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Working To Restore Nature <br /> . approximate hydraulic gradient of 0 001 According to N&B, gasoline hydrocarbons have been <br /> detected in soil and groundwater beneath the site near the tank cavity. <br /> In October 1993, RESNA observed drilling of three off-site bonngs (HP-2, HP-3 and HP-4) and <br /> three on-site bonngs (HP-1, HP-5 and HP-6) The borings were advanced to the water table and <br /> groundwater samples were collected from each boring using a hydropunch sampling device. <br /> RESNA also observed drilling of three additional soil borings on-site near the USTs (B-1, B-2 <br /> and B-3), which were converted to vapor extraction wells VW-I, VW-2 and VW-3 for potential <br /> future use. Analytical results indicated that residual petroleum hydrocarbons in soil and <br /> groundwater beneath the site are apparently limited to a relatively small area in the vicinity of <br /> the former USTs. Soil and groundwater analytical data obtained from previous sampling events <br /> are presented in Tables I and 2, respectively In addition, water quality data for the on-site <br /> domestic well are provided in Table 2. <br /> SUPPLEMENTAL INVESTIGATION <br /> This second phase of the investigation (Phase 2) was conducted in accordance with the <br /> September 15, 1993 workplan prepared by RESNA and the field procedures included as <br /> Attachment 1 <br /> Drilling and_Soil Sampling <br /> On ruly 18 and 19, 1994, a RESRTA f eldeologist observed Western Strata -_x loration <br /> 8 t p <br /> (Westex) of West Sacramento, California advance two off-site borings (MW-4 and iTW-5) and <br /> two on-site borings (MW-6 and MW-7) to depths ganging from 23 to 24 feet below grade at the <br /> project site to accomplish the following. 1) further define the lateral and vertical extent of <br /> petroleum hydrocarbon soil contamination; 2) further determine and define soil stratigraphy; and <br /> 3) install groundwater monitoring wells within the upper most aquifer to assess groundwater <br /> quality. The boring/well Iocations are plotted on Plate 2 <br /> Drilling was conducted utilizing a hollow stem auger drill ng A field geologist continuously <br /> logged all drill cuttings and cored soil samples utilizing the Unified Soil Classification System <br /> (Attachment 2). Cored soil samples were collected at five foot intervals using a 2-inch diameter <br /> split-spoon sampler containing three brass tubes. The cored samples and drill cuttings were <br /> characterized for soil type, moisture content, and evidence of petroleum contamination. <br /> Moreover, a photolomzation detection meter (PID) was used as a screening device for the <br /> detection of petroleum hydrocarbon vapors in drill cuttings and cored samples Soil samples <br /> were collected from each boring at the groundwater interface and below the water table (10 5 <br /> and 15.5 feet below grade, respectively). All samples Were placed immediately on ice and <br /> transported under chain-of-custody to Sparger Technology in Sacramento where they were <br /> analyzed for benzene, toluene, ethylbenzene, xylenes(BT11N), and total petroleum hydrocarbons <br /> as gasoline (TPHg) utilizing EPA methods 8020 and 8015, respectively <br /> 12302018-081694 WP <br />