HYDRO31488

• Permit No: M1973021
• IBM Index Class Name: Hydrology
• Doc Date: 4/3/1975
• From: LEONARD RICE CONSULTING WATER ENGINEERS INC
• To: COOLEY GRAVEL CO
• Media Type: D
• Archive: No

- 9 -
velocity and is expected to move large rocks and other debris
' down the canyon. At the mouth of the canyon the channel is
not adequate for this flow and the floodwaters will travel
' overland to Bear Creek.
' DURING MINING
During the mining phase drainage is important to protect
' against damage to the operating area as well as downstream
property owners. There are two areas which must be considered:
the first is runoff and the erosion potential from the open
cut made by the mining operation; the second is floodwaters from
' the upper Strain Gulch tributary area which must be saf`.ely
passed through the operating level into the natural chernnel
' below in a manner that does not increase the magnitude of the
flood fro
it
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operation, as pointed out in the Thorne report, does not by
' itself appreciably increase the rate or volume of runoff.
Present Condition
At th
ti
f thi
i
e
me o
s report, quarry
ng operations i.n Strain
Gulch have been going on for five years by the Cooley Gravel
' Company. The status of the drainage features is described in
the following paragraphs.
' Because of the steep character of slopes in Strain Gulch
a fill has been placed along the lower 1600 feet of the gulch.
The operating area, including the crusher, stockpiles and other
necessary equipment, is located on this fill. The operating
area is below the actual quarry site and trucks transport
excavated material to the crusher where it is separated and
' stockpiled. At the east end, or mouth of the canyon, the
height of the fill is approximately 40 feet above the historic
' channel of Strain Gulch. A drainage conduit runs through the
fill f
rom the upper end near the beginning to the historic

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