Lake Crystal Water Control Structure

The shallow lake habitat of Lake Crystal is maintained by a deteriorating outlet structure built about 1920. A new water control structure is proposed to 1) eliminate the threat of dam failure that would cause abrupt lowering of the water elevation of the shallow water habitat, 2) improve access to and maintenance of the outlet water control structure, and 3) allow for potential water level adjustments and temporary draw downs in the future to improve water quality and fisheries/wildlife habitat, consistent with MN Stat.103G.408. The existing structure is deteriorating. Observed structure deficiencies include: seeping where the dam ties into railroad embankment, cracking, spalling, and displaced concrete, undermining concrete on downstream side of the dam, and sackrete fill and patches on large section at the top of the dam. If not replaced the dam could fail and compromise water levels in the lake. The sport fish community of the lake consists of black crappie, white crappie, northern pike, walleye, channel catfish, bluegill, and yellow perch. The walleye population is maintained through stocking. The lake outlet is located in an area of the lake bordered by MN Hwy 60. The outlet passes beneath both Hwy 60 and railroad right-of-ways. The existing structure is located between the highway and railroad. The lake outlet flows north through three, 115-inch diameter culverts into a small pond on the north side of Hwy 60. A 140-foot wide, low-head dam within the pond controls the elevation of the lake. From the dam, water flows under a railroad bridge through a ditch to Minneopa Creek. Maintenance of the existing structure has been challenging as it is located on railroad right-of-way between a four-lane highway and railroad. The new water control structure will be downstream of the existing structure just north of the railroad. Access to the site will be from City-owned property, greatly improving access for construction and maintenance of the new structure. The new structure will be a variable-crest water control structure to allow for managing water levels to improve fish/wildlife habitat by increasing rooted aquatic vegetation and water clarity. A drawdown is not planned at this time, but when determined to be in the public interest, with notification of all riparian landowners, a public hearing, permission of 75% of riparian landowners, and other provisions consistent with MN Stat. 103G.408, a drawdown will be possible.