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o PAH impacts in soil were identified in five of the six AOIs (AOIs 1, 2, 3, 4 and 6) at maximum depths of 3 feet bgs. TPH impacts in soil were observed in AOIs 3, 4 and 6. TPH impacts were observed to depths of between 10 and 15 feet bgs in AOIs 3 and 4, and only to approximately 3 feet bgs in AOI 6. VOC impacts in soil were only observed in AOI 4 and are co-located with the PAH and TPH impacts. o VOC impacts in soil gas were observed in two AOIs. AOI 4 is directly adjacent to the former gasoline UST and contains elevated soil gas VOC concentrations typical of a gasoline related release. AOI 5 is associated with PCE concentrations detected in Al-SGI, the source of which is unknown. However, results from step out soil gas points located within 10 feet of Al-SG1 show that results decrease rapidly in a relatively short distance away from Al-SG 1. o Groundwater impacts were only observed in AOI 4 during the first round of sampling conducted at the Site. TPH impacts were observed in groundwater at a maximum concentration of 350 ug/L (TPH-d). A total of six VOCs were identified in RI sample results at relatively low concentrations. During the second round of sampling conducted for the SSI, the only detected constituent was MTBE (at 1.2 ug/L). All other COPCs had no detectable concentrations. Groundwater impacts in AOI 4 have been identified but it is anticipated that no remedial efforts will be required to manage impacted groundwater. If future groundwater remedial efforts are required, it is anticipated that they will be limited to monitored natural attenuation. 6.3 RECOMMENDATIONS Based on the conclusions generated through the analysis of data from the RI/SSI and previous investigations, the following recommendations have been developed: • An HRA scoping meeting should be conducted to determine the process by which the HRA will be developed. This meeting should be conducted with project personnel from DTSC including a HERD representative and the project manager; and representatives from PG&E and their consultants [Parsons and Iris Environmental (health risk assessment contractor)]. After this meeting, a technical memorandum will be submitted to DTSC for review, comment and approval. • An HRA should be completed using the data generated as part of the RI/SSI and previous investigation, and in accordance with agreed upon approach developed during the HRA scoping meeting outlined above; and • Thereafter, the HRA should be incorporated into a streamlined HRA/FS/RAW document, to be submitted to DTSC for review and approval. The HRA/FS/RAW will address remedial management of each of the AOIs. PARSONS 48 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010