Seatac Development

The results show that groundwater conditions have improved significantly following the operation of the In-Situ Air Sparging and Soil Vapor Extraction (IAS/SVE) System which started last May 2013.

Monitoring Wells (MW) Results

• Overall, the concentrations are trending downward as shown in the graph to the left.
• In December 2014, two wells (MW-07 and MW-09) on the property were above state cleanup levels.
• Only one off-property well that was sampled contained chemicals above cleanup levels (MW-22). Two monitoring wells (MW-15 and 16) had previously detected contaminants above cleanup levels but not sampled for performance monitoring.
• Groundwater monitoring will continue as specified in the cleanup plan.
• Performance Groundwater Monitoring Report - Spring 2016 Semi-annual SEA-TAC Development Site (MasterPark Lot C)

Maps of the wells may be found in the Performance Groundwater Monitoring Report (click on link below).

Next Steps:
In-Situ Air Sparging and Soil Vapor Extraction system will operate for 5 years following the schedule in the Cleanup Action Plan.

SIGNED CONSENT DECREE AND ENGINEERING DESIGN REPORT AVAILABLE

The SeaTac Development Consent Decree was entered in court in July 2012. The signed document is now available for download (see below). The Engineering Design Report (EDR) is also available.  The EDR provides detailed plans and specifications to carry out the preferred cleanup alternative chosen for the site.  The approach to clean up the gasoline contamination in groundwater and soil beneath the site will consist of:

• Injecting air into groundwater below the contamination (air sparging)
• Creating a vacuum in soil above the water table to remove petroleum compounds in contaminated soil (soil vapor extraction)
• Maintaining the asphalt surface in order to prevent contaminated soil from getting in contact with people or from leaching by rainwater
• Maintaining institutional controls on the property that restricts groundwater use and any activities that may interfere with operation of the remediation system at the site.
• Monitoring groundwater for natural attenuation of the plume.

The cleanup is expected to destroy source area contamination and reduce and eventually eliminate groundwater plume contamination.  Click on the link below to download the Engineering Design Report (August 2012).

The SeaTac Development site is located at 16025-16223 International Blvd in SeaTac, Washington. Sea-Tac Investments LLC currently leases the property from ANSCO Properties, LLC and developed it for use as an airport parking lot. Previously, various companies operated businesses there, some of which utilized fuel products and underground storage tanks. Scarsella Bros. Inc. once owned the property and operated a construction yard on the property until the 1970s. This site is not related to the Sea-Tac International Airport or Sea-Tac Ground Water Study.

Gasoline contamination was discovered in 2000 in soil and groundwater on the property. Since 2000, investigations and cleanups were done on the property under Ecology’s Voluntary Cleanup Program. However, gasoline contamination remains in a groundwater aquifer 50-60 feet below ground surface. This contamination extends slightly outside the property boundaries. In 2011, a Report of Investigation/Feasibility Study (RI/FS) and Draft Cleanup Action Plan (DCAP) were completed that: 
    • characterized the contamination 
    • evaluated cleanup alternatives 
    • drafted the plan for remediating the site using the preferred cleanup alternative determined in the Feasibility Study.

In July 2012, a Consent Decree was filed in court to implement the cleanup according to the Cleanup Action Plan (CAP).  In the Consent Decree, the Potentially Liable Parties (PLPs) Sea-Tac Investments LLC, ANSCO Properties, LLC and Scarsella Bros Inc. will clean up the gasoline contamination in groundwater and soil beneath the site as outlined in the CAP.  The cleanup actions to be conducted will involve a combination of injecting air and applying a vacuum in the aquifer to clean it up. It will also involve letting microorganisms clean up the remaining plume. The asphalt pavement above the source area will be maintained. A deed restriction to maintain the asphalt surface and disallow groundwater use at the property is in place as part of the cleanup.  An extensive period of monitoring will be carried out to ensure the cleanup is protective.