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t Langston's Market I 15615 Seventh Street, Lathrop, Cakfonva October 24, 1994 Remedial Excavation Work Plan Page: 3 I As the above analyses mdu ate, a significant amount of gasoline remains m the Vadose zone sod at the site Only borings SB-3, SB-7, and SB-8 appeared to be fi-ee of significant amount of tail petroleum hydrocarbons Due to the shallow depth of the water table (17 5 feet), it is therefore not surprising to find that groundwater quality has been impacted by the release of nearly 1,200 gallons of gasoline from the faded I End fuel tank Bormgs SB-5 and SB- 6 were drilled directly beneath the center and the faded end of the former tank respectively The highest OVM readings were found throughout the soil column in these two locations, confirming that the source of the gasoline in the soil originated from the former underground fuel tank. 3.0 Site Rork Plan E lIwgtson Undo the direction of WBC's registered professional, SEMCO proposes to characterize the cow zone by locating the previous borings, and excavating slots to determine the vatical and lateral extent of contamination The eansting monitormg wells will be located and determined if one or more must be properly closed before vaavation begins Due to the existing budding location directly over the contaminated zone, sanely soil condmons, and high probabi'ht'y of sort caving, the buildmg must be removed from the site prior to excavation activities. Approximately 3,000 tons of soil wdl be excavated from the contaminated zone (Figure 2) Approxamate]y 1400 tons may be fim of mon and potentially used for backfill material Care will be exercised durmg excavation to separate the soil in two or more groups, "apparent clean" and "appareirt contaminated" All soil excavated and stockpiled will be sampled and analyzed by a state certified laboratory to determine appropriate disposmon. The analytical results wilt be reviewed and submitted to an approved disposal fiiimility The excavation will be constructed wrth a 1 1 slope in compliance with Cal OSHA regulations In the event sloping is not possible due to work space constraints, a shoring plan wM be developed. During the excavation process the cxmtaminated groeiadwater and free product will be primped from the excavation to temporary storage tanks as necessary to minimize saturation of the excavated soil. In the event saturation of the soil occurs, a reme pre=9ion will be exercised to prevent cross coiita nination of surface soil The final phase of the excavation will be completed in one work shift if possible due to the potential of a large volume o£water entering the mon.