Problems/Comments

The former military motor pool building was located approximately 1200 feet northwest from the runway. All that remains are the concrete slab and what appears to be a drywell that is filled with rainwater/groundwater. NVY-BG-001 is a former motor repair shop feature identified within the Navy Area during the historical geospatial analysis (HGA) was identified from as-built construction sheet numbers 9 and 10 of 13, dated 24 November 1944, sized at 40 feet by 100 feet. It was also visible in aerial imagery from 1951 to present. The feature was assessed in 2015 as part of the Phase I RI and was identified as a concrete pad with a vehicle service pit (trench drains) located on the west end. The feature was recommended for further investigation based on the feature type and potential for HTRW. The investigation at NVY-BG-001 was conducted in accordance with the Work Plan. Field screening and analytical results show the presence of primarily petroleum contamination in the soil in around and under the concrete pad of the former building footprint (Figures M36-4 through M36-6). UVOST screening identified a petroleum plume in soil at a depth of 0 to 6 feet bgs (roughly 94-100 feet NAVD88) except beneath the vehicle service pits where fuel signatures were slightly deeper. All DRO and RRO exceedances in soil have been successfully delineated both vertically and laterally. The estimated volume of petroleum impacted soil is estimated at 550 cubic yards. The VOCs of 1,2,4-trimethylbenzne, carbon tetrachloride, and hexachlorobutadiene are not vertically delineated in soil at boring location 056. At boring location 053, the VOC 1,2,4-trimethylbenzene in soil is also not vertically delineated. These VOC are laterally delineated. All PAH exceedances in soil have been successfully delineated both laterally and vertically and are collocated with petroleum contamination. A total of nine monitoring wells were installed at NVY-BG-001. In the source well MW-010, the VOCs 1,2,4-trimethylbenzene (0.055 mg/L), 1,2-dichloroethane (0.00023 mg/L), 1,3,5-trimethylbenzene (0.024 mg/L), ethylbenzene (0.063 mg/L), trichloroethene (0.0025 mg/L), and vinyl chloride (0.00018 mg/L) and the PAH naphthalene (0.0036 mg/L) were detected in the groundwater above screening levels. Eight of the wells were used to successfully delineate the groundwater plume in and around the impacted source well MW-010. Contamination observed in MW-010 has been successfully delineated. The estimated aerial extent of impacted groundwater is 3,000 square feet. Groundwater was measured flowing to the southwest across the site. The analytical detections from the surface water sample collected were below established screening levels. The calculated TAH and TAqH levels for surface water were reported below established screening levels. With the exception of benzo(a)pyrene and carbon disulfide all other analytical detections in the sediment sample were below screening levels. The CSM for NVY-BG-001 is consistent with the site-wide CSM in Section 4.7 in that all media are present. However, surface water and sediment do not appear to be a transport mechanism nor an exposure risk. The presence of DRO, RRO, and VOCs in soil, VOCs in groundwater (including TCE), and PAHs in sediment warrants the inclusion of NVY-BG-001 in the baseline risk assessment to be conducted for Atka.

Action Information

Contaminant Information

Control Type

Requirements

No associated sites were found.