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1 2 �='f investigation necessary to provide data for the preparation of a corrective action plan (CAP), identification of the former underground storage tanks(USTs)installed at the time of the 1967 station remodel,inclusion of soil sampling above and below the current groundwater level until ' the vertical extent of soil contamination has been demonstrated, relocation of the boring proposed in the work plan closer to the center of the known impacted area., redefinition of the ' criteria for the collection of groundwater grab samples to include sampling at changes in hthology, recommendation that vapor extraction and air sparge wells be installed during the ' proposed work, direction to confirm any sample detections of methyl tertiary butyl ether (MTBE) by the EPA Method 8020 with analysis of a suite of fuel oxygenates by a fixed laboratory using EPA method 8260A, and direction that the size of the hollow stem auger to be used for drilling should be specified ARCADIS Geraghty& Miller responded to the SJCPHS comments to the May 26, ' 1998 work plan in a letter dated July 24, 1998 ARCADIS Geraghty& Miller requested that the original portion of the May 26, 1998 work plan which proposed preparation of a Corrective Action Plan (CAP) be withdrawn until such time as SJCPHS and UNOCAL agree that the extent of the release has been adequately characterized by investigation, data ' evaluation, and reporting In the same letter it was also agreed that maps and reports submitted would cite, reference and display the location of the USTs operated prior to the 1 1967 station remodel, and that work would be conducted to identify records on the elevation of shallow groundwater relevant to the Site between the first installation of the Site USTs, or the date of UNOCAL's site lease, and the present ARCADIS Geraghty & Miller disagreed ' with the appropriateness of sampling soils beneath groundwater level and argued that the most appropnate way to characterize and monitor impacts to groundwater was to sample and ' monitor the groundwater medium itself Despite the disagreement, it was agreed that separate soil samples would be taken below the groundwater in the saturated zone as directed by the ' SJCPHS It was also agreed that the proposed soil boring be relocated south and closer to existing well MW-2, and that groundwater samples would be collected at minimum of 10 foot ' intervals from first encountered water to 50 feet, and that below that depth sample would be collected at changes in lithology or a maximum of 10 foot intervals ARCADIS Geraghty &