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• feet below grade Well TB6 is located south of well TB4 and extends to a depth of 25 feet below grade The well is screened from total depth to 5 feet below grade and will be used to complement nearby well MW5 in a remediation program Further details on well construction are included in the drilling logs attached as Appendix A Borings TB3, TB13, and TB14 were installed 15 feet below grade, and are located in the pump dispenser island area The locations of these bonngs were selected with your assistance, based on your observations of the piping removal investigation in November 1994 Boring TB3 is located north of the cashier's booth near a fiberglass pipe that was found during excavation of the site Each of the borings were installed with a low clearance hollow stem auger drilling ng Results of soil analyses indicate that the samples from well TB4 had the highest hydrocarbon concentrations with a maximum of 4,100 mg/kg TPH detected at 10 feet below grade Each of the samples from this boring contained greater than 1,000 mg/kg except for sample TB4-40 Soil samples from well TB6 contained a maximum concentration of 100 mg/kg at 15 feet below grade The deeper samples contained 62 and 55 mg/kg TPH (at 20 and 25 feet below grade, respectively) Samples from borings TB13 and TB14 did not contain detectable concentrations of hydrocarbon, samples form TB3 contained up to 760 mg/kg TPH The laboratory data is presented as Appendix B GROUNDWATER MONITORING AND SAMPLE COLLECTION The last groundwater sampling event was conducted on September 7, 1994 The results of this monitoring event were reported in the last monitoring report dated October 21, 1994 CLOSING Based on the recent phase of subsurface investigation, The western pump island area contains significant levels of hydrocarbon in the underlying soil Two vapor extraction wells have been installed in this area and underground piping has been run to each location to affect treatment in this area Soils near the unidentified fiberglass line north of the cashier's booth also contain high levels of hydrocarbon These site assessment activities were conducted during reconstruction of the site During the past two quarters, groundwater monitoring and sampling was suspended due to the reconstruction effort Quarterly monitoring will be continued in the next period when construction will be completed and the wells can be safely accessed The remainder of the proposed subsurface investigation will be continued after site remodeling This work is tentatively scheduled for May 1995 1f you have any questions, please contact Mr Bryan Van Wagner at (310) 923-9876 ext 395. Very truly yours, Peter D'Amico Manager Environmental Affairs cc, CVRWQCB, Elizabeth Thayer