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i Work Plan: Subsurface Investigation and Page 2 Remedial Excavation of Hydrocarbon-affected Soil Proposed Cintra Park Phase II Development, Tract 2705, Tracy, California June 17, 1997 CTE Job No. 10-2276 The site lies within a groundwater sub-basin B3 of theSacramento-San Joaquin River Basin (511, [California Department of Water Resources, 1988]). C roundwater resources within this sub-basin have been designated as having beneficial uses for municipal and domestic supply, irrigation, stock watering, and industrial process supply. According to a groundwater map for the area (California Department of Water Resources, 1988), he depth to first groundwater is approxi- mately 10 fbg. Based on an environmental investig tion near the site (Geomatrix, 1996) the direction of groundwater flow is generally to the no west. SITE ASSESSMENT AND REMEDIAL EXCAVATION F HYDR CARBON-AF ECTED SOIL Under this phase of work hydrocarbon-affected soi will be excavated and removed, to the practicable extent, using conventional excavation equipment. Hydrocarbon-affected soil removed during these activities is to be segregated from clean so 11 and trucked from the site to the Forward, Incorporated Class II landfill site in Manteca, Cal Ifornia. Arrangements will be made to temporarily stockpile the excavated soil at the landfill site pending receipt of total lead analyses on a representative sample. Soil samples will be collected during onsite activi ies from the sidewalls and base of the excavations to confirm removal of hydrocarbon-affe ted soils. Soil sampling methodology is discussed in the following section of this workplan. At a minimum one soil sample will be collected for every 100 square feet of excavation si ewall and bottom. Samples will also be collected from apparent "hot spots." Soil samples will be monitored for the potential presence of petroleum hydrocarbons visually and with a gas monitoring detector (Gastech Model 400). Samples selected for combustible gas monitoring will a placed in Zip-Lock or equivalent plastic bags. These samples will be shaken to release any volatiles. A small hole will be poked into the bag, and the sampling port of the Gastech introduced hito the headspace above the soil sample for sampling and analysis. The reading in parts per million of hydrocarbon vapors will be recorded on a field log. SOIL SAMPLING AND LABO TORY ANALYSES Sampling equipment and sleeves will be washed before their initial use onsite and again between sampling events with a TSP detergent solution, and double rinsed with tap water and deionized or distilled water. WARROJECTS11023WENRPOI WPD