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3.0 SELECTED REMEDIATION ENHANCEMENT DESCRIPTION The cleanup equipment and methodologies described in this section were selected to provide the most efficient and cost effective results. Cleanup technologies were based on site-specific knowledge gained during operation of the existing system. 3.1 Cleanup Approach The approach to the final cleanup of hydrocarbon impacts at the Tracy site is conventional and consists of five phases, including 1) limited additional characterization; 2) initial containment and bulk recovery; 3) enhanced product recovery; 4) remediation of dissolved phase impacts, and 5) monitoring and site closure. These phases are listed in general chronological order, although some phases may overlap. The project schedule is provided in more detail in Section 4. Each of the five phases is discussed in greater detail below. 3.1.1 Additional Characterization Phase 1 consists of limited additional site characterization. The site has been adequately characterized from a hydrogeologic standpoint, but to provide additional detail to optimize floating hydrocarbon recovery, product thickness measurements will be performed at approximately four locations in the central plant area. These locations include existing recovery well RW-5A (after it has been shut in for a period of approximately one week), and at the locations of the three additional proposed monitoring/recovery wells shown in Figure 4 If product thickness at any of these locations is less than 0.25 feet after 24 hours, well installation at that location will be reassessed. 3.1.2 Phase 2 - Containment of Impacts and Initial Product Recovery Operation of the Phase 2 recovery system was initiated in 1996 and provides effective groundwater capture and limited hydrocarbon product recovery through the use of a total fluids recovery system (i.e., a well that pumps water and incidental floating petroleum product from below the groundwater surface). The objectives of this system (to provide gradient control and to remove product) have been largely accomplished, with the exceptions noted in Section 2 Floating product and most dissolved phase impacts around recovery well RW-4A have been largely remediated using this system. Phase 2 also includes completed tasks such as removal of impacted soils and the leaking underground pipeline and by using the recovery well system to provide hydraulic capture of the impacted groundwater and product. The operational results of the recovery system are measured quarterly and reported semiannually to the RWQCB. GeoTrans 5