Facility Site ID: 81735 Cleanup Site ID: 14785

Current Status

Current view of Site looking west from Dexter Ave N.
Current view of Site looking west from Dexter Ave N.
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 Mercer Parcels 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 Dexter Parcel 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 the RI appendices, please click 'View Electronic Documents' link to right. 

Final Feasibility Study (FS) – 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

Aerial view of Seattle DOT Dexter Parcel site
Aerial view of Seattle DOT Dexter Parcel site
The Seattle DOT Dexter Parcel Site is generally located at 615 Dexter Avenue North (Property) in the South Lake Union neighborhood of Seattle.  The Property is 0.56 acres and bounded to the north by Roy St, to the south by an alley, to the east by Dexter Ave N, and to the west by Aurora Ave North. Contamination at the Site is present on a portion of the Property and extends into an adjacent alley.

Site History
Private residences existed on the Property until the early 20th century.  In the 1920s, a building was constructed on the southern portion of the Property, and later expanded to the north and east in the 1940s. Various commercial and light industrial businesses occupied the building, including sandpaper, hardwood flooring and woodworking companies, a coated wall board manufacturer, a plastic mixing and storage facility, and a restaurant. Most recently, a copier sales and service business occupied the building. A fueling and service station also operated on the Property during the 1930s and 1940s. 

In 2005, a fire destroyed a portion of the main building.  A parking lot replaced the damaged structure. 

Future Property Use

Image of proposed redevelopment.  Credit: Alexandria Real Estate Equities, Inc.
Image of proposed redevelopment. Credit: Alexandria Real Estate Equities, Inc.
The Property is planned to be redeveloped with an 18-story tower and a below-grade parking garage that will encompass the entire footprint of the Property. Two levels of below-grade parking are planned. The building will be a multi-family residential tower and will include a mix of units including market rate and income-restricted units ranging from 60 to 85 percent Area Median Income. Redevelopment is expected to begin in 2023 and is expected to be completed by 2024.








Contamination

Site map. Petroleum hydrocarbons in soil is in solid red and in groundwater in red lines.  Planned excavation area is within the dashed purple lines.  Monitored natural attenuation is in blue. Planned treatment injection locations are in yellow and black
Site map. Petroleum hydrocarbons in soil is in solid red and in groundwater in red lines. Planned excavation area is within the dashed purple lines. Monitored natural attenuation is in blue. Planned treatment injection locations are in yellow and black
Investigations at the Site found the following contaminants in soil and/or groundwater:

•Gasoline-range petroleum hydrocarbons

•Diesel-range petroleum hydrocarbons

•Benzene

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.


Proposed Cleanup Actions

The FS developed three cleanup alternatives that were evaluated for the Site based on permanence, effectiveness, protectiveness, implementability, short- and long-term risk, public concerns, and cost. From that evaluation, a preferred alternative was identified and developed into a draft CAP. The preferred alternative consists of the following actions to clean up the contaminated areas of the Site:

•Excavating contaminated soil and groundwater within the redevelopment excavation area on the Property and transporting it off-site for treatment and/or disposal.

•Injecting oxygen-release compound (ORC®) into the contaminated area within the adjacent alley to enhance in situ bioremediation processes.

•Implementing monitored natural attenuation for remaining contamination in the alley and for any residual contaminated groundwater that may remain on the Property below the planned redevelopment excavation.

•Installing a vapor barrier to protect occupants of the new building from exposures to remaining contamination until concentrations decrease to protective levels.

•Maintaining a protective cap over remaining contamination at the Site.

•Implementing institutional controls to maintain protective barriers and place restrictions on land use to prevent exposures to remaining contamination until concentrations decrease to protective levels.

•Performing compliance monitoring and maintenance.

The draft CAP also includes contingency actions that would be implemented if additional contamination is discovered beneath the existing building following its removal, and to facilitate more rapid remediation of contaminated groundwater in the alley if monitored trends indicate that full compliance would not be met within the estimated restoration time frame. Implementation of this cleanup action will address the cleanup action objectives for the Site.

Why This Site Matters

The Seattle DOT Dexter Parcel 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 4
Public Information 6
Document Title Document Date Document Type
Response Summary Seattle DOT Dexter Parcel 2/28/2022 Responsiveness Summary
Public Presentation Seattle DOT Mercer Dexter Parcels 1/7/2022 Fact Sheet\Public Notices
Seattle DOT Dexter Parcel Factsheet Spanish 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Dexter Parcel Factsheet Chinese 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Dexter Parcel Factsheet 2021 12/2/2021 Fact Sheet\Public Notices
Seattle DOT Dexter Parcel - Public Participation Plan - December 2021 12/2/2021 Public Participation Plan
State Environmental Policy Act 2
Document Title Document Date Document Type
Seattle DOT Dexter Parcel - SEPA Determination - November 2021 11/30/2021 SEPA Documents
Seattle DOT Dexter Parcel - SEPA Checklist - November 2021 11/18/2021 SEPA Documents
Technical Reports 44
Document Title Document Date Document Type
Seattle DOT Dexter Parcel - PPCD Progress Report - January 2024 2/15/2024 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - December 2023 1/8/2024 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - November 2023 12/7/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - October 2023 11/6/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - September 2023 10/4/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - August 2023 9/1/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - July 2023 8/1/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - June 2023 7/6/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - May 2023 6/6/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - April 2023 5/1/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - March 2023 4/3/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - February 2023 3/2/2023 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - December 2022 1/3/2023 Progress Report
Seattle DOT Dexter Parcel - Progress Report - November 2022 12/2/2022 Progress Report
Seattle DOT Dexter Parcel - Pre-Remedial Design Investigation Work Plan 11/11/2022 Site Specific Technical Document - other
Seattle DOT Dexter Parcel - PPCD Progress Report - October 2022 11/4/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - September 2022 10/3/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - August 2022 9/2/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - July 2022 8/1/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - June 2022 7/7/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - May 2022 6/14/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report - April 2022 5/9/2022 Progress Report
Seattle DOT Dexter Parcel - PPCD Progress Report No. 1 - March 2022 4/7/2022 Progress Report
Seattle DOT Dexter Parcel - Transfer of Interest to SLP 615 Dexter LLC 2/23/2022 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - Final Cleanup Action Plan - February 2022 2/8/2022 Cleanup Action Plan
Seattle DOT Dexter Parcel - PPCD Progress Report - January 2023 2/3/2022 Progress Report
Seattle DOT Dexter Parcel - Final Feasibility Study 2/3/2022 Feasibility Study
Seattle DOT Dexter Parcel - Final Remedial Investigation Report - Part 2 (appendices) 2/3/2022 Remedial Investigation Report
Seattle DOT Dexter Parcel - Final Remedial Investigation Report - Part 1 (text, tables, figures) 2/3/2022 Remedial Investigation Report
Seattle DOT Dexter Parcel - Cleanup Action Plan - PUBLIC REVIEW DRAFT 11/18/2021 Cleanup Action Plan
Seattle DOT Dexter Parcel - Feasibility Study - PUBLIC REVIEW DRAFT 11/2/2021 Feasibility Study
Seattle DOT Dexter Parcel - Ecology SHA Rank Letter 8/24/2021 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - Site Hazard Assessment 8/16/2021 Site Hazard Assessment Report
Seattle DOT Dexter Parcel - Remedial Investigation Report (appendices) - PUBLIC REVIEW DRAFT 7/9/2021 Remedial Investigation Report
Seattle DOT Dexter Parcel - Remedial Investigation Report (text, tables, figures) - PUBLIC REVIEW DRAFT 7/9/2021 Remedial Investigation Report
Seattle DOT Dexter Parcel - PPLP Response 3/13/2020 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - PPLP Extension Request 2/14/2020 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - Revised Draft Data Gaps Investigation Work Plan 1/23/2020 Remedial Investigation Work Plan
Seattle DOT Dexter Parcel - SHA Notification Letter 11/22/2019 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - Site Investigation Summary Report 10/15/2019 Remedial Investigation Report
Seattle DOT Dexter Parcel - Initial Investigation Field Report 9/24/2018 Initial Investigation Report
Seattle DOT Dexter Parcel - Release Report Letter 6/22/2018 Site Specific Administrative Document - other (Administrative correspondence)
Seattle DOT Dexter Parcel - Phase I ESA 1/25/2018 Site Specific Technical Document - other
Seattle DOT Dexter Parcel - Draft Limited Phase II ESA 6/8/2017 Site Specific Technical Document - other
Voluntary Cleanup Program 3
Document Title Document Date Document Type
Seattle DOT Dexter Parcel—NW3257 VCP Opinion on Draft Feasibility Study 11/9/2021 VCP Opinion on Site Cleanup – Other
Seattle DOT Dexter Parcel - Opinion Letter on Draft Remedial Investigation Report 8/28/2020 VCP Opinion on Remedial Investigation
Seattle DOT Dexter Parcel—NW3257 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 3

Contaminant Type
Soil
Groundwater
Surface Water
Air
Sediment
Bedrock
Non-Halogenated Organics - Benzene C
Non-Halogenated Organics - Petroleum-Diesel C
Non-Halogenated Organics - Petroleum-Gasoline C 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.