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v � Ms. Margaret Lagorio, SJCEHD February 2,2005 Interim Remedial Action Plan Joe's Truck Plaza, Lathrop, California Page 3 were relatively low, suggesting that the surrounding silty stratum may have laterally restricted the impact reported in well MWO-1X. Costs associated with installing and operating a conventional pump and treat system are likely to be significantly less that for a DPE system. For the purpose of cost comparison, Stratus evaluated projected expenses for a hypothetical period of one year. It is our experience that installation of a DPE system similar to the one utilized in the feasibility test would cost approximately $225,000, including capital costs, installation, and operation (labor, lab costs, and utilities) for one year. This estimated cost does not include installation of larger diameter extraction wells required for efficient DPE operation. A conventional GETS can be installed and operated for one year for approximately $120,000. We believe that existing groundwater monitoring wells can be utilized for groundwater pumping without requiring installation of dedicated extraction wells. Stratus will evaluate the influent concentrations of petroleum hydrocarbons in the extracted groundwater quarterly and determine its cost effectiveness and evaluate switching to another remedial technology. Proposed System Configuration Electric submersible pumps would be installed in wells MW-2, MW-3, and MWO-1X, with the extracted groundwater routed via double-contained, aboveground piping to the treatment system compound (location shown on Figure 2). Extracted groundwater would be treated on-site with three 1,000-pound activated carbon vessels (carbon usage calculations included in Appendix B). The carbon vessels and surge tank would be situated within a confinement structure to prevent accidental discharge of untreated water in the event of vessel leakage. Treated groundwater would be discharged to the sanitary sewer. A proposed process flow diagram for the GETS is included as Figure 7. Stratus has prepared the following scope of work to accomplish the remediation objectives outlined above. The scope of work has been subdivided into tasks 1 through 6. Installation and operation of the proposed GETS will be conducted under the supervision of a State of California Professional Engineer. Task 1 — Design Drawings Stratus will prepare and submit design drawings to procure discharge and building permits from appropriate regulatory agencies. The design drawings will include, but will not be limited to, the following: • Construction details illustrating the system layout and remediation compound, including fencing. • Details for construction of the secondary containment, process piping manifold, and instrumentation. K:Uoe's Truck Plaza\Work PlansUoes]RAP 020205.doc