SITE INFORMATION AND CORRESPONDENCE

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ARCO Meeting Minutes •W, August 8, 1994 Page 4 f z ARCO 2076, Lodi (Mary Meays) total xylenes was detected in MW-3 Mary said that she had received the first quarter status report and brought during the fourth quarter of 1993. that stated thathe t reported concentration was 0.7 ppb which is below MCLs and contamination could have easily t occurred in the laboratory (dirty glassware,cross contamination, etc.). In additioonly sampling event in over a year which resulted in the detection of hydrocarbons n is was the groundwater. Laboratory results on groundwater samples collected during the first and second quarter of 1994 confirm that hydrocarbons are not present in the groundwater. Mary asked when ARCO would be scheduling remediation of the impacted soil. ARCO stated that a select number of abatement units have been allocated for San Joaquin County, and that ARCO intends to focus remediation efforts on those sites which have the highest amount of the site to begin after six months. ARCO explained to Mary that his schedu et was rempendent on contamination or pose the greatest risk to groundwater and therefore ion of the availability and performance of remediation systems operating in the county. ARCO 548, Stockton, (Mary Meays) sections, remedial alternatives, VET results, etc.). EMCON submitted an addendum to the Mary said that she had received the quarterly status reporVPAR and that the PAR was deficient in areas outlined in her correspondence o ARCO and requested additional inform ation (cross P at the meeting presenting this additional information. EMCON explained to Ma AR conversations with her, an abbreviated PAR would be excepted since only a limited amount of data had been collected since submitting the Preliminary Investigation and Evaluation Report. Mary said that this was now not the case and complete PAR was required. EMCON told Mary that the addendum that was submitted that date should satisfy all PAR requirements. Mary said that based on the first quarter status report, it appears that dissolved hydrocarbon t concentrations have increased and extend off-site. ARCO stated that the results of the first quarter sampling event may not accurate Mary that ARCO begin using a new groundwater sampling cont the ntractater or he begin R1�Oof explained to data collected from some sites are likely incorrect. EMCON informed Mary that the results of second quarter sampling event show that the concentrations are back to levels that 994 and , f consistent with previous quarters and that hydrocarbons do not extend off-site. Mary said that 1 she will review that data once she has received the report. Mary asked ARCO if the source has been eliminated and implied that there is an ongoing leak from the tanks. ARCO replied by saying that the tanks and lines have been tested and are within the allotted parameters. Mary questioned the general validity of tank testing stating that the tests are not accurate and is sure that leakage is occurring. Diane Hinson redirected the discussion stating that the dialogue was based on conjecture. Mary asked ARCO what type of remediation implemented. EMCON stated that remediation by soil vapor extraction appears to be thea most effective remedial alternative. Mary asked how groundwater was going to be remediated. EMCON said that the majority of dissolved hydrocarbons are located in the vicinity of the USTs 3 and within the effective radius of influence of the vapor extraction system. ARCO said that remediation of groundwater was not going to be ignored and will monitor the effects the vapor extraction system has on the groundwater. Active groundwater remediationf sparging, etc.) will not be implemented at this time but the need will be evaluated during treat, air operation of the vapor extraction system and be discussed in future quarterly status reports.