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k" KLEINFELDER <br /> WESTON RANCH <br /> STOCKTON, CALIFORNIA <br /> PROPOSED SCOPE OF WORK <br /> HYDROCARBON STAINS/PS-3 ASSESSMENT <br /> TASK 2.1 HYDROCARBON STAINED AREAS, SOIL AND WATER ASSESSMENT <br /> Six hydrocarbon stained areas (HS-1 through HS-6) were observed and sampled during the <br /> preacquisition site assessment and soil sampling investigation. Total petroleum <br /> hydrocarbons (TPH) were detected from five areas. HS-1 and HS-4 had concentrations <br /> ranging from 270 to 5,600 mg/kg. <br /> TPH concentrations over 1,000 mg/kg are generally considered hazardous waste by the <br /> regulatory agencies, and in San Joaquin County, TPH "cleanup" levels in the soil generally <br /> range from 0 to 100 mg/kg. Because of the TPH concentrations detected, and free water <br /> encountered within 5 feet of the surface at location HS-1, Kleinfelder recommends that the <br /> lateral and vertical extent of soil and possibly water contamination be further assessed at <br /> HS-1 and HS-4. Additionally, an attempt should be made to identify the petroleum <br /> hydrocarbons, and assess the presence of benzene. <br /> Drilling and Sampling <br /> A truck mounted drill rig equipped with 6 or 8-inch hollow stem augers will be used to <br /> advance soil borings to further assess the vertical and lateral extent of contamination. <br /> At HS locations 1 and 4, a boring will be advanced next to the original bore hole location <br /> to assess the vertical extent of contamination. At a minimum, samples will be collected at <br /> 1, 3, 5, and 10 feet. If contamination is indicated at a depth of 10 feet, the borings will be <br /> continued. If free water is encountered, a 2 inch PVC monitoring well will be installed in <br /> the boring. <br /> To assess the lateral extent of contamination, four radial borings (at 90 degree intervals) <br /> will be located approximately 15 feet from the center of the HS boring. Samples will be <br /> collected at 1, 3, 5 & 10 feet if free water is not encountered. If free water is encountered, <br /> the boring will be terminated. <br /> To obtain a preliminary assessment of the water, monitoring wells will be installed in the <br /> center bore hole at each HS location if free water is encountered within the bore hole. <br /> Monitoring wells will not be installed in the radial borings. If water is encountered at only <br /> one HS location, two additional monitoring wells will be installed in the vicinity of that HS <br /> location. If monitoring wells are installed at HS-1 and HS-4, a third monitoring well will be <br /> installed at another HS location or a random location to estimate the ground water flow <br /> direction. Monitoring wells will be screened 10 feet below first encountered water and will <br /> be developed, purged, and sampled. <br /> Chemical Analysis <br /> Soil and water samples from the HS-1 and HS-4 will be submitted under chain-of-custody <br /> to a certified analytical laboratory. Soil samples collected in the earlier investigation were <br /> analyzed for total petroleum hydrocarbons, IR by Method 418.1. This method provides a <br /> cost effective method of assessing the presence of unknown hydrocarbons. One soil sample <br /> collected from the center HS boring will be analyzed for total petroleum hydrocarbons by <br /> 122-88-1160 <br />