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Ms.Margaret Lagorio,SJCEHD October 21,2003 Joe's Truck Plaza Project No.2033-15600-01 Work Plan for Additional Site Assessment Page 6 sandy zone is in hydraulic communication with the water in the upper sandy zone, to evaluate the groundwater flow regime in the lower sandy zone, and to characterize if, or to what extent, the lower sandy zone has been impacted by dissolved gasoline constituents. Data evaluated for the SCM suggest that much of the residual gasoline compounds beneath the site are found in the vicinity of the northern UST's. To evaluate the feasibility of extracting residual mass for remediation, Stratus proposes to conduct both GWE and DPE feasibility tests. Because the SCM suggests that, as constructed, well MWO-1X might be providing a vertical conduit allowing communication between the upper and lower sandy zones, Stratus proposes to properly destroy this well by drilling it out to total depth, backfilling it with cement to the top of the hard clay (approximately 18 feet bgs), and constructing extraction well EX-1 in the remaining borehole. This proposed extraction well would be screened wholly within the upper sandy zone. Existing monitoring wells MW-1 and MW-2, and proposed monitoring wells MW-7, MW-8, and MW-18 will be used to observe the effects of GWE and DPE in the upper sandy zone. Deeper-screened well DW-2 will be utilized to observe if the GWE and DPE tests affect groundwater in the lower sandy zone. As an interim measure, Stratus proposes to install fifteen ozone sparge wells (IW-1 through IW-15). These wells willl be screened near the base of the upper sandy zone. The purpose of the ozone is to supplement the dissolved oxygen levels in the groundwater to enhance the biogenic breakdown and natural attenuation of the MTBE. Ozone sparging is a cost effective means of addressing the MTBE concentrations identified northeast of the site. This technology appears to provide immediate reduction in MTBE concentrations. Stratus has had success using ozone sparging at other sites in San Joaquin County. Wells MW-3 and MW-8 through MW-12 will be utilized to monitor the effectiveness of the ozone sparging. The proposed scope of work presented above has been subdivided into tasks 1 through 5. All geologic work will be conducted under the supervision of a State of California Registered Geologist or Registered Engineer, and will be conducted in accordance with standards established by the Tri-Regional Board Guidelines for Hydrocarbon Site Assessment and Remediation (RWQCB 1991) and SJCEHD guidelines. Additional information regarding Stratus' field practices and procedures is presented in Appendix A. Task 1: Pre-Field Activities Following approval of this work plan by SJCEHD, the following activities will be implemented: • Secure an access agreement and encroachment permit for installation of off-site wells. P:\Joe's Truck Plaza\Work Plans\Joes workplan 102103.doc