Seattle DOT Mercer Parcels
Facility Site ID:
27913
Cleanup Site ID:
14784
Current Status
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.
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 documents' link.
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
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 documents' link.
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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Site Information
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.
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
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.
•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
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.
•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.
Documents 74
Legal 5
Document Title | Document Date | Document Type |
Seattle DOT Mercer Parcels - Prospective Purchaser Consent Decree - FINAL | 2/23/2022 | Consent Decree |
Seattle DOT Mercer Parcels - Prospective Purchaser Consent Decree - PUBLIC REVIEW | 11/18/2021 | Consent Decree |
Seattle DOT Mercer Parcels - Final PLP Status Letter | 7/9/2019 | Final Potentially Liable Person Status Letter |
Seattle DOT Mercer Parcels - Preliminary PLP Letter | 3/26/2019 | Early Notice Letter |
Seattle DOT Mercer Parcels - Early Notice Letter | 10/31/2018 | Early Notice Letter |
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 59
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 Office15700 Dayton Ave NShoreline, 98133Please 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.