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2.0 DRAINAGE DESIGN CRITERIAHYDROLOGICAL CRITERIA <br /> The ten (10)and hundred (100) year 24-hour storm events were used as the CJK Specialty <br /> Aggregates stormwater control measure (CM) design criteria. Runoff estimates used the criteria <br /> set forth by Urban Hydrology/or Small Watersheds, TR-SS by the United States Department of <br /> Agriculture (USDA), Natural Resources Conservation Service (MRCS), Conservation <br /> Engineering Division,dated June 1986. Copies ofthe runoff worksheets can be found in <br /> Appendix A. <br /> Design rainfall estimates are obtained from National Oceanic and Atmospheric Administration <br /> (NOAA) Precipitation Frequency Data Server website. The values for Leadville are obtained <br /> from NOAA Atlas 14, Volume 8. Version 2. The 10-year 24-hour storm is 0.64 inches and 2.48 <br /> inches for the 100 year 24-hour event. <br /> There is no direct runoff from the 10 year whereas and 100-year 24-hour storm event is 0.64 <br /> inches. See Appendix A-1 - 10 year-24-hour storm) and 100 year-24-hour storm. (See Table 1) <br /> The NRCS Soil Survey (Appendix A-2) beneath the slag piles is Leadville Sandy Loam, 3 to <br /> 35 percent slopes. The soils are well drained and consist of stony and cobbly, medium-textured <br /> alluvium; and stony and medium cobbly, medium textured till. <br /> The conservative runoff curve number(RCN) for the porous slag Industrial zone is 70. <br /> Hydraulic Criteria <br /> There are few defined drainage channels or rivulets within the study area. Sheet wash or <br /> channels less than two feet deep within the study area drains directly to California Gulch. See <br /> Figure 2 <br /> 3.0 DRAINAGE BASINS AND SUB BASINSDESCRIPTION <br /> The CJK Specialty Aggregates property is not located in a Flood Hazard Area according to the <br /> FEMA FoodInsurance Rate Map: Community Panel No. 080282-0004 A, dated March 1, 1998. <br /> 4.0 FACILITY DRAINAGE <br /> General Concept <br /> The drainage plan is allowing for the planned facility improvements without altering the <br /> natural drainage patterns or water quality of the area. Runoff from non-impacted areas are kept <br /> separatedand directed away from impacted areas. <br /> Runoff for the 10 year and 100-year 24-hour storms (See Table 1) <br /> from disturbed areas will be managed for the 10 year-24-hour storm will be using a <br /> combination of rock barriers, swales, and check dams, <br /> Open Channels <br /> Rock barriers swales and check dams are used to convey surface flows from the property. The <br /> 4.30.2021 <br />