PERMFILE104930

• Permit No: M2000113
• IBM Index Class Name: Permit File
• Doc Date: 8/17/2001
• Doc Name: DRAINAGE STUDY ROARING FORK RESOURCES INC MAMM CREEK SAND & GRAVEL PIT
• Media Type: D
• Archive: No

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4. Runoff from the portion of the I-70 corridor that discharges into the Dry Creek
mining azea is calculated using the Rational method and is estimated to be.
Area Existing Condition Runoff, cfs
Acres 10 yr-24hr 25 yr-24hr ~ 100 yr-24hr
33.68 29.98 36.87 ~ 40.60
5. The runoff for the each mining and the surface facility areas was calculated using
the SCS TR-55 Method and is estimated to be:
~ Existing Condition Runoff, cfs Developed Condition Runoff, cfs
Area ~ 10 yr-24hr 25 yr-24hr 100 yr-24hr~ 10 yr-24hr 25 yr-24hr;100 yr-24
West End 4.00 8.13 12.49 ~ 11.39 18.30 25.83
,
Dry Creek ~ 1.64 3.44 5.56 7.80 I 18.12
12.71
Slough to East
Property Line 2.48 5.60 9.37 14.04 22.50 j 31.51
West Property Line to
Horse Fence 3.27 7.19 12.26 19.86 30.52 43.03
Surface Facility (no
Pit) I 1.83 3.63 SS2 5.67 9.37 li.51
6. Sediment and erosion control for the pits is expected to be provide by in pit
detention areas that would also be utilized to dew~ater sections of the pits as
required.

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7. The sediment and erosion control for the Dry Creek surface facility area prior to
the area being mined for gravel is provided by road borrow ditches and a
detention pond. When the Dry Creek area is mined, the detention pond will be
removed and the surface runoff will be directed to the in pit detention azea. (See
Exhibit SF-1)
8. The size of the road borrow ditch that directs the surface facility runoff to the
detention pond is:
Description Feet
Bottom of Ditch 2.00
Depth of Flow 0.78
Ditch Width -Top of Flow 5.90
Ditch Width -Top of Ditch 7.40
Freeboard 0.30
Ditch Side Slope 2.5:1
Velocity, fps 3.2
The ditch should be lined with riprap with a D,o = 6 inches. The dimensions
above are inside dimensions from the riprap surface. An alternate erosion control
method would be the use of check dams on 150 feet centers.