SITE INFORMATION AND CORRESPONDENCE

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' GORET" Surveys -Final Report • Unresolved peak envelopes(UPEs) are represented as a series of compound peaks clustered together around a central gas chromatograph elution time in the total ion ' chromatogram. Typically, UPEs are indicative of complex fluid mixtures that are present in the subsurface. UPEs observed early in the chromatogram are considered to indicate the presence of more volatile fluids, while UPEs observed later in the ' chromatogram may indicate the presence of less volatile fluids. Multiple UPEs may indicate the presence of multiple complex fluids. • Stacked total ion chromatograms (TICS) are included in Appendix A. The six-digit ' serial number of each module is incorporated into the TIC identification(e.g.: 123456S.D represents module#123456). ' Project Specific Comments: • The minimum(gray) contour level, for each mapped analyte or group of analytes, was set at the maximum blank level observed or the method detection limit, whichever was greater. The maximum contour level was set at the maximum value observed. • In addition to mass results, estimated soil gas concentration values were reported. ' Calculations for concentrations were performed using the mass observed, exposure time, experimentally determined and estimated compound uptake rates, desorption efficiency values, and default soil porosity inputs of 0.459cc/cc total porosity and 0.468cc/cc water filled porosity. A summary of the procedure is included in the appendix. • TPH was detected on the trip blanks and/or the method blanks. Thus, target analyte levels reported for the field-installed modules that exceed trip and method blank levels, and the analyte method detection limit, are more likely to have originated from on-site sources. • The mapped spatial patterns indicated partial plume delineation of PCE, TCE and c 12DCE in the southern portion of the survey area. Isolated"hits"of PCE were detected in the northern section of the survey. • If the objective of the soil gas survey was to delineate the nature and extent of the contamination, then additional soil gas sampling is recommended in those areas where the color contours appear to extend into unsampled areas. Subsequent sampling events can be combined with the data from this event and mapped together to provide greater coverage. ' Page 5 of 5 1 GORE and designs are trademarks of W.L.Gore&Associates