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The amout of settling time actually required is a function of <br />the amount and size of the suspended solids in the water. <br />No formulas or mehtods of design are generally applicable. <br />. Some general design criteria for settling ponds are as follows <br />from "Civil Engineering Handbook" by Urquhart, page 10-65. <br />Period of Detention between 4 <br />Velocity of flow less than 1 <br />Depth of basin not to exceed <br />Ratio of Length to Width not <br />Width not greater than 40 ft. <br />VOLUME MINE WATER SETTLING <br />SETTLING TIME PROVIDED 80 <br />SETTLING TIME PROVIDED 237 <br />VELOCITY OF FLOW - FT/MIN <br />VELOCITY OF FLOW - FT/MIN <br />DEPTH - FT. <br />RATZO OF LENGTH TO WIDTH <br />WIDTH - FT. <br />and 12 hours. <br />ft/min <br />15 ft, preferably about 10 ft. <br />less than about 4:1. <br />POND (AF) 0.24 <br />GPM FLOW IN POND (HRS) 16.3 <br />GPM FLOW IN POND (HRS) 5.5 <br />80 GPM 0.10 <br />237 GPM 0.35 <br /> 6 <br />L=115' W=34' 3.4:1 <br /> 34 <br />The embankment around the pond is designed so runoff will not <br />enter the pond. The pond will only receive water which directly <br />falls into it in the form of precipitation and from the mine <br />dewatering system. The amount of water which enters the pond <br />in the form of precipitaion in considered insignificant. <br />The primary and emergency spillways will be designed to handle <br />the 237 gallon per minute flow. Two 6" diameter pipes will be <br />installed through the embankment. Neither pipe will be valved. <br />The outlet pipes will be installed so that the primary spillway's <br />l` flowline is 6" below the emergency spillway. <br />Calculate the flow though a 6" diameter pipe using the equation <br />Q = C*A*(2gh^0.5) where: <br />DSAMETER OF PIPE 6.000 INCHES <br />A = AREA OF PIPE 0.1963 SQUARE FEET <br />C = COEFFICIENT OF DISCHARGE 0.750 <br />H = HEAD ON ORIFICE 0.250 FEET <br /> <br />Q = 0.5906 CUBIC FEET PER SECOND <br />Q = 265 GALLONS PER MINUTE <br />The coefficient of discharge is for a tube projecting into <br />a body of water which is called a reentrant tube. The head <br />on the pipe is only 3 inches which assumes that the water level <br />is right at the top of the pipe. <br />Erosion protection will be provided where the pipes discharge into <br />Sanborn Creek. <br />• B-98 <br />