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—COUNTY— Greatness COUNTY— Greatness grows here. July 24, 2018 Mr. Todd Del Frate, PG Engineering Geologist Central Valley California Regional Water Quality Control Board 11020 Sun Center Drive, #200 Rancho Cordova, California 95670 Department of Public Works Kris Balaji, Director of Public Works Fritz Buchman, Deputy DirectoM)eve/opment Michael Selling, Deputy DirectorlEngineen.ng Jim Stone, Deputy DirectorlOperations Kristi Rhea, Manager of Strategic Initiatives SUBJECT: FIRST SEMIANNUAL 2018 GROUNDWATER AND SURFACE WATER MONITORING REPORT, NORTH COUNTY RECYCLING CENTER AND SANITARY LANDFILL Dear Mr. Del Frate: Enclosed is the First Semi-annual 2018 Groundwater and Surface Water Monitoring Report for the North County Recycling Center and Sanitary Landfill (NCRCSL), submitted in accordance with Waste Discharge Requirements R5-2010-0016. Below is a summary of the findings: Due to low groundwater levels, samples for chemical analysis could not be collected from wells G -1A, G -2A, G -3D, G-4, G -5A, and G-6 during the first or second quarter events. However, groundwater monitoring wells G-7 and G-8 are down gradient from the landfill and provide a monitoring network for the determination of a release from the site. One additional down gradient groundwater monitoring well (G-9) was installed in September 2017 and was sampled during the first semiannual 2018 monitoring event. Three additional monitoring wells, G-56, G-10, and G-11, were installed in February and March 2018 and were sampled during the first semiannual 2018 monitoring event. Of these three new wells, G -5B and G-11 are down gradient of the landfill. G-10 is the new up gradient well for the landfill. The concentrations of field and monitoring parameters for down gradient wells G-56, G-7, and G-11 and up gradient well G-10 were below established concentration limits (CLs). The upper CL for pH was exceeded at monitoring well G-8. The CLs for turbidity and calcium were exceeded at monitoring well G-9. Although samples could not be collected from wells G -2A, G -3D, G-4, G -5A, or G-6, water level measurements could be collected for determining groundwater flow direction. During the first quarter, the flow direction was northwesterly and southwesterly from the east. During the second quarter, the flow direction was southwesterly. VOCs were not reported in down gradient monitoring wells G-513, G-7, G-8, or G-11 or in up gradient monitoring well G-10 during this semiannual period. One trace level VOC, carbon disulfide, was reported at well G-9. Double retest confirmation samples were collected from well G-9 and the VOC detection was not confirmed. The lysimeters did not yield enough water for sampling, indicating no detectable leaks from the liner in those areas. Unsaturated zone monitoring will continue in accordance with the WDRs. Results of leachate monitoring are consistent with past leachate monitoring events. The first semiannual 1810 East Hazelton Avenue I Stockton, California 95205 1 T 209 468 3000 I F 209 468 2999