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pollution that affect the quality of industrial storm water discharges and to describe and ensure the implementation of practices to reduce pollutants in industrial storm water discharges. The objectives of the monitoring program are to (1) demonstrate compliance with the permit, (2) demonstrate compliance in the implementation of the SWPPP, and (3) measure the effectiveness of the Best Management Practices (BMPs) in removing pollutants in industrial storm water discharge. In general, the purpose of this permit is to prohibit non -storm water discharges (including 'illicit connections") and discharges containing hazardous substances in storm water in excess of reportable quantities established in 40 CFR 117.3 and 40 CFR 302.4. Artificial Water -Carrying Structures The Banta-Carbona Irrigation District Canal trends north -south, and bounds the western margin of the project. The Delta -Mendota Canal lies approximately 1/2 mile west of the project. The California Aqueduct lies approximately 1.5 mile west of the project. The canal and aqueduct trend northwest - southeast. Ground Water The project site is near the western edge of the large regional ground water basin that underlies California's Central Valley. The inactive Black Butte Fault is located about 2 miles west of the site, and forms the western edge of the ground water basin. The fault juxtaposes Jurassic and Cretaceous marine sedimentary rocks against the younger and unconsolidated alluvial deposits in the ground water basin. The upper part of the ground water basin, to a depth of about 100 feet, consists of the Pleistocene to recent alluvial fan deposits previously described in Section 4.4. The project site is underlain by the Tulare Formation, the principle source of ground water on the east side of the San Joaquin Valley in the area of the project. The Tulare Formation serves as the major reservoir for subsurface pumping of water for the west sides of San Joaquin and Stanislaus Counties. The Tulare Formation is composed of continental, semi -consolidated, poorly sorted, discontinuous deposits of clay, silt, and gravel. Tulare Formation crops out as a thin band in the lower foothills of the Diablo Range to the west of the project and dips steeply northeastward into the valley. The formation dips on the order of 15 to 20 degrees at its outcrop area, but flattens and thickens in the vicinity of Tracy. In the Tracy -Patterson area, the Tulare Formation ranges in thickness to 1,100 feet. A regionally extensive clay layer, known as the Corcoran Clay Member of the Tulare Formation, occurs near the top of the formation, and confines the underlying high-quality fresh water deposits. This Corcoran Clay is readily recognizable, and is usually logged as a "blue clay" in water well driller's reports. In the Tracy area, the blue clay is interbedded with yellow clay and silt. The clay is the most extensive hydrologic confining layer in the San Joaquin Valley, and underlies about 3,500 square miles of bottom land and western slopes. In the Tracy area, the Corcoran Clay can vary from near zero to about 150 feet thick. In the vicinity of the project, the Corcoran Clay occurs at a depth of approximately 300 feet. The Corcoran Clay separates the ground water system into shallow and deep portions, which have different water levels, flow directions, and water quality. The direction of shallow ground water flow is toward the northeast, indicating a source of recharge near the western edge of the basin. Recharge of the shallow system is from deep percolation of irrigation water, infiltration of rainfall, seepage of stream flow out of Corral Hollow Creek and other creeks, and subsurface inflow from the consolidated rocks adjacent to the basin. The amounts of recharge from each of these sources is not known precisely for the vicinity of the project site. In 1964, deep ground water flowed north or northwest, and appeared to be water of Sierra Nevada mountain origin (DWR, 1967). The project site is in the Tracy -Patterson Ground Water Storage Unit of Davis and others, 1959. This unit includes the belt of coalesced alluvial fans in the northwestern part of the valley, between the San Joaquin River and the uplands of the Coast Ranges. The estimated ground water storage capacity of the Tracy - Patterson storage unit is 4,040,000 acre feet (Davis, et al, 1959). In the Tracy -Patterson area, yields to wells from the Tulare Formation range from about 40 gallons per minute to 3,300 gallons per minute, and ER -93-1 -65- (9-27-93) Li L I r C G n u u u C C' C'