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t California Regional Water Quality Control Board Central Valley Region Robert Schneider,Chair Winston H.Hickox -, Gray Davis Secretaryfor Fresno Branch Office r,,) Governor Environmental Internet Address: http://www.swrcb.ca.gov/rwgcb5 rw.= Protection 3614 East Ashlan Avenue,Fresno,California 93726 Phone(559)445-5116•FAX(559)445-5910 tom? 19 June 2002 W. Michael Carroll,PE ®� County of San Joaquin' Department of Public Works P.O. Box 1810 Stockton, CA 95201 NORTH CO UNTY RECYCLING CENTER AND SANITAR Y LANDFILL, MOD ULE 4 DEMONSTRATION OF MEETING LINER PERFORMANCE STANDARDS, GALA VERAS COUNTY(Case No. 3161) We have reviewed the Liner Performance Demonstration for Module 4 and Future Modules at the North County Sanitary Landfill(Report), dated 14 May 2002, as prepared by EMCON/OWT, Inc. The County proposes an engineered alternative single composite liner that should be designed to meet or exceed performance standards of Title 27 as required by the Regional Board. The proposed design includes, from bottom to top, a geosynthetic clay layer(GCL) over a prepared subgrade; 60-mil HDPE; gravel leachate collection and removal system(LCRS)ranging from 0.75 feet thick above the HDPE and one- foot thick in areas where leachate collection pipes will be placed in trenches; geosynthetic filter; and a two-foot operations layer of sand. Additional protection will be provided in leachate sump areas. Based on our review,we have determined that there are some areas of concern that must be addressed by the County prior to our acceptance of the liner performance demonstration report as follows: Section 1.2 Proposed Liner System In addition to the containment system presented,the installation of a secondary composite liner system below the leachate removal sump area, equipped with a monitoring and removal system (LCRS), is proposed. Please provide more details on the design and operation of this system. Include information on how the LCRS will be maintained/cleaned out and how it will be tested on an annual basis. Section 1.3 Liner Performance Modeling Results The constituents benzene, 1,2-DCA,methylene chloride,MTBE, vinyl chloride,barium and chloride were selected as modeling parameters. The basis for choosing these constituents was their threat to human health given the high ratio between the constituent's CA Primary MCL and maximum concentration detected in leachate. However, other factors should be considered for choosing constituents, including high human toxicity, high contaminant solubility and transport properties, and whether they are representative of the various chemical groups associated with municipal solid waste California Environmental Protection Agency 00 Recycled Paper The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs,see our Web-site at http://www.swrcb.ca.gov/rwgcb5