Fox Avenue
(Former Great Western Chemical) Site

Client: Fox Avenue, LLC
Design and investigation of a significant release of chlorinated solvents. Design and implementation of the remedy using in situ treatment, substrate injection, and vapor extraction, working around an active chemical distribution warehouse.

Overview of Floyd|Snider Contributions

Designed/implemented data gap investigations that identified DNAPL source areas not previously discovered
Vapor intrusion study for multiple occupied on-site and off-site structures located over the contamination plume
Project management of the complex remedial action that included in situ thermal desorption, enhanced reductive dechlorination, and soil vapor extraction
Prime consultant leading agency and client coordination, and project path

Project Summary

Floyd|Snider remediated a significant release of chlorinated solvents from soil and groundwater related to prior storage, handling, and distribution of bulk chlorinated solvents (primarily tetrachloroethylene) and other chemicals associated with the now defunct Great Western Chemical Company.

The Fox Avenue Building Site is an active chemical distribution warehouse in the Duwamish Industrial Corridor of south Seattle. Contamination was once present on-site as dissolved phase in groundwater and dense non-aqueous phase liquid (DNAPL) in soil 65 to 70 feet below ground surface. Remediation was complicated because soil contamination extended beneath an active chemical distribution warehouse and the groundwater plume flowed off-site at concentrations detectable in indoor air in adjacent industrial properties. The plume eventually discharged into the Duwamish Waterway via a series of tidal seeps.

Floyd|Snider remediated a significant release of chlorinated solvents from soil and groundwater related to prior storage, handling, and distribution of bulk chlorinated solvents (primarily tetrachloroethylene) and other chemicals associated with the now defunct Great Western Chemical Company. The Fox Avenue Building Site is an active chemical distribution warehouse in the Duwamish Industrial Corridor of south Seattle. Contamination was once present on-site as dissolved phase in groundwater and dense non-aqueous phase liquid (DNAPL) in soil 65 to 70 feet below ground surface. Remediation was complicated because soil contamination extended beneath an active chemical distribution warehouse and the groundwater plume flowed off-site at concentrations detectable in indoor air in adjacent industrial properties. The plume eventually discharged into the Duwamish Waterway via a series of tidal seeps.

Our Approach

Floyd|Snider designed and implemented an investigation and response strategy to address a significantly contaminated Site in a short period of time.

Within 5 years of an Agreed Order with Ecology, Floyd|Snider identified the source area to ongoing contamination, implemented interim actions for risk reduction, and designed and implemented a Site remedy.

The Floyd|Snider Team investigated and defined DNAPL source areas using a membrane interface probe and initiated an interim action to treat off-site groundwater by injecting a sugar substrate to promote reductive dechlorination of the solvents. A vapor intrusion study was conducted that included collecting samples of sub-slab soil vapor, indoor air, and ambient air. Floyd|Snider then prepared the RI/FS and a final CAP. Floyd|Snider provided oversight on the complex remedy, which included in situ thermal desorption using electrical resistance heating (ERH), continued injection of substrate in the downgradient groundwater plume, and designed a separate soil vapor extraction system to treat a secondary source area. Following completion of ERH in 2013, source area injections of edible oil in the main source area began, and within 3 years achieved greater than 99% reduction in pre-cleanup total volatile organic compound concentrations throughout the majority of the plume.

Project Milestones:

2011. Ecology approves final RI/FS and CAP reports
2013. Completed in situ thermal resistance heating

Floyd|Snider designed and implemented an investigation and response strategy to address a significantly contaminated Site in a short period of time. Within 5 years of an Agreed Order with Ecology, Floyd|Snider identified the source area to ongoing contamination, implemented interim actions for risk reduction, and designed and implemented a Site remedy.

The Floyd|Snider Team investigated and defined DNAPL source areas using a membrane interface probe and initiated an interim action to treat off-site groundwater by injecting a sugar substrate to promote reductive dechlorination of the solvents. A vapor intrusion study was conducted that included collecting samples of sub-slab soil vapor, indoor air, and ambient air. Floyd|Snider then prepared the RI/FS and a final CAP. Floyd|Snider provided oversight on the complex remedy, which included in situ thermal desorption using electrical resistance heating (ERH), continued injection of substrate in the downgradient groundwater plume, and designed a separate soil vapor extraction system to treat a secondary source area. Following completion of ERH in 2013, source area injections of edible oil in the main source area began, and within 3 years achieved greater than 99% reduction in pre-cleanup total volatile organic compound concentrations throughout the majority of the plume.

Project Milestones:

2011. Ecology approves final RI/FS and CAP reports
2013. Completed in situ thermal resistance heating

Project Team

Floyd|Snider
CALIBRE Systems
TRS Group
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