SITE INFORMATION AND CORRESPONDENCE_1992

Home Browse Search

Sharpe -UST 2 Fifteen tanks from Table 1-2, which are listed as having no analytical results and/or need additional analysis to determine potential threat to water quality include: Tank Nos. 3, 8, 17, 21, 25, 35, 36, 37, 45, 48, 58, 71, 72, 73, and 74. I would agree with the no further action at Tank Area A, UST 2 and 75, as recommended by ESE in this PAR however, I do not agree with the conclusions for no further action in areas of confirmed ground water impact and in areas of high concentrations of contaminants found in the soils associated with the underground tanks investigated. Specifically, in Area D, UST 27, a black oily residue was found during the drilling of soil boring 27A which lead to shutting down the drilling due to excessive hydrocarbon vapors in the work space. Concentrations of PCB's at 90.0 pg/L were confirmed in MW-427A ground water along with 140 pg/L TCE and 160 pg/L chromium, in association with this tank. In Area M monitoring well MW-474A shows concentrations of 1,800 pg/L TCE, 220 pg/L DCE, 20. 1 pg/L arsenic and 12.0 pg/L PCB's in the shallow ground water. ESE recommends no further action in these locations based on the statement that this contamination should be controlled and remediated by the existing extraction wells. This contamination would have to drawn approximately 275 feet in Area D and approximately 600 feet in Area M to reach the active extraction point (from the ground water gradient map provided for third quarter 1991) , which is unacceptable. A more localized cleanup effort needs to be applied in these areas in addition to better definition of the contaminant plumes and contaminated soils. Also current remediation does not provide removal of PCB's or heavy metals. Additionally, three areas identified in this report still require further monitoring of the ground water quality. Specifically, in Area E, USTs 15, 18 and 18A, showed high levels of diesel contamination in soil borings adjacent to each of these tanks at depths of 10 to 15 ft-bgs. Monitoring well MW-471A was installed and analysis of the ground water did not detect contamination. In Area F, 210 ppm diesel was encountered in the soil sample retrieved during excavation of UST 5, monitoring well MW 469-A was installed and analysis of the ground water did not detect contamination. In Area H, 2070 ppm diesel was encountered in soils adjacent to tank #34. The soil boring was completed as a monitoring well , MW 470-A, and analysis of the ground water did not detect contamination. Areas E, F, and H already have at least one monitoring well that each need to continue to be sampled quarterly, at a minimum, for analysis of dissolved hydrocarbon components. Confirmation ground water sampling is recommended at this time in order to facilitate identification of confirmed source areas for development of the final remedial plan for the entire site. Samples must be analyzed using EPA Method 602, 624, or 8260 to achieve a detection limit of 0.5ppb. The USATHAMA detection limit of 2.85 ppb for benzene is unacceptable when the water quality goal for benzene is 1 ppb. In Area E additional monitoring wells are needed to better define the water table gradient and confirm no impact from soil contamination associated with tank 15 which also showed elevated levels of diesel at 15 ft-bgs. Also in Area E, I strongly recommend the removal of the concrete pad located at approximately 10 ft-bgs in association with USTs 18 and 18A with verification soil samples collected to verify concentrations of hydrocarbon remaining in the ground. Additionally, water level measurements and hydrograph construction would be valuable information to include in the future to evaluate responses of ground water to soil contamination problems. Analysis and recommendations for remedial actions in association with surficial lead contamination was inappropriately presented in the underground storage tank Problem Assessment Report as this contamination was not likely caused by an underground tank system. ESE considers that only concentrations exceeding 500 ppm lead are significant.