SITE INFORMATION AND CORRESPONDENCE FILE 1

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i ARCO Meeting Minutes August 8, 1994 Page 4 ARCO 2076, Lodi (Mary Meays) Mary said that she had received the first quarter status report and brought to our attention that total xylenes was detected in MW-3 during the fourth quarter of 1993. EMCON stated that the reported concentration was 0. 7 ppb which is below MCLS and contamination could have easily occurred in the laboratory (dirty glassware, cross contamination, etc.) . In addition , this was the only sampling event in over a year which resulted in the detection of hydrocarbons in 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 contamination or pose the greatest risk to groundwater and therefore anticipate remediation of the site to begin after six months. ARCO explained to Mary that this schedule was dependent on the availability and performance of remediation systems operating in the county. ARCO 5481 Stockton, (Mary Meays) Mary said that she had received the quarterly status report/PAR and that the PAR was deficient in areas outlined in her correspondence to ARCO and requested additional information (cross sections, remedial alternatives, VET results, etc.). EMCON submitted an addendum to the PAR at the meeting presenting this additional information. EMCON explained to Mary that based on 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 concentrations have increased and extend off-site. ARCO stated that the results of the first quarter sampling event may not accurately present the groundwater quality. ARCO explained to Mary that ARCO begin using a new groundwater sampling contractor the beginning of 1994 and 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 Ievels that are consistent with previous quarters and that hydrocarbons do not extend off- she will review that data once she has received the report. site. Mary said that Mary asked ARCO if the source has been eliminated and implied that there is an ongoing from the tanks. ARCO replied by saying that 9 ng leak 9 the t the I auks an ' allotted d lines shave parameters, Mary questioned the general v been tested and are within are not occur validity of t ate and is sure Y tank testing stating that I 9 tin the leakage nj occurring. Diane Hinson redirected the discussion tests stating that the dialogue was based on conjecture. Mary asked ARCO what type of remediation efforts were planned and when they would be implemented. EMCON stated that remediation by soil vapor extraction appears to be the most effective remedial afternative. Mary asked how groundwater was EMCON said that the majority going to be rem 1 of di edi ss ated and � °�� hydrocarbons are within the effective radius of influence of the vapor extraction system. ARCO aid thain the vicinity of the t STs remediation of groundwater was not going to be ignored and will monitor the effects the vapor extraction system has on the groundwater. Active groundwater remediation (pump and treat, air sparging, etc.) will not be implemented at this time but the need will be evaluated during operation of the vapor extraction system and be discussed in future quarterly status reports.