Problems/Comments

On 15 August 2011, GCI utility installation workers encountered petroleum-contaminated soil and shallow groundwater during trenching operations across Lot 23, within Block 2 of Girdwood Original Townsite. The contamination is believed to have resulted from historical releases; it did not result from a spill during excavation activities. The excavated trench was approximately 75 feet long by 2 feet wide by 3 feet deep when GCI notified the Department of the contamination. Analytical results for soil samples collected from the trench sidewalls (approximately 0.5 to 1 foot below ground surface) showed the following contaminants (all in milligrams per kilogram [mg/kg]): diesel range organics (DRO) 34,000; gasoline range organics (GRO) 6,330; residual range organics (RRO) 158; benzene 6.2; toluene 19.9; ethylbenzene 28.3; and total xylenes 376. Analytical results for water samples collected from the trench excavation showed the following contaminants (all in mg/L): GRO 3.6; DRO 3.14; and benzene 0.00803. Low concentrations of toluene, ethylbenzene, and total xylenes were also detected in the samples. Prevention and Emergency Response Program (PERP) staff advised GCI to dispose of contaminated trench spoils. A total of 17.82 tons of petroleum-contaminated soil were transported to Alaska Soil Recycling (ASR) for thermal treatment and disposal. GCI backfilled the lower part of the trench with trench spoils with low heated headspace readings, and the upper part (above the shallow groundwater table) with clean fill. GCI also hydroseeded the area to restore site vegetation. The proposed underground utility line was re-routed to avoid this contaminated area. This site is determined to be a "Duplicate" of Girdwood Townsite Streets file 2110.38.002. This site will be given "Non-Qualifying" status and future reference will be captured in the Girdwood Townsite Streets file 2110.38.002.

Action Information

Contaminant Information

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