ARCHIVED REPORTS_XR0012194 - Laserfiche WebLink

Home Browse Search

• Well Installation and Soil Boring Report-Tosco(former Unocal) Service Station 116981, Stockton, CA November 15, 1999 SUMMARY OF PREVIOUS ENVIRONMENTAL ACTIVITIES In May and June 1988,RESNA Industries collected soil samples during replacement of the USTs and from test pits excavated adjacent to the product dispenser islands Petroleum hydrocarbons were detected in soil samples collected from the UST pit,product lines, and test pits Approximately 1,600 cubic yards(yd')of hydrocarbon-impacted soils were excavated and removed from the site Due to the proximity of roads and structures,over-excavation was terminated before all hydrocarbon-impacted soils could be removed A soil vapor survey was performed to assess the extent of residual hydrocarbons in the soil beneath the site Thirteen groundwater monitoring wells, four vapor extraction wells, and one groundwater extraction well were installed at or near the subject site These wells were installed between January 1990 and August 1992 A vapor extraction test(VET)was performed in March 1992 to evaluate the feasibility of vapor extraction as a remedial option for soil beneath the site An aquifer pumping test was performed in August 1992 to evaluate the feasibility of utilizing groundwater extraction to remediate hydrocarbon-impacted groundwater A vapor extraction system has operated at the site since September 1994 To date, approximately 12,000 pounds of gasoline hydrocarbons and 169 pounds of benzene have been extracted and treated The VES is currently being operated on a periodic schedule in pulse mode In February 1996,wells MW-3,MW-10, MW-12,and MW-13 were abandoned at the request of the city of Stockton This work was performed to facilitate reconstruction of the intersection and widening of Pacific Avenue FIELD ACTIVITIES Field work was conducted at the subject site between August 16 and August 18, 1999, when work was suspended Following a delay,fieldwork was resumed and completed on August 23, 1999 Field work was conducted in accordance with GR's Field Methods and Procedures (Appendix A) and Site Safety Plan #140124 05, dated August 16, 1999 Well installation permits 4020163 and#020164 were obtained from the SJCPHS-EHD and a Revocable Permit#99-15 was obtained from the City of Stockton (Appendix B) Underground Service Alert(USA)was notified prior to drilling(reference no 555783),and a private utility locator was contracted to survey the boring locations for underground utilities Drilling Activities On August 16, 17,and 18, 1999,a GR geologist observed Woodward Drilling,Inc (C57#710079)advance four soil borings(MW-14,MW-15,VW-7,and VW-8)at the locations shown on Figure 2 Field activities were observed by Ms Margaret Lagono of the SJCPHS-EHD All borings were drilled with an 8-inch diameter, hollow-stem auger advanced with a truck-mounted drill rig Borings MW-14 and MW-15 were drilled to approximately 41 feet bgs Soil borings VW-7 and VW-8 were advanced beyond the known historic low groundwater level at the site and until there was little or no observable field evidence of hydrocarbon impact(86 feet and 61 feet bgs respectively) Due to obstructions encountered at the proposed location of boring VW-9,field work was suspended until a new location could be determined and cleared On August 23, 1999 fieldwork resumed and boring VW-9 was advanced at the new location No observable 140124 05 2