(Updated: 10/14/02)

	Doug Walter/NENA
	The weir moderating the lake's outward flow on 10/13/02. Although still high, the creek's water level has subsided enough to allow the automatic mechanism to start lowering the lake's overly high water level.

The weir, or dam, at the outlet of Lake Nokomis where it joins Minnehaha Creek is being repaired after several months of problems. Heavy rains this past year have helped set an all-time high water level at Lake Minnetonka, the source of Minnehaha Creek at Gray's Bay. The resulting high water flow in Minnehaha creek strained the automatic mechanism of the adjustable weir at Nokomis, already hindered by a malfunctioning gasket on the air compressor that raises and lowers the weir.

The weir, completed in February of 2001, was designed to prevent Minnehaha Creek from flowing into Lake Nokomis during storm events, preventing the inflow of rough fish and pollutants, primarily rain water runoff from upstream streets and lawns. As part of the project, the lake's carp population was reduced in January, 2001.

Still within a planned two-year testing phase, the weir was engineered to rise and fall automatically with fluctuating water levels using an underwater, inflatable bladder. Because the automatic control system had failed, an engineer had been manually working the mechanism until repairs could be made. However, during the creek's dangerously high flow of 350 cubic feet per second in mid-September, a gasket on the air compressor that inflated the bladder failed. Subsequent periods of high water in the creek spilled over the top of the weir, allowing the creek to backflow into the lake for short periods. Several alert residents had noticed the backflow and called NENA, the Park Board, and the Minnehaha Creek Watershed District (MCWD).

Doug Walter/NENA
The underside of the extended weir showing the inflated bladders on 9/30/02.

City maintenance staff and engineers from HDR, the engineering firm hired to supervise the contractors involved, repaired the compressor on Thursday, Sept. 26. (See photos, below.) HDR mechanical and electrical engineers performed a complete review of the system and documented needed repairs and maintenance. HDR believes that most of the bugs in the mechanism have been discovered and that operation should dramatically improve during the second year of operation.

The weir is just one part of a much larger Lake Nokomis water quality restoration program, originally conceived by the Blue Water Commision, a multi-neighborhood coalition initiated by NENA's Environmental Task Force. NENA won the Best Environmental Project award in 2001 from the Neighborhood Revitalization Program (NRP) for their volunteer efforts. The restoration was brought to fruition by the Blue Water Partnership, consisting of the City, the Park Board, and the MCWD who monitored the construction and continues to maintain stewardship for water quality along the creek and in the lake.

Tony Luft/HDR

Lakeside of the extended weir showing the lake's water being dammed during the repair on 9/26/02. The stone building at top houses the compressor and electrical cabinet.

Doug Walter, NENA.

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