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Soil Sampling During Station Demolition, Tosco(Former Unocal) SS#6981, Stockton, CA August 29, 2000 detected in soil samples collected from the UST pit, product lines, and test pits Approximately 1,600 cubic yards (yd3) 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, six vapor extraction wells (VW-1 through VW-6), 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 As of the first quarter 2000, since startup of the system in 1994, 14,747 pounds of Total Petroleum Hydrocarbons as gasoline (TPHg) and 183 pounds benzene have been removed 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 To replace abandoned wells MW-3, MW-10, MW-12, and MW-3, GR, installed three groundwater monitoring wells (MW-14, MW-15,and MW-16),one groundwater spargmg well(VW-7), and advanced one soil boring (VW-9) in August 1999 The new monitoring wells and sparge well were subsequently added to the sites' quarterly monitoring program VELD WORK Sampling work associated with the site demolition activities was conducted by GR Sampling was performed in accordance with the GR Field Methods and Procedures (Appendix A) All soil samples collected during this investigation were delivered under chain-of-custody to Sequoia Analytical Laboratory in Sacramento (FLAP #1624) Analytical methods and results are summarized in Table 1 Copies of the laboratory analytical reports and chain-of-custody records are attached (Appendix B) Mr Michael Kith of the SJCPHS-EHD was present at the site during UST removal and associated soil and stockpile sampling activities Ms Margaret Lagono of the SJCPHS-EHD was also present during UST removal activities and dunng over-excavation and associated soil sampling activities Demolition and soil excavation were performed by Fuller Excavation and Demolition,Inc (Fuller)of Rancho Cordova,CA Compliance Sampling On April 26,2000,Fuller removed two 12,000-gallon, double-walled, steel with a fiberglass-wrapped shell, gasoline USTs Upon removal,the USTs were visually inspected for evidence of failure by a GR geologist and a representative from the SJCPHS-EHD All the removed tanks were in good condition with no observed cracks or holes The USTs were transported by Fuller to Ecology Control Industnes' (BCI) facility in Richmond, California, for destruction Uniform Hazardous Waste Manifests and tank destruction certificates are attached(Appendix C) Lunits of excavation are shown on Figure 3 140124 07 2