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1 Additional Soil and Groundwater Investigation Report Canepa's Car Wash(Park Street) ' May 8,2002 Page 7 HP13 indicate that the shallow groundwater immediately north of the site has been impacted by ' moderate and low concentrations of gasoline constituents, respectively The location of HP 13 appears to be near the northwest extent of the shallow groundwater plume The results of the groundwater samples collected from HP 19, HP20, and HP21, well below the current water table, indicate that the lateral and ' vertical extent of groundwater contamination have not been fully investigated north of the site The highest concentrations of gasoline constituents were detected in the shallow groundwater sample 1 collected from HP14 near the former location of the USTs with benzene at 15,000 µg/L East of HP14, concentrations of benzene are 3 to 4 orders of magnitude less, down to a concentration below the laboratory reporting limit at HP18 near the sidewalk MTBE was detected at low concentrations in the ' groundwater samples collected from HP7, HP 15, HP 16, and HP 18 MTBE was not detected at or above the laboratory reported detection limit in any of the other groundwater samples collected during the investigation The MTBE iso-concentration contours constructed with the shallow groundwater data ' from the current investigation (Figure 5, Appendix A) indicate a low concentration MTBE plume The plume is apparently from an off-site source located southwest of the site and not from the former USTs at the site The low concentrations of benzene in the locations of HP 15, HP 16, and HP 17 may also be from an off-site source located southwest of the site based on the distribution of the benzene contamination in that area In summary, Condor believes that the lateral extent of shallow groundwater at the site has been adequately investigated except possibly due north of monitor well MW-5 and hydropunch sample HP 12 The vertical extent of groundwater contamination, however, has not been fully investigated in the lie locations of CPTI and CPT2 and laterally in all directions down-gradient from those locations 6 0 RECOMMENDATIONS Condor recommends additional groundwater investigation at the site, particularly to further evaluate the vertical distribution of the contaminant plume Specifically, Condor recommends the preparation of a work plan to describe the methods and procedures to adequately investigate the vertical extent of gasoline contamination at and near the site The investigation would include additional CPT borings and discrete depth sampling and probably follow-up monitor well installation i ' 7.0 LIMITATIONS Condor developed the interpretations and conclusions presented herein in accordance with generally accepted principles and practice Conclusions presented in this report are professional opinions based on ' limited information obtained at the time of our site visits Condor has endeavored to determine as much as practical about the site using conventional practices given our scope of services Condor makes no representation as to the subsurface conditions at locations or times other than those sampled by our ' employees and reported in this document If any changes are made or errors found in the information utilized in this report, the interpretations and conclusions contained herein shall not be considered valid unless the changes are reviewed by Condor and either appropriately modified or re-approved in writing ' Condor's involvement in the work performed at this site has been limited to observing the installation of CPT borings, a soil boring, and hydropunch samples, collecting of samples, shipping of samples, ' compiling data provided by analytical laboratories, and analysis of field data Condor is not responsible for the accuracy and completeness of information collected and developed by others at this site and at adjacent sites 1 ' �,, CONDOR