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DRAFT <br /> <br />National Geodetic Survey, formerly the U.S. Coast and Geodetic Survey, as <br />benchmark S-257. The elevation for benchmark #2 if 874.43 as provided by the <br />Minnesota Department of Transportation Geodetic Unit. The water surface <br />elevation of Lake Orono was therefore approximately 871.83 feet (874.43 - 2.6 = <br />871.83) on May 5, 1970. <br /> <br />The 1996 survey references a gage located at the outlet dam on the southeastern <br />shore of Lake Orono. The elevation of Lake Orono is obtained by adding the <br />gage reading to elevation 870.0 as documented in the 1982 Operation and <br />Maintenance Manual for the Elk River Dam. The gage reading was documented <br />as being 2.2 feet on August 28, 1996. In reviewing this reading, it became <br />apparent that it was in error because a 2.2 foot gage reading represents 0.9 feet of <br />head above the weir crest at elevation 871.30. The resulting flow over the dam <br />would be approximately 360 cubic feet per second (cfs). <br /> <br />Q = 3.087 L (H)3/2 <br /> <br />L = 136 feet <br /> <br />H = 0.9 feet <br /> <br />Q = 358 cfs <br /> <br />The USGS flow record for the Elk River at ERCR 15 indicates flow between <br />66-111 cfs for a two week period around August 28, 1996 and 82 cfs on <br />August 28, 1996 (see Appendix E). In addition, the daily operations log for the <br />dam was obtained and it indicates a lake elevation reading of 871.6 which <br />corresponds to a gage reading of 1.6 feet (see Appendix F). The above gage <br />reading is consistent with the USGS flow record. <br /> <br />N :\059S\01 kELKRIVER. RPT-rlb 9 <br /> <br /> <br />