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1 -lz- may reduce outflow considerations. Should a surface cl~~nnel drop be constructed for conveyance of the 15 to 20 cfs flow through the operating area down the east end fill during the mining operation, as shown in Figure 3, Alternative 2, it would be desirable to construct this channel to convey about 50 cfs and utilize it as part of the reclamation plan drainage facilities. SUMMARY The essential drainage features required for protection of the operating areas as well as to ensure no increased damage potential to downstream areas during the mining period has been defined as the following: 1. A sedimentation pond and flood detention area behind the access road embankment to the south quarry area. 2. An underground drainage system with an inlet upstream of the access road embankment capable of carrying the entire 100-year runoff from Strain Gulch. 3. Runoff from the quarry site should be directed into the detention area or facilities provided to either get it into the underground drainage system or provide for safe passage through the operating area to the east end of the fill. 4. At the east end of the operating area fill facilities are required to get the local runoff back into the historic channel of Strain Gulch without causing erosion of the fill slope. This can either be by open channel or pipe drop. The report also describes some consideration for drainage after the gravel mining is completed and the area is rehabili- tated. Since the operation is expected to continue over a period of 50 years, a definite drainage plan should not be established until an after-use plan is adopted. Assuming an after-use open space, the pits formed by the mining provide an excellent opportunity for detention reservoirs to provide increased protection to downstream areas. ~C1 Leonard Rice Consulting Watei Eny~neers.lnc.