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3-10 recognized that the area's heavy reliance on groundwater associated with significant population growth and agricultural needs, has resulted in the basin being overdrafted for at least the past 40 years, and water levels have continued to decrease throughout the region. 3.7.2 Local Aquifers The uppermost groundwater beneath the Forward Landfill occurs in the unconfined Victor Formation. Historical groundwater measurements in monitoring wells at the Forward Landfill indicate that groundwater occurs at a depth of approximately 50 to 70 feet below the ground surface with seasonal variations in the groundwater depth of as much as 10 feet; the highest groundwater elevations are observed during the winter/spring and lowest levels in the summer/fall. Groundwater elevations typically range from about -10 feet relative to mean sea level on the southern (Forward Unit) portion of the landfill and about -25 feet relative to MSL on the northern (Austin Road Unit) portion of the landfill. Data acquired by GLA between 2003 and 2009 indicates that, with rare exceptions, the groundwater flows in a north to northeasterly direction at a gradient between 0.001 and 0.003 ft/ft. Although a broad range of hydraulic conductivity values have been assigned to the formational materials (e.g., clay, silt and sand) within the Victor Formation, slug tests performed in four wells at Forward Landfill resulted in hydraulic conductivity values of 2E-02 to 2E-03 cm/sec for the uppermost aquifer beneath the landfill. Based on the maximum hydraulic conductivity of 2E-02 cm/sec, a hydraulic gradient of 0.003, and an estimated effective porosity of 0.2, the maximum groundwater velocity beneath the Forward Landfill is estimated to be approximately 0.85 feet per day. 3.7.3 Local Wells Water supply (non -potable) to the landfill is provided by three on-site wells. The water is used for dust control, compaction, and irrigation. One well, located near the main entrance facility was drilled to a depth of approximately 135 feet and groundwater occurs at a depth of approximately 70 feet. The well was likely installed before the opening of the landfill, having been previously used for agricultural purposes. It is pumped at a rate of approximately 1500 gallons per minute (gpm) at a maximum frequency of approximately 27 times in a 12 -hour day. Another well is located south of the South Branch of Littlejohn's Creek and has a capacity of 500 gpm. The third well is located along the northern boundary of the former Austin Road Landfill. This well was installed in 1972 and has a production of approximately 60 gpm. The fact that groundwater flow near the existing Forward Landfill is not modified by pumping from this well suggests that it is screened in a confined unit below the uppermost groundwater units that are monitored at the site. The sedimentary formations underlying the Victor formation have many productive confined aquifers. In order to develop adequate flow, most of the agricultural irrigation wells in the area are at least 500 feet. The unconfined aquifers are recharged by rainfall and local stream Forward Landfill SWT Engineering Joint Technical Document - April 2014 z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 3_final.doc