2013-11-27_REVISION - M1990057 - Laserfiche WebLink

Home Browse Search

Mr. Michael Cunningham CDRMS November 26, 2013 diversions, and vegetative filters for overland flow discharges. All areas disturbed by construction will be temporarily re- vegetated or graveled and maintained as soon as practical. (1) Nature of Milling Activities at the Site The Mill is a custom ore processing facility. Ore will be routinely delivered to the facility. Ore will be processed at a maximum production rate of 200 tons per day. Ore will be conveyed to the crusher, then through a series of processes to produce concentrates. These concentrates will be shipped off site for further processing. The process tailings will be pumped to a CDRMS approved TSF. The TSF is located adjacent to the Mill. The Mill will be operated and or maintained 365 days a year -24 hours a day, 7 days a week. (2) Design Parameters Once the CDRMS permit is issued, the following construction activities will commence. Based on- Wilkes, S.G and Erke C. King, 1975. Procedures for Determining Peak Flows in Colorado— Soil Conservation Service: Install BMPs on access road from Highway 24; Install or repair other BMP structures; Improve or construct structures on the preexisting access road including berms, swales, debris basins, and ditches using the following design criteria and methods; • Drainage Area: 20.7 acres (entire property). • Runoff Coefficients. Undisturbed forest Runoff Coefficient Number (RCN) = 60. • 10-yr,and 100 -yr 24hr Stormwater Events. The estimated peak flows from the 10 -year, 24 -hour (0.54cfs) and 100 -year, 24 -hour storm event (3.Ocfs) are presented in Attachment 7. The peak flows were calculated assuming a RCN =60, a drainage area of 20.7ac, the disturbed area is internally drained, Lodgepole Pine vegetative coverage is approximately 40 %. • Drainage Channel Configuration (Stormwater Diversion). Stormwater for the 100 -year, 24 -hour storm event of 4.25cfs will be conveyed around the disturbed area in a ditch that has 1:1 side slopes that is at least 1.25ft deep constructed on a slope less than 5 %. The drainage basin configuration, flow estimates and assumptions are presented in Attachment 7. Existing 12in culverts will convey the peak flow from the 100 - year -24 -hour storm with a flow through velocity estimated to be approximately 8.Ofps. o Affected Area: (Estimate of total affected area, and area /location expected to be disturbed by clearing, excavation, grading or other construction activities). • The mill permit area occupies approximately 10.Oac; • The TSF occupies an area approximately 3.Oac;