Snopac Property

Site Location
The Snopac Property is located at 5055 East Marginal Way S. in Seattle. It is approximately 1.3 acres on the east bank of the Lower Duwamish Waterway, at the head of Slip 1.

Site History

Olympic Lighterage Company used the Site for shipping operations from 1935 to 1940. Pioneer Towing Company occupied the buildings and utilized underground storage tanks (USTs) from 1935 through 1970.  Marine Leasing/Marine Logistics in connection with Marine Power & Equipment utilized the warehouse for marine equipment storage and unlawfully disposed of spent sandblast grit (SBG) on the Site between 1973 and 1988. The contaminated SBG was waste from boat cleaning and maintenance operations. Snopac Products Inc. operated a fish packing facility in the building from 1992 to 2008. In 2008 they relocated the business, leaving the property and warehouse vacant. 5055 Property LLC purchased the property in 2012 and removed the warehouse on the Site in 2019.

Contamination
The Site consists of an uplands area, a shoreface area, and an in-water sediment area. The contamination on this Site is found in the soil, groundwater, and the sediment. The contaminants of concern are: 

• Metals
• Polychlorinated biphenyls 
• Polycyclic aromatic hydrocarbons
• Pentachlorophenol
• Tributyltin Ion
• Total petroleum hydrocarbons

The primary source of contamination at the Site is SBG which contains metals typical of smelter slag. Erosion of this material on the bank has moved contamination into the sediment. 

Interim Action

An Interim Action (partial cleanup) was completed at the Site between December 2020 and January 2021. A shoring wall was installed to 45 feet below ground surface along the western shoreline of the property to support the shoreface. Almost 6,000 tons of SGB-contaminated soil were removed from the landward side of the shoring wall and disposed of offsite. Groundwater monitoring performed after the removal showed reduced concentrations of COCs, indicating the Interim Action was successful in reducing contamination entering the river.

This document is available for public comment from February 24 - April 24, 2025. 

To address the contamination found at the Site, 5055 Properties LLC prepared a Feasibility Study, which evaluated three different cleanup alternatives. The costs and environmental benefits of the alternatives were then compared, leading Ecology to select a cleanup action.

This cleanup action consists of the following activities: 

• Removal: Excavation and offsite disposal of contaminated materials between the shoring wall and the mean higher high water mark (MHHW, dotted blue line on Figure 3). Any wood pilings within the excavation area would be completely removed. Once the cleanup is completed, the slope into Slip 1 will be restored with native plants.
• Monitored Natural Attenuation (MNA): After the removal of the contamination, any remaining contamination would be monitored over time through natural processes. 
• Fencing and signage, called institutional controls in the uplands draft cleanup action plan, will be maintained. These are already at the Site as a part of the previous cleanup work in order to restrict human access and use of the shoreface and tidelands until the removal activities are complete.  
  
  
  

This document is available for public comment from February 24 - April 24, 2025. 

The Snopac Property In-water Area of Slip 1 is a portion of the Lower Reach of the Lower Duwamish Waterway. In-water work will be supervised by the U.S. Environmental Protection Agency (EPA) as part of the cleanup for the Lower Duwamish Waterway. The preferred alternative for the cleanup of Duwamish Waterway in-water cleanup was selected by the EPA based on data summarized in the Lower Duwamish Waterway Feasibility Study  (AECOM 2012) and Lower Duwamish Waterway Record Of Decision  (USEPA 2014).  Information gathered during the RI for this Site was used to refine the selected cleanup actions.

The preferred in-water cleanup action includes measures detailed below: 

• Partial dredge and cap: Dredging and offsite disposal of impacted sediment, followed by the application of an engineered cap with a suitable habitat layer.
• Engineered sediment cap: Placing a layer of clean sand, and possible amendment such as activated carbon, on top of the contaminated sediment, followed by gravel and rock for scour and erosion protection. A habitat layer will be applied to the surface of the cap to reestablish the benthic community. Sediment cap thickness would be 3 feet in subtidal areas and 4 feet in intertidal areas.  
• Enhanced Natural Recovery: The process of placing a thin layer of sand on sediments to help natural recovery.  
• Shoreface/bank excavation and backfill: Excavation of debris and SBG with offsite disposal. Backfill material may consist of clean sand, sand and gravel, or armoring rock to prevent migration of contaminants and to provide a stable bank. 
• Habitat restoration: The restored slope will be flattened for stability and a community of native trees, shrubs, and herbaceous species will be planted to improve shoreline habitat.
• Institutional controls: Non-engineering measures designed to prevent or limit exposure to hazardous substances left in place after the cleanup, and assure the long-term performance of the chosen remedy.

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. 

Why this site matters

The Site is adjacent to the Lower Duwamish Waterway  Superfund Site, which includes a 5-mile stretch of the Duwamish River. The EPA added the LDW Superfund Site  to the Superfund National Priorities List in 2001. Ecology is working to stop or reduce sources of contamination to the LDW Superfund Site, an effort known as “source control,” so that the EPA can proceed with the cleanup of the river sediment.

What happens next?
Ecology will consider all comments received during this public comment period and may make changes to the documents.  If the documents require significant changes, we will hold another public comment period. If no significant changes are made, Ecology will finalize the documents. 

• 5055 Properties LLC, with Ecology oversight, will then create an Engineering Design Report to document engineering concepts and design criteria used for design of the uplands cleanup action. This will provide sufficient information for the development and review of construction plans and specifications. 
• EPA will create a similar document for the design of the in-water work in the Lower Reach of the Superfund site. EPA will also prepare detailed Construction Plans and Specifications and associated quality assurance, permitting/site access, and monitoring plans for the removal and capping action. 
• Next, the remaining upland cleanup work (overseen by Ecology) and the in-water cleanup work (overseen by EPA) will happen at the same time. This portion of the Lower Duwamish Waterway Superfund Site cleanup is projected to occur in 2030.