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<br />2.1 Storm Type <br />• The Storm Type was selected as SCS 't'ype iL The SEDCAD+ model (hydrogtaph convolution interval) time <br />increment was selected as 0.1 hour. <br />2.2 Rainfall Depth <br />The rainfall depth fora 10-year, 24-hour, storm event was determined [o be 1.90 inches [National Oceanic and <br />Atmospheric Administration (NOAA) Atlas 2, Precipitation - Frequenry Atlas of the Western United States, <br />Volume III -Colorado; and previous reports]. <br />3. SEDCAD+ INPUT PARAMETERS COMMON TO ONE OR <br />MORE AREAS <br />3.1 Soil Parameters <br />SEDCAD+ soil input parameters include [he particle size distribution of "erodible material" [that portion <br />passing the 4 millimeter (mm) size sieve], whether the soil at the site has been disturbed, the erodibility (a <br />factor "K"), and the hydrologic classification. <br />3.1.1 Soil Classifications <br />• The site is located within Soil Mapping Unit Numbers 2, 5 and R (Permit Exhibit 2.6.6.A). Soil series of Map <br />Unit 2 is Fughes, Unit 5 is torri0uvent, and R is rock outcrop. Another "soil" type is identified in this <br />analysis: coal product. <br />3.1.2 Particle Size Distribution <br />Particle size distributions are presented in the following table. <br />Particle Size Distnbutiotu (- 4 mm fraction) <br />Size Sieve <br />(mm) :fi Finer (Pasting) By Weight <br /> Coal Product' <br />(SEDCAD+ Soil #1) Fughes= <br />(a silty loam, <br />SEDCAD+ Soil #2) Torrifluvent= <br />(alluvium, SEDCAD+ <br />Soil #3) <br />4.000 100 100 100 <br />2.000 80 99 99 <br />1.000 ti0 98 70 <br />0.500 46 96 67 <br />0.250 36 91 58 <br />. 2 <br />