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& California.Regional Water Quality Co of Board <br /> Central Valley Region <br /> Robert Schneider,Chair <br /> Linda S.Adams Arnold <br /> Secretaryfor Sacramento Main Office Schwarzenegger <br /> Environmental 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Governor <br /> Protection Phone(916)464-3291 •FAX(916)464-4645 <br /> http://www.waterboards.ca.gov/centralvalley <br /> 17 November 2006 NOV 2 0 <br /> E VIROINMEN1 HEALTr <br /> W. Michael Carroll PERMIT/SERV!cES <br /> San Joaquin County Dept. of Public Works <br /> Solid Waste Division <br /> P.O. Box 1810 <br /> Stockton, CA 95201 <br /> REVIEW OF PHASE 2 INVESTIGATION OF EXTENT OF CLOSURE CAP, CORRAL <br /> HOLLOW SANITARY LANDFILL, SAN JOAQUIN COUNTY <br /> The Regional Water Quality Control Board (Regional Water Board) staff has reviewed the <br /> Phase 2 Investigation of Extent of Closure Cap and Health and Safety Plan (Report) for the <br /> Corral Hollow Sanitary Landfill. The Report was received electronically on 31 October 2006. <br /> Recently additional waste was discovered outside the current footprint of this closed landfill. <br /> This Report proposes additional subsurface work to define the extent of the current closure <br /> cap for the purpose of extending the closure cap east over the recently discovered refuse. <br /> Previous investigations conducted in the vicinity of the drainage ditch revealed refuse in <br /> excavations 1 through 3, and 5 as described in a report dated 3 March 2006. The March <br /> report included detailed field drawings of five excavations trenched in September 2005. <br /> According to the procedure section of the report, the Discharger excavated on the east and <br /> west sides of the eastern landfill road to define the horizontal extent of refuse. The depth of <br /> the excavations were 6 feet if refuse was not encountered and 12 feet if refuse was <br /> encountered. The deeper excavations were an attempt to determine the vertical extent of the <br /> waste. <br /> According to the field drawings, refuse was encountered in excavations 1 through 3, and 5. <br /> Refuse appears to have been defined both horizontally and vertically east and west of the <br /> eastern landfill road in excavations 2, 3, and 5. However, refuse encountered in excavation 1 <br /> was not defined vertically east or west of the eastern landfill road. Excavation 1 was explored <br /> to a depth of 12 feet west of the eastern landfill road and only explored to a depth of 4 feet <br /> east of the landfill road. Refuse was not encountered in excavation 4. <br /> The Report proposes to define the eastern edge of the closure cap on the landfill for purpose <br /> of tying this cap into the cap proposed for the newly discovered waste. The investigation will <br /> explore the closure cap on approximately 100-foot centers between previous excavations 1 <br /> and 3. The Discharger proposes to inspect each pothole for the prescriptive clay barrier. <br /> Following inspection, each pothole will be partially backfilled to the clay barrier where a <br /> minimum 2-inch thick granular bentonite seal abutting the clay barrier will be placed. The <br /> pothole will then be backfilled to surface grade and compacted with excavated soil. Once the <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />