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STATE OF CALIFORNIA GEORGE DEUKMEJIAN, Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— CENTRAL VALLEY REGION 3443 ROUTIER ROAD, SUITE AF SACRAMENT A ,. O, C 95827 3098 NOV 5 1090 1 November 1990 ENVIRONMENTAL HEA-! Ti,' PERM IT/SERVi,",) Mr. Tom Horton Solid Waste Manager San Joaquin County Department of Public Works P.O. Box 1810 Stockton, CA 952 NORTH COUNTY LANDFILL, SAN JOAQUIN COUNTY, CASE NO. 3161 Landfill Specification B.18. in Waste Discharge Requirements (WDR) Order No. 89-199 (adopted in October 1989) specified that waste management units at the North County Landfill be underlain by a clay liner with a minimum thickness of 12 inches. On 5 July 1990, San Joaquin County proposed to replace the clay liner with a 60 mil High Density Polyethylene (HDPE) liner. After meeting with the County, Jeff Tucker signed a letter on 8 August 1990 approving the use of the HDPE liner contingent upon receiving a QA/QC plan and subsequent Regional Board approval of the plan. Mr. Tucker's letter should be regarded as Regional Board staff's approval of the technical concept of replacing the clay liner with HDPE. A properly constructed HDPE liner will be more effective in preventing leachate migration through the bottom of the landfill . HDPE is also more effective in stopping migration of organic solvents that are typically found in landfill leachate. These solvents penetrate clays rather quickly. In order for the County to construct the HDPE liner it will be necessary for the Regional Board to amend Order No. 89-199 to allow the use of HDPE in place of the required clay liner. This is a minor change to the waste discharge requirements and could be proposed for adoption at the Regional Board's January 1991 meeting. The County must demonstrate that the HDPE liner is an engineered alternative under Section 2510 of Title 23 California Code of Regulations, Division 3 Chapter 15 (Chapter 15) . We request that the County submit a Technical Report to our office by 28 November 1990 which demonstrates that the HDPE liner is a feasible engineered alternative under Section 2510 of Chapter 15. Submittal of the technical report by 28 November 1990 is necessary so that we can schedule a WDR amendment for the January 1991 Regional Board meeting. Also, at least 60 days prior to construction, the County must submit a Quality Assurance/Quality Control (QA/QC) Plan that demonstrates that the liner will be constructed to meet performance goals. An Operations Plan is also required prior to landfilling operations demonstrating how the HDPE liner will be protected during landfilling operations.