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24 May 2021 <br />Project No. 14-3002 <br />Page 6 of 23 <br /> <br />northern and southern portions of the Great Valley Province have been designated the <br />Sacramento and San Joaquin Valleys, respectively. <br /> <br />The subject property and surrounding area lie within the San Joaquin Valley Groundwater <br />Basin, Eastern San Joaquin Subbasin (5-22.01). This subbasin is bound on the south, <br />southwest, and west by the Modesto, Delta-Mendota, and Tracy Subbasins, respectively, <br />and on the northwest and north by the Solano, South American, and Cosumnes <br />Subbasins. The Solano and South American are subbasins of the Sacramento Valley <br />Groundwater Basin. The Eastern San Joaquin Subbasin is drained by the San Joaquin <br />River and several of its major tributaries, namely, the Stanislaus, and Calaveras, and <br />Mokelumne Rivers. The San Joaquin River flows northward into the Sacramento and San <br />Joaquin Delta and discharges into the San Francisco Bay. <br /> <br />The closest surface water feature to the Site is the San Joaquin River located <br />approximately 1.1 miles to the southwest. <br /> <br /> <br />2.6. STORMWATER AND WEATHER <br /> <br />Stormwater from the Facility area was channeled to a collection pond located adjacent to <br />the southern edge of the power plant. The collection pond is located between the Facility <br />and the undeveloped/unsurfaced portion of the Site to the south. Stormwater infiltrates <br />into the ground from the collection pond and the unsurfaced areas of the Site. Presently, <br />stormwater that falls on the Facility runs off into the collection pond and pools in some of <br />the concrete structures remaining in the Facility area. <br /> <br />Annual precipitation data for the area was obtained from the California Irrigation <br />Management Information System (CIMIS) Manteca Station #70. Manteca Station #70 has <br />been collecting precipitation data since January 2014. The annual rainfall average for the <br />area between 2014 and 2020 was 11.52 inches. <br /> <br /> <br />2.7. HISTORIC OPERATIONS AND PCB SOURCES <br /> <br />A 48-Megawatt gas fired power plant operated in the northern portion of the property <br />between 1990 and 2013 (Facility). The Facility operated as a simple cycle power plant <br />producing electricity and ancillary services for dispatch and sale. The generation facility <br />operation started around 1990 and used a natural gas-fed combustion turbine to provide <br />electrical power to the region during peak usage periods. When the Facility was <br />operational, several locations on the Site were used for operations. Water for the Facility <br />was supplied by the City of Lathrop and wastewater was piped into a vault, tested prior <br />to discharge, and then pumped into the municipal sewer system (drinking water for the <br />Site was delivered in bottles). Solid waste generated by the Facility was removed by <br />contracted carriers. An abandoned wastewater injection well was located at the southeast <br />corner of the operations area. The injection well was officially closed on 14 April 2003.