SITE INFORMATION AND CORRESPONDENCE

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ICF KAI SLX page 2 The workplan specified one 4-paint composite sample was to be collected to profile the soil for disposal at a Class II landfill. Soil samples were collected on April 26, 1996 from four locations in the vicinity of CS-13 by hand-augering to a depth of 2.5 feet and compositing the soil within each column in the field. The location of CS-13 was identified in the field by marker flags that were left during the original August 1995 sampling. Sample 13D was collected adjacent to CS-13, sample 13A was collected 10 feet to the east, sample 13B was collected 10 feet to the north and sample 13C was collected ten feet to the west of CS-13. . During the profile sampling, it was noted that the sampled soils appeared clean (i.e., no odor or staining) compared to the concentrations detected in August 1995 (TPH-d of 5,500 mg/kg and TPH-o of 11,000 mg/kg). Analysis of the soil samples by method 8015 yielded TPH-o concentrations ranging from 210 to 610 mg/kg; TPH-d was not detected in any of the samples (detection limits ranged from 1 to 20 mg/kg). The laboratory data sheet are attached. Possible explanations for the lower concentrations include the time difference of approximately 9 months between the two sampling events. During this time frame, bioremediation may have reduced concentrations to their current levels. Also, the sampling methods used were different. During the first sampling event, soil samples were collected from discrete intervals by using a split spoon soil sampling device driven with a slide hammer into undisturbed soils. During the profiling event, a composite sample was created which consisted of soil from throughout a 2.5 foot sample interval. We believe that the composited soil samples are more representative of the average hydrocarbon concentrations that should be assessed for potential risks to beneficial water uses compared to the point sample that was previously analyzed and found to have higher concentrations. Note that because no volatile compounds (e.g., BTEX) have been detected in any of the previous soil analyses, there was no risk of losing volatiles during the field soil compositing process. These current TPH-d concentrations fall well below the soil cleanup goals stated above, which ICF Kaiser feels are sufficiently protective of beneficial water uses, and which pose no significant threat to human health or the environment. Based on this new information, we believe no further action is warranted in respect to the stockpiled soil. We therefore recommend that the soil stockpile issue be considered closed.