SITE INFORMATION AND CORRESPONDENCE

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Captain Kenneth Koop - 2 - 12 September 2002 CARNG Facility- Stockton 4. The PA/SI Report recommended further investigation of the drainage ditch in the Combined Support and Maintenance Shop (CSMS),but no sampling is proposed in the Work Plan. Discrete sampling of surface and shallow subsurface soil in the drainage ditch should be added to the Work Plan. At a minimum samples should be analyzed for petroleum hydrocarbons and metals. The PA/SI Report recommended only petroleum hydrocarbons and zinc,but samples should be analyzed for a full-suite of metals. The previous metals results were from composite samples, so zinc may not be the only metal of concern. 5. The investigation of the uplifted areas does not include sampling. While it would be impossible to select the contaminants of concern in advance of uncovering the source of the uplift, the Work Plan should have a contingency for sampling any suspect soils/materials that are excavated. A contingency for sampling the uplifted areas should be added to the Work Plan. The plan should include contacting the CVRWQCB if potential soil contamination or potential hazardous materials are uncovered. 6. During the PA/SI, soil samples were collected beneath the sand blasting area(Boring B11) and former waste storage area(Boring B10). Even though these areas were potential surface release sites, soil samples were collected at depths of 5 feet below the sand blasting area and 10 feet below the waste storage area. The potential metals contamination associated with sand blasting area is unlikely to migrate far vertically and a surface sample (or sample from just below the pavement if the area is completely paved) should have been collected along with the 5-foot soil sample to assess whether any surface contamination is present. Please collect a surface soil or sample just below the pavement and analyze it for metals to complete assessment of the sandblasting area. Similarly, contamination caused by leaks from the waste storage area are more likely to affect the near-surface soils and some petroleum hydrocarbon contamination was detected at a depth of 10 feet. Concentrations of petroleum hydrocarbons may be much higher in the near-surface soils. At a minimum, soil samples should be collected from the surface and 5 feet bgs to characterize this potential source area. Samples should be analyzed for petroleum hydrocarbons, SVOCs, and metals. VOCs do not appear to be a concern as none were detected in the soil vapor sample collected in this area during the PA/SI. Specific Comments 1. Page 9, Section 3.5: Photographs of all soils and materials excavated from the uplift areas should be taken. Include photodocumentation as one of the activities that will be conducted during excavation of the uplift areas. 2. Table 2: The analytical methods listed in this table contain many erroneous method numbers. For example, the table indicates you will be using EPA Methods 8260, 8261, 8262, 8263, and 8264 to analyze for oxygenates that may be present in soil samples collected from Boring B28. EPA Method 8260 is the correct method for oxygenates. These erroneous method numbers should be corrected.