PERMFILE48640

• Permit No: C1981019
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: Sections 7-14
• Section_Exhibit Name: EXHIBIT 17 Haul Road PART 2
• Media Type: D
• Archive: No

-18-
Mr. Richard Atkinson
• May 14, 1981
Page Four
Using the disturbed area percentages as listed in the preceding tabulation
weighted CS values were ccmputed with the results being:
Streeter Gulch, CS = O.G92 x 8.656 + 0.013 x 91.4°6 = 0.020
Gulch A, CS = 0.092 x 15.456 + 0.013 x84.65'0 = 0.025
The Ade^yuacy Revievr also questioned the CR factor asking hour many diversions
vrere used in its computation. In our calculations we had used a P factor, the .
_ equivalent of the CR facto, of 1.0. This is the maximum value to f1e used fcr this
factor and corresponds to no diversions in the formula CR = 1 /(n+1)z.
Using the revised sediment delivery ratios and the vreichted CS fatter the 3-year
sediment yields have been reccmputed with the results cs follovrs:
Sedimentation Ponds
Taylor C-inch Str=eter Gulch \`Jork Lecdcut
Tributary Gulch A Area Area
Se~iment yield - 3 years
• ... ~evicwsly_ccm~ted (acre-feet) 0.92...... L.07 .. A.53 .. C.52 0.32
Sedia~: nt yield - 3 years
as revised (age-feet) 1.38 1 .66 1.17 0.62 0.74
Provided sediment
volume (acre-feet) 1.78(1) 1.85 1.26(2} 12.73 1 .04
(1} 1^Jith principal spillway elevation revised from 6938.0 to
6939.0. No other chances needed.
(2) With principal spillway elevation revised from 6614.0 to
6615.0. No other changes needed.
4. Sediment Clean-out; The Adequacy Report requires that ponds have a sediment
mar er installed at the 60°6 sediment storage volume (60'0 of the 3 year sediment
yield) elevetion. Vr~e concur with this requirement and the 60'.'o elevations are
as follows:
Sedimentation Pond
Taylor Gulch Tributary
Streeter Gulch
• Gulch A
York Area
Loadout Area
Elevations
Invert 60°.6 Vo . -100'6 Vo .
6935.0 6937.3 6938.4
6581.7 6583.2 6583.8
6611.0 6613.8 6614.8
7149.5 7149.7 7149.8
6381.0 6383.9 6384.7