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4.Environmental Analysis — TABLE 4.8-1 HYDROLOGIC CHARACTERISTICS OF ADJACENT AND CONTRIBUTING WATERSHEDS TO THE PROJECT SITE Mean Annual Mean Annual Mean Runoff Yield Basin Area Precipitation Runoff (acre-feet per Basin (square-miles) (inches) (acre-feet) square mile) Lone Tree Creek 19.6 11 630 32.2 Hospital Creek 32.2 12 1,300 40.4 Ingram Creek 12.9 10 320 24.8 SOURCE: Nady,P.and L.L.Lamagueta 1983.Estimated Average Annual Stream flow into the Central Valley of California.U.S. Geological Survey Hydrological Investigations Atlas HA-657. received by the watersheds,there are no perennial streams2 near the project site. Project site topography slopes gradually toward the northeast at less than 1 percent with elevations that range — from over 200 feet above msl in the southwest corner to 155 feet above msl along the northeastern border.3 Hospital Creek is an ephemeral stream4 that drains a 32-square-mile basin in the Diablo Range, located south-southwest of the project site.The creek borders the southern boundary of the project site and traverses its southwest corner after crossing over the Delta-Mendota Canal in a box culvert. Hospital Creek continues eastward in a straightened and modified channel both upstream and downstream of the project site. — Modifications to the natural topography to accommodate State Water Project aqueducts and other water conveyance facilities influence existing surface drainage. The Delta-Mendota Canal and the — California Aqueduct are located adjacent to the site and 2,200 feet west of the project site, respectively (Figure 4.8-1). These man-made conveyance facilities have substantially altered the natural drainage because only select streams cross over the aqueduct.These cross-over structures _ and their discharge points control the location and maximum discharge to channels on the down slope side of the aqueducts.Water is present throughout the year in these water conveyance facilities. — Surface Water Quality There is no available data on water quality for site-specific and local tributary streams and drainages. However,based on data gathered from regional water quality studies conducted by the California Regional Water Quality Control Board(RWQCB), it appears that the water quality in 2 Perennial streams are streams that have now at all times of the year. _ 3 The slope represents the change in elevation(rise)across a measured distance(run)and is expressed in units of feet per feet or as a%slope which is the riselrun as a percentage. 4 An ephemeral stream has[lowing water only during and for a short duration after precipitation events in a typical year.Ephemeral stream beds are located above the water table year-round.Groundwater is not a source of water for — the stream.Runoff from rainfall is the primary source of water for stream flow(67 Fed.Reg.2020,2095(January 15,2002). RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.8-2 ESA 1203015 Draft Environmental Impact Report May 2006