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t <br /> Field Screening <br /> Field screening will primarily determine the need for additional <br /> Geoprobe sampling locations. In addition to visual and olfactory <br /> observations, soil and groundwater samples will be screened with a PID <br /> for headspace analysis. The analysis will be used for field screening <br /> purposes only since it is not intended to be a substitute for laboratory <br /> analysis. A portion of soil from each sample will be placed and sealed <br /> in a labeled Ziploc bag (or equivalent); groundwater samples will be <br /> placed in a clear glass jar and covered and sealed with foil. The <br /> samples will be warmed in the sun or other uncontaminated heat <br /> source to allow any volatile hydrocarbons present to vaporize and <br /> collect in the headspace. After adjusting the PID calibration to read <br /> zero for ambient air, the bag or foil will be punctured by the PID probe, <br /> and a sample will be drawn to detect any organic vapors present. <br /> Headspace analysis results will be recorded directly on the lithologic <br /> logs. <br /> Geoprobe Sample Analysis <br /> Based on the information about the known content of USTs 517-1 and <br /> 517-2, soil and groundwater samples from this site will be screened and <br /> all samples will be analyzed for TPH-diesel, TPH-gasoline, and BTEX <br /> compounds. All soil and groundwater samples from Sump 816D, <br /> Sump 617, and Sump 816D will be screened and all samples will also be <br /> analyzed for TPH as diesel (TPH-diesel), TPH-gasoline, BTEX <br /> compounds, VOCs, semivolatile organic compounds (SVOCs), and <br /> PCBs. For both soil and groundwater samples, TPH-diesel and TPH- <br /> gasoline will be analyzed by USEPA Method 8015 (Modified), and BTEX <br /> will be analyzed by USEPA Methods 8020. In addition to the above- <br /> listed chemical compounds, five metals (cadmium, chromium, lead, <br /> zinc, and nickel) will also be analyzed. <br /> Phase II - Monitoring Well Installation <br /> To provide long-term monitoring and determine whether fuel- <br /> affected groundwater is migrating off-site, monitoring wells will be <br /> installed at each UST site using the hollow-stem auger drilling <br /> method. Since monitoring well locations will be based on the results <br /> of Phase I Geoprobe sampling, proposed monitoring well locations are <br /> not shown on site location figures. <br /> A minimum of three monitoring wells are proposed for each UST site. <br /> The monitoring wells will be installed in a triangular orientation with <br /> 4-5 <br />