.To date, two public meetings have already been held aspart of the application process. WSDOT will implementthe following mitigation measures to comply with the Major Public Project Construction Noise Variances(the variances could include more measures than listed


here) and the project’s Noise Management and Mitigation Plan.

WSDOT will implement measures to minimize nighttimeand weekend construction noise to prevent exceeding the noise variance levels (except in the case of emergency)during these hours: between 10:00 p.m. and 7:00 a.m. onweekdays, or between 10:00 p.m. and 9:00 a.m. on weekends and legal holidays. Measures implemented tominimize construction noise and comply with the noise-level limits established in the Major Public ProjectConstruction Noise Variances are listed below:

• Ensure that all equipment meets the noise limits and is properly maintained and operated.

• Construct noise barrier walls or functionallyequivalent materials at stationary construction sites.The length and height of the noise barrier walls willbe confirmed during final design. WSDOT will confirm the length and height of the noisebarrier walls prior to nighttime construction. Forthe Bored Tunnel Alternative, noise barrier walls areplanned at both portal construction areas. Thelocation(s) and dimensions of the noise barrier wallswill be determined during final design.

• Construct gates and/or doors in noise barrier wallsfor sound containment. Edges of the gates anddoors will overlap the fence to eliminate gaps;during nighttime hours, gates and doors will be keptclosed, except to allow access to the constructionsite; and access doors (or man doors) will beincorporated into the gates to limit the need toopen large gates at night.

• Use broadband or strobe backup warning devices orbackup observers instead of backup warning devicesthat make noise for all equipment, except dumptrucks, in compliance with WashingtonAdministrative Code (WAC) Sections 296-155-610and 296-155-615.

WSDOT will control nighttime construction noise levelsthrough two methods: noise-level limits and noise-controlmeasures. This approach provides the flexibility of eitherprohibiting certain noise-generating activities duringnighttime hours or implementing noise-control measures(e.g., temporary noise barriers, noise curtains, noise tents,or the use of quieter equipment) to meet the noise limits(as outlined in the project’s Noise Management andMitigation Plan). WSDOT will use the following noise-control measures, as appropriate or necessary:

• Use temporary construction site noise barriers (bothstationary and movable).

• Employ noise control curtains.

• Prohibit jack hammering and impact pile drivingduring nighttime hours; impact or impulse toolsused from 5:00 p.m. to 10:00 p.m. would be subjectto a noise-level limit of 5 dBA above the existingnoise level.

• Use two-way radios for communication and prohibitthe use of public address systems during nighttimehours, except for emergency notifications.

• Grade surface irregularities on construction sites toprevent impact noise and ground vibrations frompassing vehicles.

• Use bed liners for trucks performing export haul.The bed liners may consist of but are not limited toaluminum, rubber, sand, or dirt.

• During pavement removal, remove material spilledon the roadway by hand or by sweeping, rather thanscraping, during nighttime hours.

WSDOT will provide up-to-date information onconstruction activities and construction noise to projectarea neighbors and project stakeholders. WSDOT willprovide a 24-hour hotline and project email, and an

answering service to respond to calls during nighttimehours.

12 What mitigation is proposed for vibration effectsduring construction?

Mitigation Specific to the Bored Tunnel AlternativeSpecific mitigation measures to address potential vibrationeffects during tunnel boring activities are outlined in thedesign-builder’s proposal. These measures are discussedbelow. If the Bored Tunnel Alternative is not selected,WSDOT will develop specific vibration mitigationmeasures for the selected alternative.

WSDOT will measure, analyze, and mitigate groundvibration by and continuously gathering comprehensivevibration data during construction.

Before the start of construction, WSDOT will implementthe following measures,:

• Develop a detailed Vibration Mitigation andMonitoring Plan according to WSDOTrequirements.

• Identify and categorize potentially impactedreceptors (building occupants), buildings(especially historic buildings in the Pioneer Squarearea), above ground structures (including theSeattle Monorail), and underground utilities.

• Determine appropriate vibration measurementand/or monitoring locations.

• Perform a baseline ambient vibration survey atselected locations.

• Identify expected sources of vibration duringconstruction activities, including the TBM, muckconveyor system, pile driving, and demolition of theexisting viaduct.


• Estimate ranges of expected vibration levels atpotentially impacted receptors, buildings andunderground utilities.

If determined to be necessary and practical for specificreceptors, WSDOT will implement the followingmitigation measures:

• Develop an empirical site-specific ground vibrationpropagation model to improve accuracy ofpredictions as necessary.

• Perform ground vibration propagation tests atselected locations along tunnel alignment inconjunction with a geotechnical consultant.

• Compare predictions with specified criteria,summarize expected impacts, and recommendvibration mitigation measures where needed.

During construction, WSDOT will implement thefollowing mitigation measures, as necessary:

• Review vibration data according to the VibrationMitigation and Monitoring Plan.

• Perform ongoing refinement of predictions ofbuilding vibration levels as directly measuredground vibration data become available, especiallywith regard to portal operations, as necessary.

• Support the public relations effort to ensure thatoutreach activities and materials address vibration.

• Respond to construction vibration issues and/orcomplaints quickly to re-assure the public that theirconcerns are being heard.

13 What mitigation is proposed for effects on viewsduring construction?

Mitigation Common to All Build AlternativesTo mitigate effects on visual quality during construction,WSDOT will design and place construction screens orbarriers to limit the visibility of work areas that wouldintrude on adjacent activities, such as pedestrians or thosegathering for sports events. WSDOT will also directtemporary construction site lighting away from nearbyresidences and businesses.

14 What mitigation is proposed for land use effectsduring construction?

Mitigation Common to All Build AlternativesMitigation for potential effects on land use duringconstruction activities will include providing advancenotice to property owners in the project area regardingdemolition and construction activities, utility disruptions,and detours. In addition, a construction website with a 24-hour project information line will be established andupdated regularly.

There would be no adverse effects on the General ServicesAdministration (GSA) Federal Office Building because thesubsurface acquisition for this project would not interferewith potential future development opportunities.

WSDOT is coordinating with the Port of Seattle to addresspotential effects that would result from the use ofTerminal 46 for construction staging. WSDOT will ensurethat safety, access, security, and operations during the useof the terminal for project activities are not compromised.

Construction traffic, noise, and dust will be mitigated, asdescribed in Questions 9, 11, and 24.

15 What mitigation is proposed for economic effectsduring construction?

Bored Tunnel AlternativeMitigation measures for transportation are also importantto mitigate effects on businesses and the economy.WSDOT will prepare a traffic management plan to ensurethat construction effects on local streets, property owners,and businesses are minimized. For more information onthe mitigation measures to be included in the plan, seeQuestion 9.

The following mitigation measures are intended tocounteract the diminished quality of the businessenvironment for those businesses adjacent to constructionactivities. These measures would maintain access and thegeneral setting for businesses and potential customers thatexisted before the project-related construction. WSDOTwill implement the following mitigation measures:

• Minimize obstructions and/or delays along theroutes to facilitate access to businesses, homes,cruise ships, ferry terminals, and waterfrontattractions.

• Avoid all work in the City right-of-way fromThanksgiving Day through January 1 in the areabounded by Columbia Street, Second Avenue, S. King Street, and Alaskan Way unless a City-approved variance is obtained.

• Use signage and a communications plan to informpeople about businesses open during construction.

Additional mitigation measures to reduce effects oneconomics would be related to communicatinginformation and maintaining pedestrian access. WSDOTwill continue to prepare a public outreach andcommunications plan each year during construction,which will include, among other things, outreach activitiesdesigned to provide notification about constructionactivities, pedestrian detours and parking changes duringconstruction so that businesses can inform their clients,


customers, and vendors. Public outreach activities andcommunications will be ongoing during projectconstruction.

Cut-and-Cover Tunnel AlternativeIn addition to the mitigation measures discussed above forthe Bored Tunnel Alternative, WSDOT could provideexperts in business marketing to give technical assistanceto affected businesses to help them operate duringdisruptive portions of the project. If implemented, thismeasure would be designed specifically for businessesabutting the project area along the waterfront and in themanufacturing and industrial centers.

Elevated Structure AlternativeMitigation measures would be the same as discussed abovefor the Bored Tunnel and Cut-and-Cover TunnelAlternatives.

16 What mitigation is proposed for parking effects during construction?

Mitigation Common to All Build AlternativesThe project has allocated $30 million to mitigate parkingeffects during project construction, and specific strategiesare being developed. The Seattle Department ofTransportation (SDOT), in coordination with WSDOT, hasconducted parking studies as part of the process todevelop mitigation strategies and better manage the city’sparking resources. Potential strategies to offset the loss ofshort-term parking in the central waterfront includeproviding new or leased parking and increased utilizationof and access to existing parking. The City-led CentralWaterfront Project is currently evaluating these strategiesin the context of improved access to the central waterfront.The City will recommend strategies that could beimplemented between 2011 and 2018. SDOT willimplement the final parking mitigation strategies based onthese recommendations.

WSDOT will identify appropriate parking options forconstruction workers, as necessary, and will discourage

their use of short-term visitor or customer parking in theproject vicinity.

17 What mitigation is proposed for effects on historicresources during construction?

Mitigation Common to All Build AlternativesAdverse effects due to traffic, noise levels, vibration, andair quality would impact historic resources adjacent toproject construction. Therefore, the mitigation measuresimplemented to address those effects would also minimizeeffects on historic resources.

In addition, WSDOT will minimize effects on historicresources by implementing the following measures:

• Provide construction traffic mitigation, as described in Question 9

• Compliance with construction management plans, such as the Fugitive Dust Control Plan andSpill Prevention, Control, and Countermeasure(SPCC) Plan

• Ensure access to stores, offices, and residences inhistoric areas

• Minimize disruptions of utility service in historicareas and for historic buildings during construction

• Use newsletters, websites, posters, community e-mailupdates, community events, and other methods ofcommunication to keep property owners, residents,businesses and employees in historic districts and inother historic buildings informed aboutconstruction issues

• Provide parking mitigation, as described in Question 16

Specific mitigation measures to address adverse effects ofthe Bored Tunnel Alternative are outlined in aMemorandum of Agreement between WSDOT, Federal

Highway Administration (FHWA), State HistoricPreservation Officer (SHPO), affected tribes, and otherconsulting parties. These measures are discussed in thesection below. If one of the other build alternatives isselected, a Memorandum of Agreement will be developedto outline the mitigation needed for that alternative.

Mitigation Specific to the Bored Tunnel AlternativeWSDOT has outlined mitigation for adverse effects onhistoric resources in a Memorandum of Agreementbetween WSDOT, FHWA, SHPO, affected tribes, and otherconsulting parties. The requirements of the Memorandumof Agreement include the following measures, to beimplemented by WSDOT:

• Historic building monitoring and preparation ofsettlement management plans for each historicbuilding prior to start of proposed tunneling.

• Establish a claims and repair process to repair anydamage to buildings. The process will include:

– The damage claim submittal process;

– The process by which damage claims will beinspected and evaluated;

– The process for and personnel involved inpreparing damage evaluations, repair costestimates, findings and recommendations;

– The process for making and documentingrepairs based on the reported cost estimatesand recommendations; and

– The process for making appeals.

A licensed architect with a background in historicarchitecture, who meets the professionalqualifications outlined in the Memorandum ofAgreement, will participate in the claims and reviewprocess involving any historic buildings within theArea of Potential Effects.


Damage caused by the project will be repaired inkind and in accordance with the Secretary of theInterior’s Standards for the Treatment of HistoricProperties and in compliance with the City ofSeattle’s Municipal Code, as appropriate. Asrequired, there will be review and approval by thePioneer Square Preservation Board, the SeattleLandmarks Preservation Board, the Pike PlaceMarket Historical Commission, or Washington StateDepartment of Archaeological and HistoricPreservation for National Register of Historic Placeseligible, but not locally designated, buildings.

• In the unlikely event that any one of the historicbuildings suffers significant structural damage,emergency measures will be implemented asoutlined in the Memorandum of Agreement.

WSDOT has outlined mitigation for adverse effects on thePioneer Square Historic District, in the Memorandum ofAgreement. The requirements include:

• Development and implementation of acommunications plan.

• Establishment of a project information center to provide information and educationalopportunities to the public, residents, andbusinesses in Pioneer Square.

• Development and implementation of marketingactivities to promote Pioneer Square.

• Development and implementation of a trafficmanagement and construction coordination plan.

To minimize damage to the Western Building, WSDOTwill implement a building protection solution. WSDOT has prepared a conceptual design for this which includes foundation stablization, the stabilization of existing cracked structural elements, the installation oftemporary shoring inside the building, the construction of a temporary exterior steel frame around the building,

and a stabilizing regime of compensation grouting intothe soil for added stability.

Approximately 118 tenants of the Western Building wouldbe permanently relocated. Most of the tenants of thisbuilding are artists who use the building for studio orworkspace. The artists benefit from their proximity to eachother and the associated opportunities to share ideas andinspiration. Because of this, WSDOT is actively working tosupport the efforts of the artists by finding replacementaccommodations nearby, either in the Pioneer Squareneighborhood, if feasible, or in other locations in thegreater Seattle area where the individual artists maychoose to relocate.

The Polson Building is a historic building adjacent to theWestern Building. WSDOT will avoid settlement damageto the Polson Building by using compensation grouting tostabilize the surrounding soil.

For the Lake Union Sewer Tunnel, the project has alreadymodified the design of the Republican Street off-ramp toraise it to minimize impacts to the manhole shaft. WSDOTwill mitigate the adverse effect on the sewer tunnel byrecording the structure and researching its history as partof a National Register nomination form. Mitigationmeasures for settlement effects on non-historic buildingsare discussed in Question 28.

18 What mitigation is proposed for effects onarchaeological resources during construction?

Mitigation Common to All Build AlternativesWSDOT will develop an Archaeological Treatment Planwhich will guide the actions of cultural resourcesprofessionals for archaeological investigations and datarecovery. The Archaeological Treatment Plan also willinclude the protocol for handling unanticipatedarchaeological and human remains discoveries, andarchaeological monitoring during project construction.

The purpose of these plans is to make sure thatarchaeological resources, if unearthed during construction,

are handled in compliance with applicable regulations.This plan will be developed before excavation begins andwill remain in effect until construction is completed.

19 What mitigation is proposed for effects on parks,recreation, and open space during construction?

Adverse effects due to traffic, noise levels, vibration, andair quality would have effects on parks, recreation, and open space adjacent to project construction. Themitigation measures implemented to address thoseconstruction effects would also minimize effects onrecreational facilities.

Bored Tunnel AlternativeWSDOT will implement the following mitigation measuresto address potential adverse effects on parks, recreation,and open space:

• Provide ADA-compliant detour routes when trails,pedestrian bridges, or other pathways are closedtemporarily. Detours would be within a reasonabledistance of the closed facility.

• Coordinate regularly with park and recreationfacility operators to ensure that changes in viaductremoval activities and associated changes in accesspoints and corridors are known in advance.

• Continue public outreach through projectconstruction to keep the community informedabout temporary closures or rerouting of facilities,and other potential effects.

As appropriate, WSDOT would provide way-findingsignage to indicate detour routes along the corridor andon streets surrounding the construction areas.

Cut-and-Cover Tunnel AlternativeMitigation measures would include those discussed abovefor the Bored Tunnel Alternative and the measuresdiscussed below.


To address disruption of existing and usual patterns ofmovement along the waterfront during construction,which has the potential of reducing the overallattractiveness of the waterfront as destination, WSDOTwould implement the following strategies:

• Provide temporary overwater pedestrianconnections to allow continuity between Piers 54and 59 while the waterfront promenade is not inoperation

• To the extent possible, schedule constructionactivities to quickly complete waterfront work andrestore a continuous, if temporary, corridor as soon as possible, while work continues on relatedactivities that do not directly disrupt movementalong the corridor

In addition, WSDOT could implement the followingmeasures, with the decision to be made later in projectplanning:

• Provide specific locations for charter bus parkingwith clear and convenient access to the waterfront to preserve and enhance group attendance

• Publicize alternative modes of access to thewaterfront by public transit or by dedicated transit service on peak demand days from park-and-ride lots or other facilities

The effects of noise and vibration on passive recreationactivities such as walking, picnicking, and viewing theaesthetic amenities of the area will be addressed byconstruction scheduling and any noise attenuationmeasures, as required by the Major Public ProjectConstruction Noise Variances. See Questions 11 and 12 fordiscussions of potential noise and vibration mitigation.

If determined necessary during project final design or asconstruction progresses, access to Blake Island cruises(Pier 55) would be relocated to portions of the waterfrontless affected by cut-and-cover tunnel construction or

seawall reconstruction. Potential locations may includeportions of Terminal 46, Pier 66, or Pier 70 within thegeneral area or the Pier 91 or Fauntleroy areas. Suchrelocation would be communicated through publicinformation methods to ensure that potential users areaware of the change.

Because of disruptive construction along the waterfront,the public may perceive that the waterfront would not be aconvenient or pleasant environment to visit. WSDOTcould work with tourism groups, local businesses, existingstakeholder groups, the media, and others to ensurecritical access to the waterfront is maintained and accurateinformation about current and long-term constructionactivities is shared.

To mitigate impacts on recreational resources that dependon admission fees, such as the Seattle Aquarium or QwestField, mitigation measures that address access and parkingeffects, as discussed in Questions 9 and 16 would help toalleviate the perceived hassle of visiting the waterfront.

Elevated Structure AlternativeMitigation measures would be the same as discussed abovefor the Bored Tunnel and Cut-and-Cover TunnelAlternatives.

20 What mitigation is proposed for effects onneighborhoods and community services or resourcesduring construction?

Mitigation Common to All Build AlternativesAdverse effects due to changes in traffic, parking, noiselevels, and the relocation of businesses would have varyingeffects on the overall social environment that defines howneighborhood residents, workers, and visitors interact.Therefore, the proposed construction mitigation measuresfor other disciplines, such as transportation, visual quality,noise, public services and utilities, and economics wouldalso reduce effects on neighborhoods.

Each year, WSDOT develops a comprehensive publicoutreach and communications plan, which incorporates

the use of a variety of communication methods, such aswebsites, community e-mail updates, media relations,public meetings, interviews with social service providers,presentations to neighborhood groups, written materials,and information booths at community events tocommunicate project information and engage agencies,tribes, and the public.

The purpose of the communications plan is to make surethat the public is informed about construction happenings,such as detours and road closures. An informed public willresult in less confusion and frustration for thecommunities located near the project area, and better tripplanning for those traveling near construction activities.

During construction, WSDOT will continue to holdcommunity briefings, maintain a presence at communityevents, and provide project information to the public viacommunications, such as e-mails and folios.

WSDOT will also maintain a project 24-hour hotline and e-mail so that people can call to receive information aboutthe project or express a concern. If a concern is expressedby a member of the public, WSDOT will respond in atimely manner and work to address the issue.

WSDOT will communicate with owners and operators ofcommunity facilities, park and recreation facilities,religious and cultural institutions, social and employmentservices, and government agencies, throughoutconstruction of the project to ensure that currentconstruction activities and project milestones are knownand concerns are addressed when possible. In addition,WSDOT will implement the following mitigation measuresto address potential effects on neighborhoods andcommunity services or resources:

• Coordinate with community service or resourceproviders to determine whether additional orspecial mitigation measures are needed.

• Work with representatives of Seattle Center, SafecoField, Qwest Field, and the Qwest Field Event Center


to develop specific mitigation measures to addressvehicle and transit access and parking issues relatedto workers and attendees at large events, as needed.

• Work with representatives of religious institutionsclose to construction zones to develop mitigationmeasures to address potential noise that couldadversely affect services, meditation sessions, orother events, as needed.

• Include government agencies located near theproject construction areas on distribution lists tonotify them about planned construction activities.

Mitigation Specific to the Bored Tunnel AlternativeApproximately 118 tenants of the Western Building wouldbe permanently relocated. Most of the tenants of thisbuilding are artists who use the building for studio orworkspace. WSDOT is actively working to support theefforts of the artists by finding replacementaccommodations.

21 What mitigation is proposed for effects on minoritiesand low-income people during construction?

Mitigation Common to All Build AlternativesIn addition to the public outreach and communicationplan outlined above in Question 20, Mitigation Commonto All Build Alternatives, WSDOT will implement thefollowing measures to address effects on specific adjacentproviders of services to minority and/or low-incomepeople:

• Identify a safe and ADA-compliant pedestrian route between Pioneer Square/downtown and theSt. Martin de Porres shelter to allow movement ofpeople to and from the shelter throughout theconstruction period. Information about the routewould be distributed to social service providers,placed in proper notification areas, and markedwith directional signs.

• Work with The Compass Housing Alliance (formerlyThe Compass Center), Heritage House, Bread ofLife Mission, Pike Market Senior Center, PlymouthHousing Group, Catholic Seamen’s Club, and Roseof Lima House to identify concerns and solutionsfor potential construction-related effects.

WSDOT will implement these measures to address generaleffects on minority and/or low-income populations:

• Ensure access to buildings, properties, and loadingareas used by social service providers duringconstruction.

• Hold briefings and interviews with social serviceproviders to keep them up to date on the projectand to gather feedback as the project progressesfrom design through construction.

• Work with citizen participatory groups and serviceproviders, such as committees, task forces, advisorybodies, housing authorities and social services toidentify, communicate and assist disadvantagedpopulations with transportation options.

• Cooperate with social service providers on emergentissues that affect minority and low-incomepopulations.

• Ensure continuous utility service duringconstruction to the extent feasible. If periodicoutages are unavoidable, provide ample notice.

• Work with homeless service providers,neighborhood groups, the City, and King County toensure the safety and survival of nearby homelesspeople during construction of the newtransportation facilities. Nearby homeless peopleinclude those living outdoors or in vehicles locatedunder or near transportation facilities in the project area.

• Secure construction sites to prevent entry andinjuries (especially by homeless persons). Lightconstruction areas during the night and conductsecurity sweeps to look for unauthorized peopleseeking shelter within construction sites.

• Train construction workers on appropriateinteractions with homeless persons they mayencounter at construction sites.

• Maintain regular communication with minority-owned businesses, if identified, affected byconstruction-related traffic congestion.

• Distribute flyers to service providers, ethnic media,and local businesses and place flyers on windshieldsof cars parked in long-term parking areas; theseflyers should specify when vehicles should be moved.List other long-term parking alternatives in the area,if any exist.

22 What mitigation is proposed for effects on publicservices during construction?

Mitigation Common to All Build AlternativesWSDOT will coordinate with public service providersthroughout project design and construction to ensure thatproject effects are understood in advance, planned for,and minimized. The purpose of this coordination is toeliminate or reduce disruptions to public services that mayoccur during project construction.

WSDOT will coordinate with the City and Port of Seattlepolice and fire departments, regional transportationagencies, and other related agencies during the finaldesign of the selected alternative. This coordination willmake sure that reliable emergency access and alternativeplans or routes to avoid preventable delays in responsetimes are developed, and to ensure that generalemergency management services are not compromised.Providers of emergency and nonemergency public serviceswill be notified early on of detours and lane restrictions.


When water lines and fire hydrants are being relocated,WSDOT will coordinate in advance and provide schedulenotifications to the affected fire stations to allow advancedplanning and to reduce the effects associated with serviceinterruptions.

WSDOT will coordinate with construction personnel and,if necessary, with the City and Port of Seattle policedepartments to ensure that adequate staffing is availableduring construction for traffic and pedestrian movementcontrol and other necessary policing efforts.

WSDOT will implement the following mitigation measuresto address effects on specific public services:

• School Buses – The Seattle School District hasestablished rerouting plans for use when theexisting viaduct is unusable. It is anticipated thatthese rerouting plans would be implemented whenSR 99 is closed.

• Solid Waste Collection, Disposal, and Recycling –Waste processing haulers and facilities will beinformed that additional loads would be deliveredduring construction. The area transfer stations andregional landfills have sufficient capacity toaccommodate the construction waste and debrisgenerated from construction activities associatedwith any of the build alternatives.

WSDOT would also implement the following mitigationmeasures to address effects on these public services, if suchmeasures are found necessary to adequately addressconstruction effects:

• Law Enforcement Services – The need for additionalpolice support services could be addressed byproviding additional permanent or temporary lawenforcement officers and/or stations.

• Fire and Emergency Medical Services – Responsetimes for fire and emergency medical services couldbe affected, particularly during construction.

Intelligent traffic signal controls at signalizedintersections would be used as a partial mitigationmeasure. If intelligent traffic signals cannotadequately mitigate the effects on emergencyresponse, then additional staff, equipment, andfacilities may be proposed.

23 What mitigation is proposed for effects on utilitiesduring construction?

Mitigation Common to All Build AlternativesWSDOT will coordinate with utility providers on utilityrelocation plans that identify impacts and temporary andfinal locations. WSDOT will develop constructionsequence plans and coordinate schedules for utility workto minimize service disruptions and provide ampleadvance notice when service disruptions are unavoidable,consistent with utility owner policies. Affected utilityproviders will review and approve relocation plans andservice disruptions before construction begins.

Specific mitigation measures for effects on utilities will bedeveloped during the ongoing coordination processbetween WSDOT, Seattle Public Utilities, Seattle City Light,and other providers. Some of the potential mitigationmeasures for effects on utilities during construction are:

• Assemble a multidisciplinary task force to monitorsettlement during construction (Bored TunnelAlternative only).

• Ensure all utilities are accessible during construction.

• Expose critical utilities before beginningconstruction in the vicinity.

• Coordinate utility relocation plans with utilityowners and customers to minimize the impacts ofservice disruptions.

• Require contractors to comply with utility ownernotice requirements for planned outages.

• Coordinate with utility owners to ensure that ownercontingency plans for management of any potentialutility service disruptions are accommodated.

• Provide backup on-site electrical generation, asneeded, to minimize or eliminate power outages tocustomers as determined by Seattle City Light on acase-by-case basis.

• Coordinate construction-related mitigation withother construction projects in the vicinity tominimize utility and traffic disruptions.

In addition to the above potential mitigation measures,Washington State law and standard specifications requireadherence to additional measures during construction:

• If inadvertent damage to utilities occurs duringconstruction, the appropriate utility provider wouldbe contacted immediately to restore service.WSDOT will also be required to take immediatemeasures to ensure public safety and protectproperty.

• Traffic revision equipment and personnel would beprovided as required during utility relocations.

• Construction activities in the street right-of-waywould be conducted during off-peak hourswhenever possible to lessen traffic effects.

• All utilities determined to need protection in place would require a protective measure, such as pipe and conduit support systems, trench sheeting, and shoring.

• Construction techniques to avoid or minimizevibration effects on utilities would be used whereneeded. Such techniques may include using drilledshafts in lieu of driven piles.

• A safety watch would be provided throughcoordination with Seattle City Light. The safety


watch would minimize the interruption of power tocustomers and to speed up power restoration in theevent of accidental interruption of power caused byproject construction. Critical utilities, such astransmission ducting, may need to be exposedduring construction to lessen the chance of damagethat could result in unplanned outages.

24 What mitigation is proposed for air quality effectsduring construction?

Mitigation Common to All Build AlternativesA Memorandum of Agreement between WSDOT andPuget Sound Clean Air Agency is in place to identifyappropriate mitigation to help eliminate, confine, orreduce construction-related emissions, in the form offugitive dust, for WSDOT projects. The Memorandum of Agreement will apply to this project.

Per the MOA, WSDOT will create a plan for controllingfugitive dust during construction. This fugitive dustcontrol plan will reduce air pollutant emissions near theconstruction site, including residences located alongBattery Street adjacent to the open street grates. Somemeasures that will be included in the plan are:

• Cover trucks transporting materials to reduceparticulate emissions during transportation onpaved public roads

• When feasible and where practicable, routeconstruction trucks away from residential andbusiness areas to minimize annoyance from dust

• Coordinate construction activities between WSDOT and the Seattle Department ofTransportation with respect to other projects in the area to reduce the cumulative effects ofconcurrent construction projects

In addition to the strategies detailed above, othermeasures for reducing air quality effects duringconstruction include:

• Spray exposed soil with water or other dustpalliatives to reduce emissions and deposition ofparticulate matter

• Remove particulate matter deposited on pavedpublic roads to reduce mud and windblown dust on area roadways

• Enclose conveyor systems used to transport dirt from the tunnel excavation sites to the waterfront, if barges are used

WSDOT’s traffic management plan will include bestmanagement practices to reduce activities such as idlingand traffic congestion, which produce concentratedvehicle emissions. Implementation of this plan will alsomitigate the effects of vehicle emissions on air quality.

The mitigation measures to reduce energy consumptionand greenhouse gas emissions (discussed below) also willmitigate air quality effects.

25 What is proposed to minimize energy consumption andgreenhouse gas emissions during construction?

Mitigation Common to All Build AlternativesThe traffic management plan that WSDOT will develop forthe project includes detours and strategic constructionplanning to continue moving traffic through the area andreduce backups to the extent possible. Construction areas,staging areas, and material transfer sites will be set up in away that reduce standing wait times for equipment, engineidling, and the need to block the movement of otheractivities on the site. This traffic management plan willhelp minimize energy consumption through thepromotion of reduced vehicle and equipment idling,which leads to reduced fuel consumption. Because fuelconsumption is directly related to greenhouse gasemissions, any steps taken to minimize fuel consumptionwill reduce greenhouse gas emissions as well.

In addition to the traffic management plan, WSDOT willimplement the following other measures to reduce energyconsumption during construction:

• Use electrical equipment where feasible

• Use relatively new, well-maintained equipment

• Promote ridesharing and other efforts, such asWSDOT’s Commute Trip Reduction program, toreduce commute trips for employees working on the project

• Coordinate construction activities with otherprojects in the area to reduce the cumulative effectof concurrent construction projects

26 What mitigation is proposed for effects on waterresources during construction?

Bored Tunnel AlternativeWSDOT will incorporate water quality BMPs into theproject design to ensure that the proposed project willcomply with the applicable federal, state, and localregulations to protect water resources. WSDOT may berequired to obtain a National Pollutant DischargeElimination System (NPDES) construction permit fromthe Washington State Department of Ecology (Ecology) ifthe extent of exposed soils and anticipated dischargelocations require one.

Construction-related runoff and dewatering water will bedischarged to the combined sewer system for treatment atthe West Point Wastewater Treatment Plant. WSDOT willtreat stormwater runoff from active construction areas andany dewatering water that reaches contaminant thresholdsas necessary to meet the requirements of King Countybefore discharge to either the combined sewer or theseparated storm drain. If required, WSDOT will obtain awastewater discharge permit or authorization from KingCounty before discharging construction stormwater ordewatering water to the combined sewer. Depending onthe volumes and timing, if discharging dewatering flows to


the stormwater or combined sewer system is not feasible,WSDOT will use off-site disposal.

WSDOT will avoid, minimize, and mitigate constructioneffects on water resources by developing, implementing,and updating as site conditions change throughout theduration of project construction, the following plans:

• Temporary Erosion and Sediment Control Plan• Spill Prevention, Control, and Countermeasures Plan• Concrete Containment and Disposal Plan

Each of these plans include performance standards basedon state regulations, such as turbidity and total suspendedsolids levels in stormwater discharged from constructionstaging and work areas, which are established to eliminateor reduce pollutants entering bodies of water.

Cut-and-Cover Tunnel AlternativeThe mitigation measures would be the same as thosediscussed above for the Bored Tunnel Alternative.

In addition, WSDOT will implement mitigation measuresto minimize or prevent construction-related pollutantsfrom entering Elliott Bay during the seawall replacement:a containment system would be installed on the waterwardside of the existing seawall.³ The following steps would befollowed for construction of the containment system:

1 The existing seawall will be surveyed for size andlocation of cracks and other potential leakage points.

2 Temporary repairs will be made to the existingseawall to retain upland grout when it is placed.

3 A turbidity curtain will be installed to minimizeturbidity in the construction area and prevent waterquality impacts outside the work area.

4 A movable containment panel will be installedadjacent to the existing seawall, includingimpervious matting to be placed over the riprapadjacent to the seawall. The size and location of

the panel-mat system would be determined by the secant pile installation and grouting operations.

If spoils from jet grouting were dewatered on site, atemporary treatment facility will likely be required to treatthe water before discharge.

If the removal of riprap were necessary, WSDOT will installa turbidity curtain before starting this task.

Outfalls that require replacement will be constructed atthe same time as the seawall construction activities, usingsimilar BMPs. WSDOT would implement measures tocontinue drainage service during construction during thereplacement of stormwater outfalls and combined seweroverflow structures.

Elevated Structure AlternativePotential mitigation measures would be the same asdescribed above for the Bored Tunnel and Cut-and-CoverTunnel Alternatives.

27 What mitigation is proposed for effects on fish, aquatic,and wildlife species and habitat during construction?

Bored Tunnel AlternativeThe primary activity that could affect fish and otheraquatic species is the operation of a barge landing facilityalong Terminal 46. This operation would use existingfacilities, and no in-water construction would be required.

WSDOT will implement construction BMPs to minimize oreliminate effects on species or their habitat. Standardconstruction BMPs will minimize short-term constructioneffects, including the discharge of sediment from thedisturbed construction areas into Elliott Bay.

WSDOT will handle all pollutants to avoid contaminatingsurface water in the study area. Materials that modify pH,such as cement, cement grindings, and cement saw cutting,will be managed or isolated to minimize the spread ofthese materials by surface water runoff or other means ofentering the area waterways; see Question 26 for details

about measures to avoid and minimize effects on waterresources. WSDOT will ensure that all work activitiescomply with the necessary water quality requirements.

Unlike the other build alternatives, the Bored TunnelAlternative would not include the replacement of theElliott Bay Seawall, so no in-water construction activitieswould take place. Since there would be no effects on fishand aquatic resources as a result of in-water work,mitigation for such effects is not proposed.

Cut-and-Cover Tunnel AlternativeMitigation measures would be similar to those describedabove for the Bored Tunnel Alternative.

However, because the Cut-and-Cover Tunnel Alternativeincludes replacing the seawall, WSDOT would implementstandard in water construction BMPs, such as silt curtains,sound attenuation measures, and cofferdams to reduce oreliminate the potential effects of in-water constructionactivities on aquatic species and habitat. WSDOT willreplace any habitat loss or reduction in function withappropriate mitigation measures, as required by applicablefederal, state, and local regulations that govern fish,aquatic resources, wildlife species and habitat. Specificmitigation measures to replace habitat loss and functionwould be established if this alternative is selected.

WSDOT will mitigate for the effects of the temporaryaccess bridge to the Colman Ferry dock and the pedestrianaccess walkways with the eventual removal of thesestructures and the permanent increase in aquatic habitatprovided by moving the Elliott Bay seawall landward of theexisting position.

Elevated Structure AlternativePotential mitigation measures would be similar to thosedescribed above for the Cut-and-Cover Tunnel Alternative.

3 Parsons Brinckerhoff 2006.


28 What mitigation is proposed for effects on soils andgroundwater during construction?

Mitigation Common to All Build AlternativesMany of the effects on soils and groundwater duringconstruction can be mitigated with BMPs, propertechniques, and good workmanship. Project constructionwill be observed by experienced engineers or techniciansto ensure compliance with WSDOT standards.

SettlementTo mitigate for effects related to settlement, WSDOT will:

• Perform soil improvement in areas where existingstructures need to be protected from settlement; tobe determined during final design.

• Use reinjection wells near the excavation area,supplied by water from the dewatering operation, tominimize settlement that may result fromdewatering activities.

• Establish a claims and repair process by whichowners of buildings, including historic buildings,can file claims for damages to their properties thatresult from the project; see Question 17 for moredetails about the claims and repair process.

• Use structural fill material appropriate for siteconditions to construct fills.

• Perform construction sequencing so that projectstructures that could be sensitive to settlement areinstalled after most of the fill settlement hasoccurred, if necessary.

• Avoid placing stockpiles directly over utilities orpavements without appropriate subsurface supportto prevent potential damage. In areas where this isnot possible, stockpile heights could be limited toavoid damage to underlying utilities or pavement.

• If necessary, shore temporary excavations to mitigate potential sloughing of soils and lateralmovement or settlement of nearby existing roadways, railways, structures, and utilities.

In addition to the measures described above, WSDOTwould use these measures to address settlement, if needed:

• Preload the site as needed in areas where siteavailability and time schedules allow.

• Perform soil improvement or alternativeconstruction methods (e.g., use of compressiblefoundation material over hard spots or installationof structural elements) to mitigate for potentialdifferential settlement.

• Relocate existing utilities located beneath or nearproposed fill embankments if loads and settlementswould cause damage to the utilities. Alternatively,monitor utilities to determine if settlementtolerances are being exceeded.

• Use lightweight fill materials in areas wheresettlements must be minimized and alternativemeasures are not feasible.

Soil ImprovementWSDOT will implement soil improvement measures, suchas jet grouting and compensation grouting, to stabilize softsoils where necessary (except between S. Main Street and S. Washington Street to avoid potential archaeologicaldeposits).

Erosion and Sediment ControlWSDOT will implement BMPs for erosion and sedimentcontrol. Erosion and sediment control measures suitableto specific site conditions will be used. Site conditions willdictate the possible BMPs used, which include usingconstruction staging barrier berms, covering loads duringtransport, filter fabric fences, temporary sedimentdetention basins, and slope coverings to contain sedimenton site.

Temporary erosion and sediment control plans will beprepared for approval in accordance with BMPs includedin the current Seattle Municipal Stormwater Code(Ordinance 123105) and the Seattle Municipal GradingCode (Ordinance 123107), as appropriate, and theWSDOT Highway Runoff Manual.⁴

Proposed mitigation measures will be consistent withstormwater design and treatment procedures in thecurrent version of the WSDOT Highway Runoff Manual andalso will follow the permits necessary for this project.

Bored Tunnel AlternativeIn addition to the mitigation measures common to all thebuild alternatives, the following measures are proposed forthe Bored Tunnel Alternative:

• Dewatering systems will be designed to minimize thedrawdown of the water table outside of the excavation in areas where adjacent structuresmay be affected. Potential mitigation measuresinclude the use of groundwater recharge wells,dewatering in small sections, or use of barriers (e.g.,sheet piles) to isolate the water table within theexcavation.

• Use soil improvement, such as jet grouting and deepsoil mixing, along the bored tunnel alignment tostabilize soft soils and reduce the potential forsettlement.

• Control and monitor the tunnel boring machine tominimize ground loss and settlement during tunnelboring.

• Inspect critical structures and utilities likely to beaffected by tunneling-induced settlement prior toconstruction to evaluate their existing condition andpotential for damage.

• Instrumentation may be installed to monitor groundmovements on and below the ground surface duringtunnel boring; see Question 12 for more 4 WSDOT 2010.


information on vibration monitoring during tunnelboring.

Cut-and-Cover Tunnel AlternativeThe mitigation measures discussed above for the BoredTunnel Alternative would apply for this alternative, exceptfor measures directly related to the tunnel boring machineused for the Bored Tunnel Alternative.

Elevated Structure AlternativeThe mitigation measures common to all build alternativeswould apply for this alternative.

29 What mitigation is proposed for effects related tohazardous materials during construction?

For all build alternatives, WSDOT will prepare a SpillPrevention, Control, and Countermeasures Plan, whichoutlines procedures to be used if a spill of hazardousmaterials occurs; a fugitive dust plan to control dust-generating activities; a water quality monitoring plan; anda Soil and Groundwater Management Plan that addresseshandling and disposal of known and unanticipatedcontamination.

For contamination already identified by WSDOT,additional investigations and characterization may beperformed to determine whether the project woulddisturb contaminants present, and appropriate necessarymitigation. For instance, if WSDOT’s final constructionplans are unable to avoid previously identified sitecontamination, additional investigations, characterizations,and surveys would be performed to support appropriatemanagement and disposal of the contaminated materials.These investigations may include environmental siteassessments, contamination delineations, asbestos surveys,lead surveys, and/or geophysical surveys.

WSDOT will manage and dispose of contaminated soil inaccordance with applicable permits and regulations andwill implement construction techniques that minimizedisturbance, release, and migration of contaminants in theproject area. Construction activities will be selected inorder to reduce the spread of contamination; specific

construction methods, such as use of special drillingmethod or dewatering wells that minimize drawdown, maybe necessary to prevent cross-contamination and tominimize the migration of contaminated groundwaterduring construction.

Groundwater that is encountered during projectconstruction dewatering will be handled in accordancewith applicable permits and regulations. Shallowgroundwater is more likely to contain contaminants than groundwater from deeper soil. Water qualitytreatment for shallow dewatering could consist of storingthe water to allow particles to settle or reducing suspendedparticles by adding chemical flocculants. If required,WSDOT will treat contaminated dewatering water toacceptable standards according to the Washington StateSurface Water Quality Standards prior to discharging to waters of the state or King County, or WSDOT will dispose of it offsite at a facility permitted to accept contaminated water.

To reduce the effect of odors due to contaminants thatcould become airborne during construction or demolitionactivities, engineering controls would also be implemented,such as ventilation with fans to dissipate volatilecontaminants and air filtration methods to removeparticulates and volatile compounds.

INDIRECT EFFECTS

30 Are mitigation measures proposed for indirect effects?Indirect effects, such as people changing where they shop,where they eat out, or what services they use as they adjusttravel patterns during project construction are possible. Inaddition, if the Bored Tunnel Alternative or Cut-and-CoverTunnel Alternative is selected, a new tunnel facility maysupport renovation and revitalization of existing urbanland uses in some areas because the viaduct structurewould be removed and new development on vacant orunder-used property or redevelopment may take placearound the new Alaskan Way surface street. However,project indirect effects are not expected to be significant;

mitigation beyond what would be implemented to addressdirect effects is not proposed.

EFFECTS NOT MITIGATED

31 What permanent project effects would not bemitigated?

In general, WSDOT avoids, minimizes, or mitigatespermanent effects associated with the project. However,the permanent effects discussed below will not bemitigated.

Transportation ChangesThe tolled and non-tolled Bored Tunnel and Cut-and-Cover Tunnel Alternatives would permanently changetravel patterns compared to the existing viaduct. TheElevated Structure Alternative would maintain accesssimilar to the existing viaduct. Changes to travel patternsmay permanently increase travel times for some routes.However, changes to travel patterns, increased travel times,and/or changes to access will not be mitigated.

Parking LossesAll three of the build alternatives are expected to result ina reduction in parking facilities relative to existingconditions, but there are no proposed mitigationmeasures for permanent parking losses. No mitigation isproposed because the parking removals are consistent withSeattle’s Comprehensive Plan:⁵ Goal TG18 indicates thatin making decisions about on-street parking,transportation is the primary purpose of the city’s street system.

NoiseCompared to 2015 existing conditions, the number ofmodeled sites that exceed the noise abatement criteria in2030 would be:

• Reduced by 12 sites with the Tolled Bored Tunnel• Reduced by 13 sites with the Non-Tolled Bored Tunnel• Reduced by 10 sites with the Tolled Cut-and-Cover

Tunnel

5 City of Seattle 2005.


• Reduced by 13 sites with the Non-Tolled Cut-and-CoverTunnel

• Increased by 4 sites with the Tolled Elevated Structure• Increased by 4 sites with the Non-Tolled Elevated

Structure

Measures for noise abatement as required by federalregulations (23 CFR 772) were evaluated for eachalternative to determine what measures are feasible andreasonable. These measures include the following:

• Traffic management – measures include timerestrictions, traffic control devices, signing forprohibition of certain vehicle types (e.g.,motorcycles and heavy trucks), modified speedlimits, and exclusive lane designations. For example,speed limits could be reduced, but a reduction of 10 to 15 miles per hour would be required todecrease traffic noise by 5 dBA. Implementation of these measures for the sole purpose of noisemitigation would not be reasonable.

• Land acquisition for noise buffers or barriers –in an urban area such as the study area, this wouldrequire relocating numerous residents andbusinesses and would not be reasonable for thepurpose of noise mitigation.

• Realigning the roadway – the alignment is definedby available right-of-way and the design features ofthe project. The cost of realigning the roadwaywould not be reasonable exclusively as anoperational noise mitigation consideration.

• Noise insulation of buildings – this measure does not apply to commercial and residential structuresand is not eligible for federal funding.

• Noise barriers – to be effective, noise barriers would have to block access to the surface streets.There are no feasible mitigation measures to reducetraffic noise levels because the surface streets

provide local access to downtown and the waterfront throughout the central waterfront.

None of these measures were identified to be feasibleand/or reasonable for any of the build alternatives.

32 What temporary construction effects would not bemitigated?

WSDOT will implement mitigation measures to avoid orminimize effects during construction for all buildalternatives. However, it will not be possible to preventsome effects, even with mitigation. For many of the effectsdescribed in this chapter, some residual temporaryconstruction effects would remain. For example,mitigation measures will be in place during constructionto minimize noise impacts, but people near theconstruction area will still hear construction activities.Another example is pedestrian access. Mitigation will be inplace to maintain access for pedestrians, but there likelywill be periods when a favored pedestrian route istemporary closed. Similarly, access to the stadiums andwaterfront attractions will be maintained, but theconvenience of visiting these attractions will likely bediminished. Such residual effects are not expected to besubstantial and will be temporary as the project movesalong the corridor.

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