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KLEINFELQER EXPECT MORE APPENDIX B BACKGROUND INFORMATION OLWD operates a WWTP in Manteca, California (Plate 1). The former WWTP previously utilized a total of six wastewater percolation/evaporation ponds in series located northeast of the intersection of Walthall Slough and the San Joaquin River. Initially the WWTP accepted domestic wastewater associated with the adjacent mobile home park and the Oakwood Lake Resort (Water Slides) which was conveyed to the treatment plant through a gravity collection system, treated through an activated sludge package treatment system then discharged through the ponds in series. The previous WWTP Ponds 1 through 6 have or will be converted into new ponds for the updated WWTP. The former WWTP Pond No.1 and Pond No.2 have been combined into the current SBR Pond. Former WWTP Pond No. 3 and 4 are/will be converted to a Sludge Pond and Equalization Pond, respectively. Former WWTP Ponds No. 5 and 6 will be combined into a single Emergency Storage Pond. Each of these ponds are to be lined with high density polyethylene or equivalent. The WWTP area/site may be hydraulically connected to the Walthall Slough, the San Joaquin River and Oakwood Lake, based on the proximity of shallow groundwater conditions and flow direction. Please note discussion of Ponds No. 1 through 4 in this workplan refer to proposed holding ponds and the previously numbered WWTP ponds are now referenced per their proposed use (eg SBR, sludge pond, etc). The RWQCB adopted Waste Discharge Requirements (WDRs) Order No. 5-01-113 on May 24, 2001 . A portion of the WDRs required that the OLWD implement a groundwater monitoring program. In order to evaluate groundwater quality and potential impacts, a portion of the WDR directed the OLWD to install and sample groundwater monitoring wells at the site. On July 15, 2001 Holdredge and Kull prepared a "Proposed Groundwater Sampling Work Plan," for implementation of the groundwater monitoring portion of WDR Order No. 5-01-113. The workplan was subsequently approved in a document titled, "Conditional Approval of Groundwater Sampling Workplan," prepared by the California Regional Water Quality Control Board, Central Valley Region on August 2, 2001. Holdredge and Kull installed nine wells MW-1 through MW-9 at the site. Four monitoring wells MW-1 through MW-4 were installed in the vicinity of the six wastewater ponds. Three of the wells MW-5 through MW-7 were installed in the northeast portion of the site near a shallow pond (Proposed Holding Pond No. 1 Area) and two wells MW-8 and MW-9 were installed in the southeast portion of the site (Proposed application Area C). Monitoring wells MW-5 through MW-9 were apparently installed to evaluate background groundwater conditions prior to implementation/discharge wastewater to future ponds and application areas. Holdredge and Kull conducted quarterly groundwater sampling between November 2001 and May 2004. Monitoring wells MW-8 and MW-9 according to county records (well destruction permit) referenced by the RWQCB were destroyed in April of 2005 and the last groundwater sampling data 48093.E01/ST07R052/CJC/Iv Page B-1 ©2007 Kleinfelder, Inc January 26, 2007