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<br />2001 -3- 003-2142.6 <br />The BMP sump is designed to contain two times the 10-year, 24-hour storm water runoff <br />from the upstream watershed, as shown on Drawing 1. The resulting sump volume is 1.1 <br />acre-feet. The sump will be constructed as a subgrade depression into the existing fill. <br />The outflow structures for the Arequa Gulch and Crusher sedimentation ponds, Bateman <br />Creek detention pond, and BMP sump aze sized to route the 100-year, 24-hour storm event <br />The Bateman Creek detention pond size was developed from the results of the HEC-1 <br />analysis for the 100-year, 24-hour storm event. The pond design is presented in Drawing 2 <br />of this report. The pond is sized to have a capacity of 1.1 acre-feet, with a spillway to safely <br />route the 100-yeaz, 24-hour storm event. The pond will be located at the outfall point of the <br />84-inch CSP that routes run-off from the Phase IV Valley Leach Facility diversion ditch, <br />beneath the re-aligned Highway 67. The pond will be constructed as a partial subgrade <br />excavation with a small earthen embankment and an outflow structure with riprap armoring <br />for erosion control. <br />3.0 REFERENCES <br />Hydrologic Engineering Center, 1990. HEC-1 Flood Hydrograph Package User's Manual, <br />U.S. Army Corps. of Engineers, Davis, California. <br />ooc Golder Associates <br />