Seattle DOT Mercer Parcels

Facility Site ID: 27913 Cleanup Site ID: 14784

Current Status

Seattle DOT Mercer Parcels – Aerial view of Site and parcels.
Seattle DOT Mercer Parcels – Aerial view of Site and parcels.
This Site is part of a multi-property transaction associated with the Mercer Mega-Block Development project in Seattle’s South Lake Union neighborhood. The Seattle DOT Dexter Parcel Site is also part of the property transaction and development project. Please see the web page for Seattle DOT Dexter Parcel for details and documents related to that site. 






 訊息中文版 清理工作站信息 

 Información en español  Información del Sitio 

Factsheet
(2021)


Formal cleanup process moves forward
Ecology conducted a public comment period (December 6, 2021 – January 19, 2022) on a draft Prospective Purchaser Consent Decree (legal agreement) and associated cleanup documents for the Seattle DOT Mercer Parcels site. 

Ecology has reviewed and considered all comments received on the draft documents. Based on Ecology’s evaluation of the comments, no changes to the documents were necessary. (Download the Response to Comments.)

Final Prospective Purchaser Consent Decree (PPCD) – legal agreement that directs the Prospective Purchaser to implement cleanup of the Site in accordance with the Cleanup Action Plan (below) once it has completed its purchase.  

Final Remedial Investigation (RI) – describes contamination at the Site. To view RI appendices, please click the 'View Electronic Documents' link to the right.

Final Focused Feasibility Study (FFS) – evaluates and recommends a permanent cleanup action as the preferred alternative.

Final Cleanup Action Plan (CAP) – describes Ecology’s chosen cleanup plan and specifies cleanup standards and requirements for the Site.

State Environmental Policy Act – Determination of Non-Significance (SEPA) – evaluation and determination that the proposed cleanup at the Site is not likely to cause harm.

State Environmental Policy Act - checklist

Public Participation Plan (PPP) –  describes how Ecology will engage with the community and keep the public informed.


Online public meeting
On January 6, 2022, Ecology held an online public meeting to present on the cleanup projects.  You can view the slides for this presentation here:

Public presentation slides


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Join our email list to receive updates about the South Lake Union cleanup sites, including Seattle DOT Mercer Parcels. You may also email the Public Involvement Coordinator (listed under Contacts) to be added to the list. Unsubscribe at any time.

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Site Information

Current view of Site looking northeast from  the intersection of Mercer St and Dexter Ave N.
Current view of Site looking northeast from the intersection of Mercer St and Dexter Ave N.
The Seattle DOT Mercer Parcels Site is located in the South Lake Union neighborhood of Seattle. The property where the Site is located (Property) consists of two land parcels totaling 2.35 acres in size and is bounded to the north by Roy St, to the south by Mercer St, to the east by 9th Ave N, and to the west by Dexter Ave N. The Property contains the Site.

Site History
Past uses of the Property included auto repair and wrecking shops, fueling and service stations, a sign painting and retail painting business, a soap and chemical works, and private residences. During the 2010s, construction occurred to reroute the Broad Street underpass and facilitate Mercer Corridor improvements. In 2017, an investigation conducted as part of this project discovered contamination in soil and groundwater beneath the Property. More recently, the Property was a construction staging area. It is now vacant. 

Contamination

View of the Property showing historical locations of structures and streets, areas of contamination, and the proposed area of excavation.  Petroleum contamination is in red. cPAHs and arsenic contamination are in orange.  Lead contamination is in gray.
View of the Property showing historical locations of structures and streets, areas of contamination, and the proposed area of excavation. Petroleum contamination is in red. cPAHs and arsenic contamination are in orange. Lead contamination is in gray.
Investigations at the Site found the following contaminants in soil and/or groundwater:

•Gasoline-range petroleum hydrocarbons

•Diesel-range petroleum hydrocarbons

•Benzene

•Lead



These contaminants are present at levels that exceed allowable standards under the state’s cleanup law, the Model Toxics Control Act (MTCA), and will be addressed during the Cleanup Action.

Other hazardous substances are present on the Property at levels that exceed MTCA cleanup standards but are not considered constituents of concern for the Site. These substances include carcinogenic polycyclic aromatic hydrocarbons (cPAHs), arsenic, and chlorinated solvents, and are associated with separate contaminated sites in the vicinity of the Property. The proposed cleanup action for the Site and planned redevelopment of the Property will concurrently address portions of these other sites.

Future Property Use

Image of proposed redevelopment.  Credit: Alexandria Real Estate Equities, Inc.
Image of proposed redevelopment. Credit: Alexandria Real Estate Equities, Inc.
Future development plans include constructing two 13-story towers separated by a right-of-way. The two separate towers will share a below-grade parking garage. The buildings will be occupied by biotech and life science companies, with commercial space and public amenities on the ground level. Redevelopment is expected to begin in 2022 and is expected to be completed by late 2024.




Proposed Cleanup Actions

The selected cleanup action for the Site meets standards for permanence, protectiveness, implementability, public concerns, compliance with cleanup standards and state and federal laws, and ability to provide compliance monitoring. While nearby sites that may impact this redevelopment are being investigated and remediated, vapor mitigation measures beneath the new structures will be installed to protect human health and the environment. The selected cleanup action for the Site consists of the following:

•Excavating all contaminated soil within the planned redevelopment excavation required for construction of the new buildings to an approximate elevation of at least 7.75 feet (approximately 26 to 51 feet  below ground surface or bgs).

•Hauling the excavated contaminated soil to an off-site facility for treatment and/or disposal.

•Performing compliance monitoring.

Why This Site Matters

The Seattle DOT Mercer Parcels is part of the South Lake Union neighborhood, which is located next to downtown Seattle and bordered on the north by Lake Union. This area has a long history of industrial and commercial activities which caused contamination of the soil and groundwater. Currently, this area is undergoing extensive redevelopment as new buildings are constructed for commercial and residential use. Ecology is working with property owners to clean up contamination present at the Site and other nearby sites to reduce impacts to human health and the environment. 

General Cleanup Process

The Model Toxics Control Act (MTCA; Chapter 70.105D RCW is Washington’s environmental cleanup law). It provides requirements for contaminated site cleanup and sets standards that protect human health and the environment. Ecology enacts the MTCA and oversees cleanups. The MTCA site cleanup process is completed in steps (see graphic below) over a variable timeline.

Legal 5
Public Information 6
Document Title Document Date Document Type
Comment Response Summary Seattle DOT Mercer Parcels 2/28/2022 Responsiveness Summary
Public Presentation Seattle DOT Mercer Dexter Parcels 1/7/2022 Fact Sheet\Public Notices
Seattle DOT Mercer Parcels Factsheet Chinese 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Mercer Parcels Factsheet Spanish 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Mercer Parcels Factsheet 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Mercer Parcels - Public Participation Plan - December 2021 12/2/2021 Public Participation Plan
State Environmental Policy Act 2
Document Title Document Date Document Type
Seattle DOT Mercer Parcels - SEPA Determination - November 2021 11/30/2021 SEPA Documents
Seattle DOT Mercer Parcels - SEPA Checklist - November 2021 11/18/2021 SEPA Documents
Technical Reports 54
Document Title Document Date Document Type
Seattle DOT Mercer Parcels - PPCD Progress Report for January 2024 2/9/2024 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for December 2023 1/9/2024 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for November 2023 12/14/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for October 2023 11/15/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for September 2023 10/4/2023 Progress Report
Seattle DOT Mercer Parcels - Contaminated Media Management Plan 9/29/2023 Site Specific Technical Document - other
Seattle DOT Mercer Parcels - Engineering Design Report 9/27/2023 Engineering Design Report
Seattle DOT Mercer Parcels - PPCD Progress Report for August 2023 9/13/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for July 2023 8/9/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for June 2023 7/7/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for May 2023 6/12/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for April 2023 5/11/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for March 2023 4/12/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for February 2023 3/6/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for January 2023 2/7/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for December 2022 1/5/2023 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for November 2022 12/13/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for October 2022 11/7/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for September 2022 10/11/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for August 2022 9/12/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for July 2022 8/9/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for June 2022 7/12/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for May 2022 6/10/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report for April 2022 5/5/2022 Progress Report
Seattle DOT Mercer Parcels - PPCD Progress Report No.1 - March 2022 4/7/2022 Progress Report
Seattle DOT Mercer Parcels - Final Cleanup Action Plan - February 2022 2/8/2022 Cleanup Action Plan
Seattle DOT Mercer Parcels - Final Focused Feasibility Study 2/3/2022 Feasibility Study
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 7 (Appendix C3 thru F) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 6 (Appendix C2) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 5 (Appendix B thru C1) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 4 (Appendix A3) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 3b (Appendix A2, 2nd half) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 3a (Appendix A2, 1st half) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 2 (Appendix A1) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Final Remedial Investigation Report - Part 1 (text, tables, figures) 2/3/2022 Remedial Investigation Report
Seattle DOT Mercer Parcels - Cleanup Action Plan - PUBLIC REVIEW DRAFT 11/18/2021 Cleanup Action Plan
Seattle DOT Mercer Parcels - Ecology SHA Rank Letter 8/24/2021 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Mercer Parcels - Site Hazard Assessment 8/16/2021 Site Hazard Assessment Report
Seattle DOT Mercer Parcels - Focused Feasibility Study - PUBLIC REVIEW DRAFT 7/13/2021 Feasibility Study
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix D thru F) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix C2 thru C3) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix B thru C1) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix A3) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix A2) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (Appendix A1) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Remedial Investigation Report (text, tables, figures) - PUBLIC REVIEW DRAFT 6/25/2021 Remedial Investigation Report
Seattle DOT Mercer Parcels - Draft RI Review Comments Summary 8/18/2020 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Mercer Parcels - Revised Draft Data Gaps Investigation Work Plan 1/23/2020 Remedial Investigation Work Plan
Seattle DOT Mercer Parcels - SHA Notification Letter 11/22/2019 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Mercer Parcels - Site Investigation Summary Report 10/15/2019 Remedial Investigation Report
Seattle DOT Mercer Parcels - Initial Investigation Field Report 9/24/2018 Initial Investigation Report
Seattle DOT Mercer Parcels - Release Report Letter 6/22/2018 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Mercer Parcels - Phase I ESA 1/25/2018 Site Specific Technical Document - other
Seattle DOT Mercer Parcels - Draft Limited Phase II ESA 6/2/2017 Site Specific Technical Document - other
Voluntary Cleanup Program 2
Document Title Document Date Document Type
Seattle DOT Mercer Parcels - Opinion Letter Draft RI 8/18/2020 VCP Opinion on Remedial Investigation
Seattle DOT Mercer Parcels - VCP Acceptance Letter 1/27/2020 VCP Administrative Document
There may be more documents related to this site. To obtain documents not available electronically, you will need to make a public records request.

Places to see print documents

  • Northwest Regional Office
    15700 Dayton Ave N
    Shoreline, 98133
    Please schedule an appointment to view print documents at this location.

Contaminants 5

Contaminant Type
Soil
Groundwater
Surface Water
Air
Sediment
Bedrock
Metals - Lead C
Non-Halogenated Organics - Benzene C
Non-Halogenated Organics - Petroleum-Diesel C
Non-Halogenated Organics - Petroleum-Gasoline C C
Non-Halogenated Organics - Petroleum-Other B C
S
Suspected
C
Confirmed Above Cleanup Levels
B
Below Cleanup Levels
RA
Remediated-Above
RB
Remediated-Below
R
Remediated
This contaminant list was based on our best information at the time it was entered. It may not reflect current conditions at the site.