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Langston's Alarket 1561 S.SeventDi V1reet, Lathrop, California October 5, 1995 Interint Secopidai V Source Remnval c- Illonttoring Well Replacement Page: 3 I ' All the above OVM readings represent the maximum re tdkng registered by the 580B instrument during the screening of each sample Although OVM readings do not precisely,/ correspond to chemical analysis the readings approximate the amount of gasoline present in the soil in part s-per-milhon (ppm), of total petroleum hydrocarbon constituents As the above analyses indicate, a significant amount of gasoline remains in the Vadose zone soil at the site Only borings SB-1, SB-7, and SB 8 appeared to be free of significant amount of total petroleum hydrocarbons Due to the shallow depth of the water table ' (17 5 feet), it is therefore not surer,sing to find that groundwater quality has been+ impacted by the release 01, nearly 1200, gallons of gasoline from the failed underground fuel tank Borings SB-5 and SB-6�were dulled directly beneuh the centei and the failed end of the former tank respectively Tne highest OVM readings were found throughout the soil column in these two 1^ratio s, (onfirirli�.g that the "oui�.e of the ga,;oline in the soil of iginated from the former underground fuel tank 3.0 Scope of Work On July 27 1995 WRF Inc in conjunction with SEMCO9 Inc , under a San Joaquin I County approved workplan, dated October 11, 1994 began iinterim remedial activities at this site with the removal of surface structures and trench slotting to further define the limits of contamination The water table was measured at appro-umately 161/r feet below ground level The four existing groundwater monitoring wells were then abandoned, I under permit, to avoid the possibility of cross-contamin tion Excavation of uncontaminated soil continued down to approximately 15112 feet below ground level Excavation of contaminated soil continued down to an average depth of 25 feet, with the aide of a de-watering well Contaminated soil was trucked directly to Forwai d Landfill, Stockton, California and stockpiled for characterization and disposal Pumped water was treated and discharged to the City of Lathrop sewer system and City of Manteca treatment plant After the excavation had progressed to its maximum limit due to roads and utilities, compacted backfilling began Replacement of the groundwater monitoring wells was Iconducted 'between September 21 and 23, 1995 31 Demolition of Structureii After an asbestos survey and obtaininb encorachment and demolition permits from the City of Lathrop, SEMCO began demolition of all structures at 15615 Seventh Street, Lathrop, Califotnia, on July 27, 1995 (.Appendix I) Demolition was completed and exploration trenches were dug to delineate the estimated limits of contanunation and to determine the placement of tht) equipment, r