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No Further Action Request Lo 640 N.San Joaquin Street,Stockton,CA October 9,2002 Page 9 13. Results of mass balance calculations of hydrocarbons remaining in the soil are presented in Section 4.0. 4. 14. Assumptions, parameters, calculation results, and the model used in the risk evaluations are discussed in Section 3.0 or presented in the results of the risk evaluations located in Appendix D. La IS. Results of the risk evaluation described in Section 3.0 indicate that there is no Baseline Carcinogenic Risk due to contamination of soil and groundwater at the site. The evaluation results also indicate that the Baseline Toxic Effects limit of 1.0 is not exceeded by either the Hazard Quotient or the Hazard Index. Although concentrations of motor oil were detected in the groundwater sample collected from boring B-3 near TK I, it is Condor's opinion that the laboratory analytical results for the groundwater sample collected from boring B-3 represents cross-contamination of the sample during advancement Lo of the boring. In addition, the groundwater elevation is significantly (>30 feet bgs) below the zone of impacted soil (<16 feet bgs). The site is paved with asphalt, so infiltration of surface water through contaminated soil in the vadose zone and into the groundwater at the site should be negligible. V 16. No WET or TCLP analyses were performed on any of the samples collected at the site. 7.0 REQUEST FOR NO FURTHER ACTION LW On behalf of David and Marianne Warwick, Condor respectfully requests no further action at the site in accordance with "low risk groundwater" criteria included in Appendix B of the Tri-Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites Alo Further Action Requests. Risk evaluation results indicate that there is no Baseline Carcinogenic [tisk due to contamination of soil and groundwater at the site and that the Baseline Toxic Effects limit of 1.0 is not exceeded by either the Hazard Quotient or the Hazard Index. Based on the results of the soil and groundwater investigation and the sensitive receptor survey, Condor believes that the potential for a significant impact to the site groundwater and identified sensitive receptors is insignificant. It appears that only the lower mobility fractions of diesel and motor oil were found in the site subsurface during the soil and groundwater investigation. The area of the site above the contaminated soil and groundwater is paved so the risk of infiltration of surface water through the contaminated soil to groundwater, and volatilization of contaminants in the soi I and groundwater to outdoor air, is minimal. &, 8.0 LIMITATIONS The scope of work for the sensitive receptor survey was limited to a review of documents provided by DWR for the area within a 2,000-foot radius of the site and a reconnaissance of the area within a 500-Foot �+ radius of the site. The reconnaissance consisted of observation of the area from public streets. The scope of work did not include observation of the interior of structures that could potentially contain water wells, but consisted of visually identifying wells that were readily observable and not enclosed or hidden from �.. view. Condor assumes no responsibility for any inaccuracies or incompleteness presented in documents provided by the DWR. 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 W CONDOR 6W