Commenting open: January 14, 2021 12:00AM PT - February 12, 2021 11:59PM PT.
Tac-Sea Motel Periodic Review
Ecology invites you to review and comment on the periodic review for the Tac Sea Motel Site located at 17024 Pacific Hwy, Seatac, WA 98188.
The Tac Sea Motel Site is located near the north end of Sea-Tac International Airport. The former building was originally constructed as a strip mall in 1953. Two dry cleaners and a printer successively occupied one of the units, between approximately 1953 and the early 1980s, after which the building was converted to a motel. The property is currently being operated as a paid parking lot that opened in 1998.
The former dry cleaning facility left soil and groundwater underlying the Site contaminated with chlorinated solvents and petroleum hydrocarbons. Remediation activities occurred between 1998 and 2011, which included soil excavation and a groundwater treatment system using Air-Sparging with Soil Vapor Extraction (AS/SVE).
A periodic review is conducted every five years after a cleanup action when institutional controls are used as part of the remedy, as required by the Model Toxics Control Act (MTCA). The purpose of the periodic review is to evaluate current site conditions and to ensure continued protection of human health and the environment.
The Periodic Review concluded the following:
Tetrachloroethene (PCE) concentrations in groundwater remain asymptotic and have been less than 10 micrograms per liter (μg/L) for over 10 years. Occasionally, PCE concentrations dip below the state cleanup level (MTCA Method A) of 5 μg/L. Ecology determined in 2013 that the Air-Sparging with Soil Vapor Extraction (AS/SVE) remediation system achieved its maximum cleanup function, and that additional cleanup treatment would be cost disproportionate to the benefits.
The groundwater plume has not been delineated to the west of the property (down gradient). It was reported to Ecology that the west-adjoining property owner did not grant access for sampling. PCE concentrations downgradient of the property are likely lower than in monitoring wells MWA and MWC, given the significant reduction in PCE as a result of the AS/SVE remediation system.
No drinking water wells are likely to be impacted.
The cleanup actions completed at the Site appear to be protective of human health and the environment at this time. Groundwater monitoring should continue so that PCE concentrations continue to be evaluated over time.
Additional details can be found in the 2020 Periodic Review report.
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