SITE INFORMATION AND CORRESPONDENCE_FILE 1

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• i LLEEDSHILL•HERKENHOFF, INC. Thomas D. Peltier February 2, 1990 Page 2 On January 15, 1990, LH submitted the findings and recommendations of this sampling program to the County for review and approval. In a subsequent phone conversation, LH learned that the County was referring the approval to the Central Valley Regional Water Quality Control Board (RWQCB), the lead agency for this site. Therefore, this letter presents the findings and recommendations of this program and requests written concurrence. BACKGROUND As reported in a City of Stockton Fire Prevention Bureau Tank Removal Permit, in December 1978, two 7500 gallon gasoline tanks were removed from the site at 102 South Wilson Way. This permit showed the south east corner of the former tank excavation to be approximately 75 feet east of Wilson Way and 45 feet south of Market Street. After removal of the tanks, the excavation was backfilled to grade and paved. In April 1988 a site investigation was conducted by others to determine the presence or absence of petroleum hydrocarbon soil contamination at this site. A soil boring was installed by others in the center of the previous excavation. The boring TB1 was drilled to a total depth of 40 feet with soil samples collected at depths of 2 feet, 5 feet, and at 5-foot intervals thereafter. With the aid of an on-site organic vapor detector, samples collected from 2, 10 and 15 feet were selected for laboratory analysis. These samples were analyzed for total petroleum hydrocarbon (TPH) as both gasoline and diesel. These results are summarized on Table 1 and the laboratory certificates are also enclosed. The representative soil samples tested by others showed the near surface presence of residual TPH as gasoline from a depth of 2 to 3 feet. All other soil analysis from boring TB1 showed non detectable levels of TPH as both gasoline and diesel. In an effort to remediate the site, based on this analytical data and the original tank removal permit, soils i were excavated to a depth of approximately 4 feet and stockpiled on site. The existing excavation and approximately 55 cubic yards of stockpiled soil are the results of this remediation attempt by others. CONCLUSION AND RECOMMENDATIONS As presented on Table 1, the residual petroleum hydrocarbons in the existing soil stockpile and the barrels containing soil are almost all below minimum detection limits. These extremely low residual levels are well below concentrations which would pose a threat to groundwater resources in the area. Soil samples from the excavation below a depth of four feet also show non detectable levels of petroleum hydrocarbons. LH; therefore, recommends and requests RWQCB approval for disposal of this on site