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1. The lake outlines on the two surveys were drawn from two different aerial photographs taken 28 years apart. The later survey omitted the very shallow upper portion of the lake; as a result the areas were approximately 10 percent different, and the lake outlines between the two surveys varied and could not be directly compared. During the analysis, the volumetric comparison was based on only the lake area included in both surveys and does not include lake area upstream of the limits of the 1996 survey. To normalize the lake outline differences, the 1996 lake outline was utilized due to its higher level of detail. 2. The two lake surveys do not reference the same benchmarks. The survey benchmarks were investigated and the surveys adjusted to account for the varying lake elevations on the two survey dates. Benchmarks referenced in both surveys were surveyed together and it was confirmed that their relative elevations are correct. The 1970 survey references two benchmarks. Benchmark #2 is a brass monument on top of the concrete wingwall on the south side of the Lake Orono • Dam west of Main Street. The benchmark was established in 1970 by the National Geodetic Survey, formerly the U.S. Coast and Geodetic Survey, as benchmark S-257. The elevation for benchmark #2 if 874.43 as provided by the Minnesota Department of Transportation Geodetic Unit. The water surface elevation of Lake Orono was therefore approximately 871.83 feet (874.43 - 2.6 = 871.83) on May 5, 1970. The 1996 survey references a gage located at the outlet dam on the southeastern shore of Lake Orono. The elevation of Lake Orono is obtained by adding the gage reading to elevation 870.0 as documented in the 1982 Operation and Maintenance Manual for the Elk River Dam. The gage reading was documented as being 2.2 feet on August 28, 1996. In reviewing this reading, it became apparent that it was in error because a 2.2 foot gage reading represents 0.9 feet of i N\0596 W I\ELY.RI VER.RPT-NCW 8