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Contingency Work Plan For Excavation of Soil a. Chevron Station N9-3232 <br /> January 21 1999 <br /> of 52.6 and 0 .901 ppm, respectively. Samples from boring MW-2 did not contain TPHg, BTEX, or <br /> MtBE in the 10 and 20.5 foot samples. However, TPHg and benzene were detected in the 30 .5, 40.5, <br /> and 50. 5 samples at increasing concentrations from 2.94 to 593 ppm and 0 . 1 84to 6.44 ppm, respectively. <br /> On November 4, 1998, groundwater was recorded at depths between 31 .93 and 36.07 feet bsg. The flow <br /> direction was to the southwest at a gradient of 0.05 . Samples from each of the wells contained <br /> concentrations of TPHg and BTEX. Well MW-2 located in the down gradient direction of the dispenser <br /> islands had the highest concentrations of TPHg ( 120,000 ppb) and benzene (23 ,000 ppb). Fuel <br /> oxygenate compounds were not detected in any of the groundwater samples. <br /> SCOPE OF WORK <br /> The purpose of the proposed scope of work is to attempt to delineate any impacted soil after UST and . <br /> piping removal (February 25, 1999) and prior to new construction activities (March 21, 1999). The <br /> scope of work proposed includes : <br /> 1 . Collecting the required compliance samples from beneath the former USTs, steel <br /> product piping, and fiberglass piping. <br /> 2. Excavation of soil to evaluate hydrocarbon impact if detected . <br /> 3 . Disposition of stockpiled soil. <br /> 4. Soil Borings . <br /> Task 1 . Compliance Sampling & Possible Excavation of Soil to Evaluate Hydrocarbon <br /> Impact if Detected. <br /> Upon removal of the USTs, fiberglass and former steel piping, compliance soil samples will be <br /> collected from native soil and submitted for analyses as directed by San Joaquin County Public <br /> Health Service Agency (SJCPHS). Should the analytical data indicate that the soil is <br /> substantially impacted by petroleum hydrocarbons, we propose to evaluate the extent of <br /> hydrocarbon impact by excavation. A backhoe or excavator will be utilized to explore outside <br /> and Beneath the areas of hydrocarbon impact to evaluate the lateral and possible vertical extent <br /> of impact. Tire depth and number of samples collected will depend on the initial analytical <br /> results from the compliance soil samples collected beneath the former USTs and piping. The <br /> soil samples collected during exploration will be analyzed for the constituents detected in the <br /> compliance samples. Soil excavated to evaluate hydrocarbon impact will be stockpiled onsite <br /> separately from other soil (backfill material) and covered with plastic sheeting pending <br /> analytical data. Should analytical results indicate that the compliance samples do not contain <br /> hydrocarbon impact, excavation will not be implemented. <br /> Task 2. Disposition of Stockpiled Soil <br /> If pea gravel was used as the backfill around the existing USTs, it will be stockpiled separately <br /> onsite and inspected for visible signs of liquid hydrocarbons. If liquid hydrocarbons are not <br /> present, Chevron proposes to re-use the pea gravel as backfill material without further <br /> CH93232.WP2 - 2 346463 .02 <br />