2004-02-11_HYDROLOGY - M1977493 (3)

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/Y 3 arl" ) W. Ua. Wheeler and Associates, Inc. 1 Water Resources Engineers /ebruary 11, 2004 Mr. John G. Blair, P.E. Division 5 Dam Safety Engineer P.O. Box 396 Glenwood Springs, CO 81602 Re: #1051.18 /Robinson Lake Dam Outlet Inspection DAMID: 370107 Dear John: The purpose of this letter is to present the results of an inspection of the Robinson Lake low -level outlet that was performed on October 1,2003. We are in receipt of your Memorandum dated January 15, . 2003 and are in general concurrence with the information presented therein. An exception to this is the proposed operating limits for the reservoir, to which we would like to propose a modification, or clarification. This will be discussed later in this letter. The following is a summary of the results of the inspection. Present at the inspection were myself and Mr. Steve Jamieson of Wheeler, Mr. John Blair of the State Engineer's Office, and Jay Cupp and Tavis Rogers of Climax. Preparation for Inspection As a result of many years of operation as a process water storage impoundment, the low level outlet of Robinson Dam became inundated by several feet of sediment. As described in our August 5, 2003 letter to you, in order to inspect the low level outlet it was first necessary to remove the sediment from the area around the outlet. This was accomplished by lowering the water level in the reservoir to the level of the sediment and constructing a cofferdam around the outlet to isolate it from the main body of the reservoir. The cofferdam was constructed generally as planned, with a top elevation of approximately 10,843 feet. The configuration and general location of the cofferdam is shown on the attached drawing. The total height of the cofferdam was about 26 feet. After the cofferdam was complete in 3700 South Inca Street Englewood, Colorado 80110 (303) 761 -4130 FAX (303) 761 -2802