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Additional Phase II Environmental Site Assessment Report Buena Vista Storm Drain,Stockton,CA August 15,2005 Page 4 6.0 DISCUSSION The only constituent detected in the groundwater samples collected during the previous Phase II ESA was MTBE from boring GP-5, so the groundwater samples collected from the borings advanced on July 26, 2005, were analyzed only for potential gasoline constituents (TPH-G, BTEX, and gasoline oxygenates/additives). None of the constituents were detected at or above the laboratory reported detection limits in any of the groundwater samples collected from borings GP-13 through GP-16. Our investigation was limited to approximately 50 feet to the east and west and 45 feet to the northeast and northwest of boring GP-5. Groundwater samples were not collected on the property located at 1930 West Fremont Street, believed to potentially be the source of the MTBE detected in the groundwater sample collected from boring GP-5. Groundwater with detectable concentrations of MTBE that is extracted during construction dewatering will most likely have to be treated for removal of the MTBE before it can be discharged to the sanitary sewer. 7.0 RECOMMENDATIONS Condor recommends considering the need to sample and possibly treat groundwater extracted during construction dewatering. Though MTBE was detected only in the groundwater sample collected from boring GP-5 and not in the additional step-out borings, groundwater contaminated with MTBE may be drawn towards dewatering pumps located in the vicinity of nearby borings where MTBE was not detected. 8.0 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. Soil samples were not collected for analysis during this investigation and the extent of soil contamination is unknown. Groundwater sampling was limited to depths of 20 feet below the existing ground surface. Contamination in groundwater may be present at depths greater than the depths tested during this investigation. 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. ow W CONDOR