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STATE OF CALIFORNIA PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION <br /> 3443 ROUTIER ROAD, SUITE A <br /> SACRAMENTO, CA 95827 <br /> -3098 V 6 - <br /> PHONE: (916) 361-5600 <br /> FAX: (916) 361-5686 JUN 2 4 1991 <br /> �VVIR ONMENTAL HEALTH <br /> 19 June 1991 pLRMIT/F>ERV10EG <br /> Mr. Gabe Karem <br /> Department of Public Works <br /> County of San Joaquin <br /> P.O. Box 1810 <br /> Stockton, CA 95201 <br /> VADOSE ZONE MONITORING PLAN, NORTH COUNTY SANITARY LANDFILL, SAN JOAQUIN <br /> COUNTY (CASE# 3161) <br /> We have reviewed the Vadose Zone Monitoring Plan (Plan) -dated January 1991 for <br /> North County Sanitary Landfill . The Plan states that a set of lysimeters and <br /> electrical resistance (soil moisture) blocks will be placed upgradient of <br /> Module 1&2 and beneath the leachate sump for Module 1&2 (the lowest point in <br /> the fill module) . <br /> The purpose of the monitoring plan is to provide early detection of leaks in <br /> the liner. Using only two vadose zone monitoring stations in a 25 acre module <br /> is not adequate. While it is true that moisture leaking from the landfill <br /> into the leachate collection and recovery system (LCRS) would eventually flow <br /> into the leachate sump, a leak from the LCRS into the vadose zone may take a <br /> significant amount of time to reach the vadose zone monitoring station beneath <br /> the leachate sump, if at all . <br /> At least three more vadose zone monitoring stations are needed beneath Module <br /> 1&2. The number and locations of these stations should be based on the area <br /> of influence of the lysimeters and lithology in the upper layer of the vadose <br /> zone. <br /> If you have any questions, please contact me at (916) 361-5737. <br /> ROBERT A. EVANS <br /> Area Engineer <br /> RAE <br /> cc: Mr. Bill Orr, California Integrated Waste Management Board, Sacramento <br /> Mr. Ed Padilla, San Joaquin County Public Health Services, Stockton <br /> Mr. J.C. Isham, EMCON Associates, Sacramento <br />