CORRESPONDENCE_2007 (1/07 - 6/07)

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F CENTRAL VALLE EGIONAL WATER QUALITY #NTROL BOARD INSPECTION REPORT DATE: 27 March 2007 FACILITY: Corral Hollow Sanitary Landfill DISCHARGER: San Joaquin County Public Works LOCATION & COUNTY: Tracy, San Joaquin County CONTACT(S): Michael Carroll INSPECTION DATE: March 26, 2007 INSPECTED BY: Todd Del Frate ACCOMPANIED BY: SUMMARY: Met Michael Carroll of San Joaquin County (SJC) Public Works at the Corral Hollow Sanitary Landfill (CHSL) site. The CHSL is a closed, unlined, Class III sanitary landfill maintained by the County. The purpose of the site visit was to inspect the facility and acquire a thorough understanding of the spatial relationship between the landfill boundaries, monitoring and gas wells, and the proposed boring locations requested to further delineate the LFG issues observed at the site. The CHSL is a relatively small landfill covering approximately 40 acres. The landfill has been in corrective action since 2001 and a LFG system has been operating since that time. Groundwater has been impacted in the vicinity of well MW-5, located in the northeast corner of the landfill. LFG has been observed in all gas wells surrounding the site. The County will be conducting an investigation to delineate LFG in soil and groundwater and staff reviewed several of the proposed locations during this site inspection. The boring locations northwest of the CHSL are located across Corral Hollow Road, approximately 200 to 300 feet northwest of MW-5. The borings northeast of MW-5 are proposed across the Interstate 580. The distance in this direction appeared to be quite far and staff discussed this with the Discharger. Staff has concerns that borings across the Interstate are far enough out to get"ND", which will not provide any further characterization information northeast of MW-5 (Figure 1). Staff requested the County discuss intermediate locations with consultant and to look at drilling in the shoulder or median. Borings have also been recommended south of the site in the vicinity of GW-6. Staff has also requested an additional well be installed near this location. Figure 2 indicates a fair amount of off-site area that could be explored to satisfy an investigation south of the site. The CHSL has a well established vegetative cover as shown in Figure 3. The vegetation appeared mature, thick, and full and no erosion rills or channels were observed. LFG does not appear to be venting through cover since bare spots were not observed. SJC pointed out several low spots where standing water was observed during the 2006/2007 wet season. Staff inspected primary and secondary storm water retention ponds shown in Figures 4 and 5. Standing water was not observed in either of the ponds. Staff inspected the LFG system (i.e. flare, condensate tank, blowers, and control panels). The system seemed to be well maintained and running efficiently. Figure 6 is an overview shot of the LFG system. Overall, the CHSL Approved: