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T] KLE]NFFIDFR soils may become impacted due to the petroleum constituents detected in groundwater at the MW -4 location near first encountered groundwater including zones in which groundwater may fluctuate seasonally. 11. One four point composite sample was analyzed from an approximately 75 yard stockpile located at the subject site. Based on the analytical results it appears diesel and motor oil impacted soil remain in this stockpile 6.2 RECOMMENDATIONS 1. Kleinfelder recommends shallow excavation of petroleum impacted soil in the washdown area followed by confirmation soil sampling. The approximately 75 yard soil stockpile located at the site should be disposed of according to local and federal regulations. Kleinfelder recommends removal of the excavated washdown area soil and the existing stockpile in a single disposal event. 2. Previous remedial activities (excavation of petroleum impacted soil) has occurred at the subject site in the former UST area and a "No Further Action" letter was obtained from the county. Field observations and soil sampling results in the vicinity of the UST shows that petroleum impacted soil remains at approximately depth of 25 to 45 feet in the eastern portion of the southern excavation. However, soil sampling results show a marked decrease in petroleum constituents at 40 feet bgs and none detected results at 50 feet bgs. Groundwater samples from monitoring wells in this area also were reported as non -detect for the requested petroleum constituents including oxygenates from first encountered grow-idwater. Based on these findings and the previous "No Further Action" letter by the county and that the county was aware contamination remained at approximately 30 feet bgs (UST area), Kleinfelder does not recommend further remedial efforts in this area. j. Kleinfelder recommends that a copy of this report should be submitted to San Joaquin County Public Health Services Department, Environmental Health Division (PHSIEHD) and the State of California, Central Valley Regional Water Quality Control Board (RWQCB) for their review and comment. 4. The equipment decontamination rinseate, purge water and drilling returns (soil) currently stored on-site should be properly disposed of by the Client. Kleinfelder can assist the Client in that disposal at an additional charge if requested. This report, and the conclusions and recommendations presented in this Executive Summary, are subject to the "Limitations" presented in Chapter 7 of this report. Any other party (other than The San Joaquin County Mosquito & Vector Control District or regulatory agencies having enforcement jurisdiction for this site) who would like to use this report shall notify Kleinfelder, Inc. of such intended use by executing the "Application for Authorization to Use" which is included as an appendix to this report. 36274 / ST03R1919 Page IS of 19 3004 Kleinfelder, Inc. January 3, 2004