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r) <br /> F, <br /> Workplan: Groundwater Investigation Page 2 , <br /> Proposed Cintra Park Phase II Development, Tract 2705 <br /> Tracv, California <br /> December 8. 1997 CTE Job No. 20-0445 <br /> i <br /> • The lateral and vertical extent of hydrocarbon-affected soil onsite was generally assessed and <br /> removed. Hydrocarbon-affected soil remaining onsite apparently is limited in extent (four <br /> excavation sidewall and bottom soil samples contained TPH-G concentrations of 2.0 mg/kg <br /> For less). Field analytical results were interpret d to indicate that hydrocarbon-affected soil <br /> (at each of the four detected locations) is gener lly confined to areas of approximately five <br /> - feet horizontally and less than two feet vertically. <br /> a< . <br /> • Groundwater, encountered at an approximatedepth of eight fbg, has been slightly impacted <br /> by the petroleum hydrocarbons. However, no Free product was detected at any time in the <br /> a , excavations. <br /> Information regarding historic groundwater levels in the site area was requested from the San <br /> Joaquin County Flood Control and Water Conservation District. However, according to the <br /> interviewed personnel, the district does not have any wells nearby and they do not have information <br /> on historic groundwater levels in the Tracy area. <br /> I <br /> OBJECTIVE AND PROPOSED WORK <br /> F The purpose of proposed work is to assess the exte t of possible groundwater contamination at <br /> P rP P P P <br /> 7 this site. Three soil borings will be advanced by a subcontractor using 10-inch hollow stem augers <br /> on a truck-mounted drill rigs. Drilling activities will be observed by a Geologist from Construction <br /> Testing and Engineering, Inc. ("CTE"). As shown on the attached Figure the proposed borings will <br /> be drilled in the area of the remedial excavations and down and across the expected groundwater <br /> gradient. Before drilling soil boring/groundwater well permits will be obtained by the drilling <br /> subcontractor from the San Joaquin County, Public Health Services, Environmental Health Division <br /> (PHS/EHD). <br /> Soil samples will be collected, at five-foot intervals, lithologic.changes, and immediately(<one foot) <br /> r- above the groundwater table. Soil samples will be logged in the field using the Unified Soil <br /> Classification System. Soil samples will be monito ed for the potential presence of petroleum <br /> hydrocarbons as outlined below. Selected samples will be retained for potential laboratory analysis <br /> by capping them with a Teflon sheet liner and a plastic cap. Collected samples will be identified by <br /> boring number and depth. <br /> Monitoring of soil samples for the potential presence o petroleum hydrocarbons will occur visually <br /> and with a gas-monitoring detector (Gastech Model 4 0) using the following procedure. Selected <br /> � soil samples will be placed in Zip-Lock or similar plastic bags for combustible gas testing. The soil <br /> F.+ samples will be shaken to-release volatile constituents, a small hole will be poked into the bag, and <br /> F, 11WORD\CIPROJE=,2004451Workplan-GW well.doc <br /> F.' <br />