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8 <br />GCC RIO GRANDE -RED ROCK PLANT AND MINE <br />ARROYO DESIGN CRITERIA <br />1.0 Two basic shapes: <br />a Pazabolic Shape based on existing measurements (d = 3 to over 8', with <br />bottom widths from 10 to 30', top widths of 25 to over 50', and backslopes <br />from 20:1 to greater than 30:1. <br />b Broad shallow, somewhat "V" shaped. Approximated by 5 to 30' bottom <br />widths and side slopes from 20:1 to over 30:1. <br />2.0 Sheaz Force Limitations <br />Tractive force limits to establish slope limitations <br />a Assume water transporting silts. (Haan, p 114) <br />b Colloidal clay, haze soil, T = 0.46 psf, n =SCS Retazd "E", (Haan, p 114) <br />c Colloidal clay, poor vegetation, assume 0.5 as upper limit <br />d Cobbles, T = 1.1 psf, (Haan, p 114), n =based on Abt eqn. Use 0.8 psf to <br />account for rounded rock <br />e TRM (Pyramat, 2000 p~, unvegetated, long-teen performance, 40-hour <br />exposure, 4.5 psf (interpolated), nbased on SCS Retazd "E". <br />3.0 Velocity Limitations <br />Velocity limits also imposed, instead of Froude number. <br />a Assume water transporting silts. <br />b Colloidal clay, haze soil, V = 5.0 fps (Haan, p114) <br />c Cobbles, V = 5.5 fps (Haan p114). <br />d TRM (Pyramat 2000, p"n, unvegetated, long-term performance, 40-hour <br />exposure, V = 13 fps, <br />4.0 Design Frequency: <br />a Temporary diversion arroyos: remaining mine life with minimum of 10-yeaz, <br />no freeboad <br />b Permanent (applies to restored or relocated arroyos): 100-yeaz capacity with <br />one foot freeboazd. <br />1• <br />o6noroz <br />