SITE INFORMATION AND CORRESPONDENCE

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San Joaquin County Public Health Services A91701 April 16, 1996 Page 2 laboratory analysis a soil sample which registered above 75 ppm during field screening with the PID. Our field geologist recorded in his field notes that the background reading from a representative soil screening bag registered 12.2 ppm. In view of the fact that the PID is a tool for selection of samples for laboratory analysis and is not suitable for quantitative assessment of site soils, and considering the range of PID values measured for site soil, the bias introduced by a background reading of 12.2 ppm is insufficient for us to reevaluate our decisions as to which samples to submit for laboratory analysis. Furthermore the bias is on the "high side", so it would have caused us to over-estimate the amount of organic vapors in the samples and select more samples than necessary for laboratory analysis. 3. '7n addition, during boring of B-1, PHS/EHD staff noted a diesel odor at approximately 35 feet below surface grade (BSG) and suggested the boring be advanced an additional S feet or to clean soil for the purpose of obtaining lateral and vertical definition potentially avoiding remobilization. This recommendation was ignored by the TLI field geologist." Twining's field geologist have been trained to abide by the work scope as outlined in the approved work plan unless evidence exists to warrant additional work. They must obtain field indications that soil contamination extends beyond the planned drilling depth before they will commit to expending additional time, materials and the client's money. Our field geologist did not observe soil staining or odors indicative of soil contaminated with diesel in the sample recovered from 35 feet BSG. He called his supervisor and discussed the PHS/EHD staff suggestion, and the observed data from soil samples collected in soil boring B-1. A joint decision was made that the field indications did not warrant extending soil boring B-1 beyond its planned depth of 35 feet. 4. '7n each soil boring HA 7, 8 AND 10 all site workers from TLI and PHS/EHD observed what appeared to be nonnative soil at 0 to S feet BSG." Wining's field geologist noted that the asphalt and base rock appeared to be unusually thick (approximately 1.5 feet) and that pea gravel (i.e., fill) extended to approximately 4.5 feet BSG. The samples he collected from soil borings HA-7, HA-8, and HA-10 were composed of a dark olive-brown silty sand. The field geologist judged this material to be almost identical to samples collected in soil boring B-8 at 10 feet BSG. The field geologist felt these samples collected at the bottom of soil borings HA-7, HA-8, and HA-10 were therefore native soil. The field geologist does not recall the PHS/EHD staff examining the samples. The driller recalls the PHS/EHD staff examining drill cuttings from the auger flights. The samples collected from soil borings HA-7, HA-8, and HA-10 have since been recovered from the laboratory archives and reexamined by Twining's Environmental Division Manager, a California Registered Geologist and Certified Engineering Geologist. In his opinion, the samples collected from HA-7, HA-8, and HA-10 are consistent with native soil and do not appear to be fill. 5. In reference to the telephone conversation between the PHS/EHD staff and Mr. Ken Jones of Twining. Mr. Jones recalls the conversation vividly due to the rude and abusive manner of the PHS/EHD staff. The PHS/EHD staff told Mr. Jones we were "stupid" and