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along with the BB detour road in April 2010. The sedimentation ponds are designed, constructed <br />and maintained as follows: <br />a. Ponds 008, 009, 012, and 013 have been designed to contain the 25 -year, 24-hour <br />event with no discharge from the emergency spillway. Ponds 015, 016, and 018 <br />have been designed for a I00 -year, 24-hour event with no discharge. <br />b. The sedimentation ponds are designed to provide adequate sediment storage <br />volume in compliance with the DRMS regulations. The actual designs are based <br />on a minimum 3 year sediment volume based on USLE calculations. Actual <br />construction may cut more volume below the dam level (incised storage) to lessen <br />expensive cleanout during the operation. <br />c. The principal spillway design is typically an 18-24" diameter CMP or other pipe <br />which will have a valve on the entrance (see as -built for specific sizes). This pipe <br />will be stopped down in the inlet side to a 6" valve which will be controlled by a <br />wheel on the pond embankment. During normal conditions, the valve will be left <br />slightly open to provide 24-hour detention time for each pond during the large <br />events. This is accounted for as weep holes in the SEDCAD design runs. When a <br />large event occurs, the operator will wait until the Imhoff cone test shows that the <br />water meets effluent standards prior to discharge. If an Imhoff cone shows that the <br />water meets the effluent standard of 0.5m1 settleable solids per liter, the valve will <br />be opened until the water has dissipated to the valve level. It will then be left <br />slightly open to allow detention time for subsequent storms. For Ponds 008, 012 <br />and 013, SEDCAD analysis has shown that the effluent from a slightly open valve <br />still meets effluent requirements. For these ponds, the operator can decide to leave <br />the valve cracked or shut as described above. <br />d. Appropriate combinations of principal and emergency spillways to safely contain <br />or discharge the runoff from a 25 -year, 24-hour or larger precipitation events, as <br />required by the DRMS's regulations, will be installed. If a pond is designed to <br />contain the runoff from a 25 -year, 24-hour or larger event, an emergency spillway <br />will still be installed. <br />e. Pond freeboard will be a minimum of 1.0 feet from the highest level of water <br />allowed in the pond (or emergency spillway) to the top of dam. <br />f. The top of dam width will be at least 10 feet in all areas. <br />Section 2.05.3(3) Page 12 April 2017 (MR -104) <br />