Laserfiche WebLink
Waste Management Unit Report -5- 10 September 1991 <br /> DDRW, Tracy <br /> Page 3-14. The Report states that the Building 28 Sump (WMU 6) contained sludges <br /> which had hazardous concentrations of DDT, Heptachlor and 2,4,5-T. The <br /> Report also states that a sample from the base of the excavation of this <br /> sump had a concentration of DDT at 12 milligrams per kilogram (mg/kg) . <br /> The hazardous concentration of DDT is 1.0 mg/kg. The soil samples from <br /> the base of the excavation also had 38 and 45 mg/kg of petroleum <br /> hydrocarbons. These concentrations are above the Practical Quantitation <br /> Limit (PQL) . It is unclear whether these contaminated soils were left in- <br /> place or were removed as part of the cleanup. If these soils were left- <br /> in-place, then the cleanup may be considered incomplete as these <br /> concentrations of waste constituents may pose a threat to water quality. <br /> Page 3-70. The Report states that the UGT from the Building 247 Petroleum Laboratory <br /> (WMU 24) was removed in 1988 and soil samples were collected from the base <br /> of the excavation. One of the samples from the base of the excavation had <br /> hazardous concentrations of DDT (10 mg/kg) . The soil samples from the <br /> base of the excavation also had concentrations of petroleum hydrocarbons <br /> at 9100 and 300 mg/kg. It is unclear whether these contaminated soils <br /> were left in-place or were removed as part of the cleanup. If these soils <br /> were left in-place, then the cleanup may be considered incomplete as these <br /> concentrations of waste constituents may pose a threat to water quality. <br /> Page 4-3. The Report indicates on pages 4-3 to 4-4 that data from the soils gas <br /> investigations have not been an effective method in the investigation of <br /> the WMUs and that volatile organic constituents (VOCs) do not appear to be <br /> present in most of the areas in which the WMUs exist. These conclusions <br /> may be premature because soils gas investigations were not conducted in <br /> several of the WMUs in which it would be anticipated that vapor phase from <br /> wastes disposed of in the WMUs may be present. This concern was discussed <br /> in the comment to Page 2-9. <br /> Page 4-5. The Report states that a risk assessment may be performed for each WMU. <br /> Based on discussion in the text of the Report the risk assessment will <br /> determine the impacts to air, soil and ground water. The impacts to <br /> ground water must be determined through an environmental fate analysis, <br /> such as the Designated Methodology, so that the soil clean-up levels will <br /> be ground water protective. <br /> Page 4-13. The location of the monitor well to be installed in Burn Pit No. 1 <br /> (WMU 7) , as depicted in Figure 4-4, appears to be inside Building 19. The <br /> boring/well should be moved slightly to the east which would still remain <br /> in the central portion of the of the burn pit but would be outside of the <br /> building. <br /> Page 4-15. The location of the soil boring and monitor well in Burn Pit No.2 (WMU 8) , <br /> as depicted in Figure 4-15, should be reversed. The monitor well should <br /> be installed in the northeastern portion of the WMU, if the soil samples <br /> confirm that there is contamination near the ground water table, and <br /> because the ground water flow direction is to the northeast. <br /> Page 4-17. It is unclear why trenching is to be used as an alternative method of <br /> investigation for the Medical Supplies Burial (WMU 10) but is not <br /> recommended for other WMUs. For example, it is unclear why trenching is <br />