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F 0 <br /> I <br /> Workplan: Groundwater Investigation Page 2 <br /> Proposed Cintra Park Phase II Development, Tract 2 05 <br /> Tracy, California <br /> December 8, 1997 CTE Job No. 20-0445 <br /> • The lateral and vertical extent of hydrocarbon-aected 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 co tained TPH-G concentrations of 2.0 mg/kg <br /> or less). Field analytical results were interpreted to indicate that hydrocarbon-affected soil <br /> (at each of the four detected locations) is generally confined to areas of approximately five <br /> feet horizontally and less than two feet vertically. <br /> • Groundwater, encountered at an approximate d pth of eight Ibg,has been slightly impacted <br /> by the petroleum hydrocarbons. However, no ftee product was detected at any time in the <br /> excavations. <br /> Information regarding historic groundwater levels in the site area was requested from the San <br /> Joaquin County Flood Control and Water Conserva ion 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 /> OBJECTIVE AND PROPOSED WORK <br /> The purpose of the proposed work is to assess the exte t.of possible groundwater contamination at <br /> 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 Heath Services, Environmental Health Division <br /> (PHS/EHD). <br /> Soil samples will be collected, at five-foot intervals,lith logic changes, and immediately(<one foot) <br /> above the groundwater table. Soil samples will be I ogged in the field using the Unified Soil <br /> Classification System. Soil samples will be monitored 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 of petroleum hydrocarbons will occur visually <br /> and with a gas-monitoring detector(Gastech Model 4C0)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 /> samples will be shaken to release volatile constituents, a small hole will be poked into the bag, and <br /> \1WORD\CIPROJECTS12004451Workplan-GW well.doc <br />