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420 Yosemite, Manteca <br /> Page 2 <br /> Analytical results of soil samples taken from the pipe line south of the excavation and <br /> the stockpiled soil from the excavation also indicated presence of petroleum <br /> contamination. Some of the results are as follows: <br /> P-2: 8,000 ppm TPH-g, 84, 650, 170, 880 ppm BTEX respectively, 690 ppm MTBE, <br /> and 13 ppm TAME. <br /> SPA-2: 1,200 ppm TPH-g, 2.8, 46, 26, 160 ppm BTEX respectively, 5.6 ppm <br /> MTBE, and 660 ppm TAME. <br /> Due to the high groundwater level (between 15 to 20 feet bsg) in the area and the high <br /> concentration of petroleum products in the soil as identified in the analytical results, <br /> PHS/EHD recommends modification to the work plan. Additional soil borings <br /> should be placed in the vicinity of the UST excavation and pipe line. The boring <br /> depths must define the vertical extent of the contaminant plume(s). The depth of the <br /> borings in the vicinity of the UST excavation should be at a minimum to static ground <br /> water level. The borings may have to be drilled below groundwater in order to define <br /> the vertical limit of the contamination. PHS/EHD also recommends the geology of <br /> the site be characterized using technology such as Cone Penetration Technology (CPT) <br /> or continuous core. Soil and groundwater grab samples should be collected for <br /> laboratory analysis using EPA Method 8020 for TPH-g and BTEX at appropriate <br /> detection limits. EPA Method 8260 should be used for analyses of all oxygenates at <br /> appropriate detection limits. The addendum to the work plan should include a plan <br /> for converting strategically selected bore holes (based on field observations) into <br /> monitoring wells. Submit an addendum to the work plan to PHS/EHD by March 20, <br /> 1999. Work must commence by April 10, 1999. <br /> If you have any questions, please feel free to contact Jeffrey Wong at (209) 468-0335. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Jeffrey Wong, REHS Margaret Lagorio, REHS <br /> LOP/Site Mitigation Unit IV Supervisor <br /> c: RWQCB, Central Valley Region-Mark List <br /> c: Advanced GeoEnvironmental, Inc. -Tim Cuellar <br />