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b 1Weadw�ell&Rolb Mr. Jeffery Wong San Joaquin County Environmental Division 23 December 2003 Page 2 sparging pilot tests. Additionally, in June 2002 a remediation system consisting of ten ozone sparging wells began operation at the site. As this site is scheduled for demolition and redevelopment, all wells must be destroyed and, where appropriate, replaced. The proposed site redevelopment will require that the existing ozone sparging system be removed from the site. Concurrent with the well destruction we are planning to conduct additional sampling to help determine the extent of excavation at the site. After the additional studies are performed recommendations will be made regarding the replacement of the ozone system after site construction is completed. PROPOSED WELL DESTRUCTION A total of 25 wells are proposed for destruction. Two wells are in an area with groundwater impacts and shall be destroyed by drilling out the casings and pressure grouting the holes. Seven monitoring wells, three air sparge wells, three vapor monitoring wells and ten ozone sparging wells are in areas without significant groundwater impacts, and shall be destroyed by pressure grouting the well casings. The area of the site with impacted groundwater is located cross-gradient of the former underground storage tank located in the eastern portion of the site (Figure 1) . There are two monitoring wells, MW-4 and MW-5, located in the area of confirmed or suspected groundwater impacts. The destruction method planned for these wells is to drill out the casings and pressure grout the holes. We request that destruction of these wells be approved by the SJCEHD because of the proposed site redevelopment. After site construction, wells in this area will be replaced as required by the SJCEHD. An additional workplan for this site pertaining to groundwater remediation of this area is also being prepared. Figure 1 shows the former UST area and Table 1 identifies the two wells proposed for destruction by drilling out. The other twenty-three wells at the site are not located in areas of significant groundwater impacts. The planned method of their destruction is to pressure grout them in place. Table 1 identifies the wells proposed for destruction by pressure grouting (MW- 1 through MW-8, SMW-2, VEW- 1 through VEW-3. AS- 1 through AS-3 , and SP-1 through SP- 10). Monitoring wells MW-2, MW-2 and MW-4 through MW-8 did not have any detectable petroleum hydrocarbons or volatile organic compounds (VOCs) in their most recent groundwater sampling, and have had either no or low, sporadic detections of petroleum hydrocarbons or VOCs for several years. Monitoring Well MW-3 has only had sporadic MTBE detections ranging from 2.4 micrograms per liter (ug/L) to 0.67 ug/. All of these wells are on a quarterly sampling program. We request that destruction of these wells be approved by the SJCEHD because data from them has demonstrated that they are not in areas of significant groundwater impacts.