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Mr. Greg Vaughn Project No. OC42-001.20 <br /> April 11, 1995 <br /> Page 3 <br /> HYDROPUNCH GROUNDWATER SAMPLING <br /> EMCON proposes to collect groundwater samples from the C- and D-zone sands <br /> identified in CPT profiles at selected locations to further define the dissolved petroleum <br /> hydrocarbon impacts and assist in placement of groundwater monitoring wells. <br /> Approximately ten HydroPunch samples are proposed in the C- and D-zones at locations <br /> adjacent to CPT locations. Sample intervals will be determined following evaluation of the <br /> CPT profiles. <br /> EMCON proposes to use the HydroPunch II® sampler to collect groundwater samples <br /> consistent with procedures described in the Phase H Assessment Report (EMCON, <br /> September 1994). The sampler will be driven to the target depth using the CPT rig. C- and <br /> D-zone water samples will be collected from the same boring by advancing the sampler to <br /> the target depth, collecting the sample, and removing the sampler for decontamination. <br /> After the sampler and rods are decontaminated, the sampler will be lowered into the <br /> boring and advanced to the deeper sample interval. After sampling activities are <br /> completed, the borings will be sealed with bentonite grout tremied from the base of the <br /> boring to ground surface. Decontamination procedures will consist of steamcleaning the <br /> sampler and rods after each sample is collected. Decontamination water will be drummed <br /> for disposal. <br /> EXPLORATORY BORINGS AND MONITORING WELL INSTALLATION <br /> The RWQCB requires groundwater monitoring well installation to confirm HydroPunch <br /> groundwater sample analytical results collected during the phase II assessment locations <br /> and for future assessment locations. Specific phase II monitoring well locations were cited <br /> as "must install' in the RWQCB comments, and additional well locations for purposes of <br /> HydroPunch sample confirmation were indicated. EMCON re-evaluated the proposed well <br /> locations with respect to existing well locations and the extent of dissolved hydrocarbon <br /> impacts. In order to avoid installing monitoring wells with limited long term utility for <br /> monitoring and remediation purposes, EMCON revised well locations, reducing the <br /> overall number of monitoring wells required while providing monitoring wells at locations <br /> with long term monitoring and remediation applications. General well locations are shown <br /> on Drawing 1 and summarized on Table 1. Monitoring wells along the eastern margins of <br /> the C- and D-zone plumes will be installed either within areas 6 and 7 or within areas 9 <br /> and 10, based upon plume margin definition from HydroPunch samples. Evaluation of <br /> proposed Phase II monitoring well locations with respect to overall utility and need is <br /> presented on Table 2. Installation procedures are described in the following paragraphs. <br /> Exploratory borings will be drilled using air-rotary casing hammer drilling equipment to <br /> minimize potential for cross-contaminating deeper water-bearing zones and to reduce the <br /> SAC,�N:\PJMC4Z\K.4200I2.OES-94VIb:3 <br />