Problems/Comments

Notification of a potential leaking underground storage tank (UST) was sent to ADEC. The source of contamination was attributed to over-filling of the UST and a leak in the delivery piping connections. Field activities occurred in August and September of 1996 following the notification. Diesel range organics (DRO), gasoline range organics (GRO), and BTEX (benzene, toluene, ethylbenzene, and total xylenes) concentration above ADEC cleanup levels (CULs), were detected in subsurface soils samples from the UST excavation. Two surface soil samples contained DRO concentrations of 1,150 milligrams per kilogram (mg/kg) and 1,760 mg/kg, which exceed the ADEC Method Two CUL of 250 mg/kg for under 40-inch zone migration to groundwater. One surface soil sample contained a GRO concentration of 609 mg/kg and a BTEX concentration of 15.8 mg/kg, which exceeded the applicable ADEC CULs of 300 mg/kg and 15 mg/kg, respectively. The excavation was backfilled with the DRO, GRO, and BTEX contaminated soils. Potassium nitrate and potassium phosphate were added to the backfilled soils to promote natural biodegradation. August 2008-test pit excavation activities occurred at the former location of UST. Two test pits (TP1 and TP2) were excavated. One subsurface soil sample was collected at TP1, located southeast of the Site, contained a DRO concentration of 972 mg/kg, which exceeds the ADEC Method Two CUL of 250 mg/kg for under 40-inch zone migration to groundwater. April 25 through May 1, 2022- Field activities occurred. Four soil borings, were installed and four monitoring wells were installed and a monitoring well survey was conducted. The utility locates were conducted by Logic Geophysics and Analytics, LLC (LGA); the drilling was conducted by Discovery Drilling, Inc. (Discovery); the monitoring well survey was conducted by Coastal Surveyors, LLC; and the analytical testing was conducted by SGS North America, Inc. of Anchorage, Alaska (SGS). LGA, Discovery, and SGS were subcontracted to UMIAQ Environmental, and Coastal Surveyors were contracted to the BBB. Site photographs taken during field activities are provided in Appendix A and copies of the field notes and logs are provided in Appendix B. Four soil borings, designated Borings B1 through B4, were advanced and completed as groundwater monitoring wells MW1 through MW4, respectively. Eight soil samples (two from each boring) and one field duplicate sample were analyzed. Each of the target analytes were not detected or were detected at concentrations less than the most stringent applicable ADEC CUL. During the April 2022 drilling activities, groundwater was encountered at approximately 16- 18 feet bgs at the site. Depth to groundwater ranged from 15.45 to 18.58 feet below top of casing (btoc) groundwater flow direction is generally toward the southwest. It is thought that groundwater flow is not tidally influenced. Four groundwater samples (Wells MW1 through MW4) and one field duplicate sample were analyzed. Each of the target analytes were either not detected or were detected at concentrations less than the applicable ADEC CUL.

Action Information

Contaminant Information

Control Type

Requirements

No associated sites were found.