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HWAAP-B20
BUILDING 101-41 CATCHMENT PIT
SITE DESCRIPTION
HWAAP-B20 consists of three inactive unlined surface impoundments, two steel settling tanks, and one trench located southwest of Building 101-41.  The impoundments are interconnected and range from 1,300 to 2,700 square feet in area and between 6 and 10 feet deep. Associated with them is a trench that runs west from the tank location. Two steel tanks placed in tandem between Building 101-41 and the impoundments allowed for settling of solids prior to discharge to the impoundments. The impoundments and trench are partially filled with windblown sand. Piles of dredged soils are located on the sides of the impoundment. This impoundment operated from 1940 to the early 1970's and received large amounts of waste water containing TNT and RDX.
Remedial investigation work completed in 1994 included surface soil and hand auger sampling, and cone penetrometer (CPT) sampling. Seven surface soil samples, seven hand auger samples and four CPT soil samples were collected and analyzed for explosives and metals. Visible evidence of TNT stained soils were observed in the impoundments. Elevated concentrations of RDX (310 mg/kg), 1,3,5-TNB (87 mg/kg), 2,4,6-TNT (20,000 mg/kg), 2-Amino-DNT (20 mg/kg), and 2,4-DNT (18 mg/kg) were detected in soil exceeding the remediation criteria. None of the metals were detected at levels exceeding the soil remediation criteria. The site was bioremediated under a pilot study of windrow composting. A total of 2,500 cubic yards from B-20, B-32 and I-15 was treated using various recipes in 1997.
In 1997, TCE was discovered in groundwater. In 1999, additional soil gas surveys and subsurface sampling were conducted to delineate TCE in soil. Four passive vapor extraction wells were installed in 1999 and are still operating. An additional groundwater monitoring well was installed in 2002 downgradient of the site. The groundwater sample results from the new well show that concentrations of TCE decrease downgradient.
 Aerial Photo (black & white --127KB)
PROPOSED PLAN
A Closure Decision Document  was approved by the NDEP in July 2009.
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Aerial Photo