8/21/2007

Lake Red Rock Pool Drawdown this Fall

PELLA - In an ongoing effort to maintain a safe dam and conservation pool, a 10-foot pool drawdown to perform repairs and maintenance to Lake Red Rock's tainter gates and cables will occur the fall, beginning Sept. 4.

The current elevation of the conservation pool, 742 feet National Geodetic Vertical Datum, permanently submerges the tainter gates' cables and brackets. De-watering the tainter gate bays is necessary for repairs and replacement of the cables and associated equipment. Conservation pool is a term that refers to the minimum water level normally kept in the reservoir. The conservation pool varies through the year.

The fall drawdown will decrease recreational opportunities in the area through diminished sites or access for wildlife observation, waterfowl hunting and fishing. Preliminary analysis has determined that the lake will be accessible by boat ramp at elevation 732 feet NGVD. However, some ramp options may be limited by siltation, water depth and boat draft. Availability of the boat ramps for public use will be reassessed prior to, and during, the drawdown.

An Environmental Assessment with a Finding of No Significant Impact was completed in February 2005. The assessment evaluated the impacts associated with the proposed drawdown and replacement of the tainter gate lifting cables, as well as periodic inspection and maintenance of the dam. The Environmental Assessment is available on the Internet at: http://www2.mvr.usace.army.mil/Documents/
EA/RedRock/TainterGateCable/.  At the request of the Iowa Department of Natural Resources, the Corps evaluated and coordinated a 27-day extension of the original drawdown period, from 48 to 75 days. No objections to this extension were received.

During the drawdown, the Iowa DNR will be placing material to create fish habitat at several locations, and there will be work on a new boat ramp, access road and canoe launch at Elk Rock State Park. The Corps of Engineers will be doing minor repair work around the lake.

The lake will be lowered 0.5 feet per day, requiring approximately 20 days to complete the 10-foot drawdown. When repairs and construction activities are completed in mid-December, the pool will be raised as quickly as possible, while maintaining outflows of at least 300 cubic-feet-per-second. The total time for the drawdown, associated work, and reservoir refilling is approximately five months, although rainfall and snow amounts will greatly affect the total time to refill the lake. There must be at least 300 cubic-feet-per-second outflows to minimize impacts to communities downstream of the reservoir.

For more information, contact Frank Monfeli, project manager, at 309-794-5640 or Frank.C.Monfeli@usace.army.mil Or contact Sherri Richardson-Duey at Lake Red Rock at 641-828-7522 or Sherri.Richardson-Duey@usace.army.mil.