SITE INFORMATION AND CORRESPONDENCE_1994-1996

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Wendy L. Cohen -3- 5 May 1994 I have reviewed further HLA's 1 I October 1993 Plume Characterization Investigation Report and sections of PRC Environmental Management, Inc.'s July 1993 and the revised February 1994 Site Investigation Report for the nearby Naval Communication Station. HLA's report states that the concentrations of TPHD in ground water at several locations decreased near Hooper Drive and then increased moving west and southwest of Hooper Drive. The report also states that a nondetect line was apparent for benzene, toluene, ethylbenzene, and xylene [BTEX (samples 49, 50, 41, 42, and 47)] parallel to Hooper Drive and that low concentrations of BTEX appeared southwest of that area (Plate 2, Sample 51). The report concluded that another potential source of petroleum hydrocarbon constituents likely exists on Navy property. The report further states that the presence of chlorinated solvents in ground water in the vicinity of Site 4 appears to present a greater potential threat to ground water quality than the concentrations of TPHD in the area south and west of Hooper Drive. The PRC report states that Site 4 was used for temporary storage of leaking and/or damaged containers from 1972 to 1983, a site investigation has been completed, and DDT-contaminated surficial soil is the key problem at this site. PRC recommended removal of surface soil containing DDT at Site 4. Regarding the petroleum hydrocarbon contamination at Shell, PRC recommended that the Navy request Shell to control and clean up the hydrocarbon plume migrating in ground water beneath the Navy property, and evaluate Shell's monitoring wells for abandonment based on recognition of a confined aquifer and excessive screen lengths. Comments 1. As stated in the Plume Characterization Investigation Report, BTEX was detected at low levels in Sample 51, southwest of Hooper Drive. This is just one sample and the result was not verified. Additional samples should have been taken to confirm these results. 2. The TPHD detected west of Hooper Drive is within the range of TPHD detected east of Hooper Drive. This could be the same plume. 3. Attachment 1 presents the results of soil and ground water sampling around Site 4 at the USN property. The soil samples were obtained from sample locations 17-20. Ground water samples were taken from MWs 3, 4, and 20. The soil sample results show the presence of oil and grease (33-4,800 mg/kg) and pesticides at all four sampling locations, long chain hydrocarbons (130 mg/kg) in sample 19, toluene (0.001 mg/kg) and pentachlorophenol (0.081 mg/kg) in sample 17, and tetrachloroethane in sample 18 (0.003 mg/kg) and sample 20 (0.099 mg/kg). The ground water sample results show nondetectable levels of BTEX, TPH, and oil and grease in MWs 3 and 20. MW 4 contained TPH (1.7 µg/1), oil and grease (3 mg/1), and phenol (26 µg/1). MWs 3 and 20 had 160 and 4 µg/1, respectively, of 1,2-dichloroethene (DCE). MW 3 also had 1,1- dichloroethane; 1,1-DCE; trichloroethylene; tetrachloroethylene; and vinyl chloride. Based on these results, Site 4 does not appear to be the source of petroleum hydrocarbons detected west of Hooper Drive during Shell's Phase III hydropunch investigation. 4. It is not known if the chlorinated hydrocarbon compounds and pesticides being detected in the vicinity of Site 4 are present in the hydropunch investigation area since these chemicals were not analyzed during Shell's investigation. The presence of these compounds in the hydropunch investigation area would suggest that contaminants from Site 4 are migrating towards this area.