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• Draft Supplemental Environmental Impact Report Page IV.G-7 • Forward Inc. Landfill 2018 Expansion Project • Surface water discharge from the onsite stormwater/sedimentation ponds to the creek is • monitored quarterly. However, surface water discharges from the onsite ponds to the creek • only occur during unusually high rainfall season events. Since 2008 time, all surface water has • been retained onsite, even during the relatively high rainfall year of 2016-2017. There were no • reported detectable VOCs in the surface water samples collected in the 2017 annual report • (GLA, 2017c). A comparison of the upgradient and downgradient surface water samples showed similar inorganic constituent concentrations,suggesting the landfill units are not • significantly impacting surface water quality. • NPDES Storm water Monitoring Program • • The Forward Landfill has a current NPDES monitoring program and SWPPP in place. These • programs, overseen by the RWQCB, include stonnwater inspection, sampling, observation, and • reporting. Previously, treated groundwater was discharged to receiving waters at Little John Creek but that has been replaced by use of the treated groundwater to: 1)use for onsite dust • suppression and other operations uses, or 2) use for artificial recharge reinjection into the local • aquifer. As the landfill expands, the facility is required to update its NPDES and SWPPP. • Groundwater • Regional Groundwater Conditions Underlying San Joaquin County is a portion of the vast subsurface groundwater aquifer system • of the Central Valley of California. Groundwater occurs in unconfined and confined conditions. • Previous Forward Landfill EIRs have presented the regional hydrogeological conditions, which • have not changed. The upper regional aquifer is typically an unconfined aquifer within the Victor Formation geologic unit. A minor perched water table at an elevation of about 20 feet • ams] was encountered while drilling one of the site wells; perched water tables in the area are of • a limited extent. The Victor Formation consists of over 100 feet of interbedded clay, silt, and fine • to coarse sand and gravel. Sedimentary formations underlying the Victor Formation include • additional, productive aquifers. Groundwater within 1 mile of the site is tapped by irrigation and domestic wells, and most such wells in the vicinity are generally drilled to a depth of • several hundred feet. Many of the sedimentary formations underlying the Victor formation • have productive confined aquifers. In order to develop adequate flow, most of the agricultural • irrigation wells in the area are at least 500 feet deep. • Groundwater recharge to the unconfined aquifer,both regionally and locally, is from local • rainfall and stream infiltration, while the deeper, confined aquifers are recharged by rivers, • reservoirs, and surface runoff along the western base of the Sierra Nevada. The project area is not in a General Plan-designated substantial groundwater recharge area, although some • infiltration and percolation to the groundwater system is expected along Littlejohn Creek.' • • • Hydrogeological investigations at the Forward Landfill show that recharge along the course of the • south fork of Little John Creek,which crosses that property,has a significant influence on water table • depth, gradient, and flow direction in the localized creek area. • • • •