2008-05-22_REVISION - C1980004 - Laserfiche WebLink

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Michael Boulay May 21.2008 necessary, usually when sediment reaches the 60 percent sediment level or when the pond is completely dry. The Pond will be certified annually by a Registered Colorado Professional Engineer and the Certification is then presented to the DRMS. There is a discharge permit in place for the old McClane pond so the operator will apply for a new discharge permit, or work to get the current permit amended in accordance with Rule 4.05.2(7). 20. DRMS: Statements on revised page 2-27i, indicate that the impoundment is located where serious property damage may occur. Therefore, in accordance with 4.05.9(2)(e)(ii), the pond should be designed to control the 100-year 24-hour event. Please provide revised design information which clearly demonstrates compliance with 4.05.9(2)(e). If the pond is a temporary impoundment it may rely primarily on storage to control the runoff from the design event specified in 4.05.9(2) (c). The demonstration should show how the water will be safely removed in accordance with current, prudent, engineering practices. CAM: In order to begin the design of the pond, the operator had to determine the Class of Dam, so the Operator referenced TR-60 and determined the Office Pond to be the lowest class, Class A. There does not appear to be any specific guidelines for design of Class A dams. Therefore, the Operator followed Rule 4.05.9(2)(b) which allows the pond to be designed to contain the 10-year event and safely pass the 25-year event (Rule 4.05.9(2)(c)). It appears that in order to possibly be required to design a dam to contain larger than the 10-year event, the Class of dam would need to be a Class B or Class, which the Office Pond clearly does not meet. It does not seem warranted for the office pond to be designed to contain the 100-year event. The Operator requests the Division read the text on page 2-27i which states failure ' The impoundment... is Class A because failure may cause minor damage to farm buildings, agricultural land, or township and county roads'; it does not state or insinuate that failure would cause serious property damage or loss of life. In addition, it is very unlikely that a dugout pond will have a catastrophic failure by the dam washing out, it is remotely possible, but highly unlikely. Therefore, the design was not altered, the Operator stands by the initial submittal of the Office Pond to be designed based on the 10-year event in accordance with Rule 4.05.9(2)(b). 21. DRMS: The primary spillway pipe on the proposed sediment pond extends to the channel of lower McClane Creek. 9