HYDRO24993 - Laserfiche WebLink

Home Browse Search

DESIGN DISCHARGES AND VOLUMES Basin 100yr-24hr Peak Discharge 25yr-24hr Peak Discharge IOyr-24hr Volume East Basin 5.9 cfs ----- ----- West Basin 4.6 cfs ----- ----- Fast Pond, Yard ----- inflow 0.4 cfs outflow 0.0 cfs 0.19 AF West Pond, Yard ----- inflow 2.5 cfs outflow 2.4 cfs 0.98 AF West Hillslope 0.9 cfs ----- 5.2 Yard Drainage Routed to Ponds Reach 6 drains the West Hillside drainage area. The channel is trapezoidal in shape with a depth ranging from about 15 inches in the upper reach and over 20 inches in the lower reach. The bottom width varies from 1 ft to 2 ft and the side slopes are generally 2:1. The channel invert slopes are approximately 0.0111 fdit and 0.0600 ft/ft for the upper and lower reaches respectively. The channel bottom is broken rock and dirt with a moderate to heavy grass lining which appears to protect it from erosion. Normal depth flow capacity is approximately 7 cfs for the upper reach and up to 60 cfs for the steep lower reach. Critical flow will probably occur on these slopes resulting in a reduction of the flow depth and a further increase in the channel's capacity. A minimum design geometry for the ditch would include a trapezoidal or neaz trapezoidal shape with a 1 ft bottom width, approximately 2:1 side slopes and a 1 ft. depth. This would supply more than adequate capacity and freeboard for the design flows. There aze no signs of erosion in the existing ditch and since it has been in operation for many years there is no need for tiprap channel protection. At the bottom of the hillslope the ditch, reach 6, is intercepted by a 24" corrugated metal pipe, reach 9, which is at a slope of 0.044 fUft. The normal depth flowing full capacity of this pipe is 21 cfs. Reach 7 is an existing a 36" reinforced concrete pipe, RCP, which traverses the mine yard. It provides site drainage for portions of the mine yazd. It begins with a drain inlet located below the conveyor belt near the center of the yard and extends to the north with inlets across from the shower house and in front of the sales office. It then turns and passes under the main access road where it empties into a large ditch which flows into the West Sediment Pond. The culvert is about half full with sediment. The Flowing full capacity without sediment is 97 cfs and with half the barrel full of sediment the capacity is reduced to 35 cfs. The culvert capacity is more ~~ 6 June 1995