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yn. ..� 15 August 2001 AGE-NC Project No. 95-0184 Page 2 of 3 PURPOSE On 27 July 1998 the PHS-EHD approved by letter the recommendations provided in the AGE-prepared Quarterly Report-April 1998. The recommendations were: • Additional soil borings and monitoring wells should be installed to define the horizontal extent of hydrocarbon-impacted soil and ground water. A work plan for the installation of additional monitoring wells has been approved by the PHS-EHD. • A soil vapor extraction/in-situ air sparging (SVE/IARS) pilot test should be conducted to evaluate remediation options for this site.Findings of the vapor extraction/air sparging test can be used to determine the spacings of potential additional vapor and sparging wells. However,because: 1)the extent of contamination is undefined,2)most of the monitoring and vapor extraction wells are"drowned"and 3)there appears to be two distinct contamination plumes,AGE hereby proposes a revision to the recommendations listed in the July 1998 quarterly report. SCOPE OF WORK Prior to the installation of additional vapor extraction and monitoring wells and SVE/IARS pilot testing, AGE proposes to advance four paired CPT soil borings to collect soil textural data and ground water samples (Figure 2); one pair at each of the two UST locations, another pair east- southeast of UST location #2 on Miner Street, and the remaining pair approximately 160 feet northeast of UST location#1,to help delineate vertical as well as the lateral extent of impacted soil and ground water and define the water-bearing zones at the site. One of the paired borings at each location will be a cone-penetrometer test to help determine lithology and flow units; the other, adjacent boring will be advanced to collect water and/or soil samples in key water-bearing zones as interpreted from the initial CPT boring.The borings will be advanced to a nominal depth of 100 feet below surface grade(bsg); if petroleum hydrocarbon odor is detected in the water sample collected at total depth, additional water samples will be collected from deeper intervals until a depth is reached where no hydrocarbon odor is detected. Based on the results of the CPT survey, shallow-screened and deep-screened monitoring and vapor extraction wells will be installed,and soil vapor extraction/in-situ air sparging pilot tests will follow. The wells will be.designed to monitor potential zones of migration of impacted soil and ground water as identified by the CPT results. Procedures for the installation and sampling of the monitoring and extraction wells were described in the AGE-prepared WorkPlan Addendum,dated 15 December 1995 and Quarterly Report-August 1997;the precise boring locations will be based upon access agreements with neighboring property owners and the city of Stockton, and the locations of underground utilities. Final designs for the additional monitoring and extraction wells will be submitted to the PHS-EHD for approval prior to installation. Advanced GwEnvironmentd,Inc