Block 38 West
520 Westlake Ave N, Seattle, WA 98109

Block 38 West Site - street view
Please click on the photo for a larger view


Updated March 2020

Please note: the Northwest Regional Office, the document repository for this Site, is temporarily closed to the public.  Please access documents online through the links below.

Ecology negotiated a legal agreement called an Agreed Order with City Investors IX LLC, the Potentially Liable Person (PLP) for the Block 38 West Cleanup Site (Site). The order requires them to investigate environmental conditions and develop a draft cleanup plan.

Ecology is hosting a public comment period from March 16 - April 14, 2020 to get input on the Agreed Order and other documents for the Site. 

 Agreed Order – requires the PLP to investigate contamination, complete a Remedial Investigation (RI), Feasibility Study (FS) and draft Cleanup Action Plan (dCAP) for the Site. 

 Public Participation Plan – describes how Ecology will inform the community about Site activities and opportunities to be involved in the cleanup process. 

View the fact sheet:
2020 Fact sheet in English
2020 Fact sheet in Spanish
2020 Fact sheet in Chinese

Why this cleanup matters 

The Block 38 West Site 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

Currently, this area is undergoing extensive redevelopment as new buildings are constructed for commercial and residential use. Proposed construction activities at the Site could impact an existing groundwater contaminant plume located nearby.  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. 

Block 38 West Site - aerial view
Please click on the photo for a larger view


Site Location

The Block 38 West Site is located in the South Lake Union neighborhood of Seattle (see figure on page 2). The property known as Block 38 West is generally located at 500-536 Westlake Avenue North, is approximately 1.06 acres in size, and consists of three parcels (Property). 

Site History

Past uses of the Property include a lumber storage yard, a blacksmith shop, warehouse storage, and retail and commercial operations and associated parking.The Property’s structures have been demolished as part of planned
redevelopment of the Property.  The redevelopment includes construction of a multistory mixed-use building with a preliminary design for a 12-story office building above street level and four levels of parking below street level.

An independent cleanup action (without Ecology oversight) is currently ongoing at the Site in connection with redevelopment.


Previous investigations at the Site found the following in soil
and/or groundwater:
•  petroleum hydrocarbons (as diesel-range and oil-range organics)
•  polycyclic aromatic hydrocarbons (PAHs), including naphthalenes and
    carcinogenic PAHs (cPAHs)
•  benzene

 These contaminants were found at levels that exceed allowable standards under the state’s cleanup law, the Model Toxics Control Act (MTCA Chapter 70.015D RCW), and therefore must be addressed during the cleanup action. Cis-1,2-dichloroethene was also found in the groundwater but at concentrations below applicable cleanup levels under MTCA.


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. 

Please click on the photo for a larger view


Map showing site location as King County, WA SITE INFORMATION


View Electronic Documents

Cleanup Site Details Report

Facility Site ID: # 62773

Cleanup Site ID: 15008

Seattle, King County

Status: Awaiting Cleanup   Get definitions of Status terminology

Tena Seeds
Site Manager
(425) 649-7008

Kelsey Ketcheson
Public Involvement Coordinator
(425) 649-7287

Document Repositories:

Northwest Regional Office
3190 160th Ave SE
Bellevue, 98008-5452