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Remed,ation Plan Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 5,0 REMEDIATION APPROACH The SIRIPAR Report provided an evaluation of remedial alternatives for the Unocal site and concluded that connecting "hot" wells at the Unocdl site to the existing Wards treatment system was the most efficient and cost effective interim remedial option for the Unocal site Recommendations for remediation of the area near the RIW were to be determined based on the results of the CPT work around the RIW (see EAI, 200013) The following remediation steps are proposed 6 Connect Unocal wells MW-19S and MW-25S to the vapor extraction header of the Wards remediation system, and Unocal wells MW-19D, MW-23D, MW-25D, and a proposed new air spargmg well (well AS-26) to the air spargmg header of the Wards remediation system (see Figure 2) • Implement biosparging in the area of the RIW utilizing existing wells MW-21D, MW- 22D, MW-24S, and a proposed new well (well AS-27) (see Figure 2) Proposed aii sparging wells AS-26 and AS-27 will be constructed to a depth of 70 feet bgs, and screened between 65 and 70 feet bgs The wells will be 2-inch in diameter and constructed of Schedule 80 PVC The piping connecting the Unocal wells to the Wards site will be installed in a trench to run beneath Robinhood Drive The City of Stockton has verbally indicated that the moratorium on trenching in Robinhood Drive has been lifted Should this not be the case, than it will be necessary to horizontally core beneath Robinhood Drive to install the conveyance piping BS 1232P RAP ADA -8- ENVIRONMENTAL A UDIT,INC