SMITHLAND, KY: The U.S. Army Corps of Engineers has directed American Municipal Power, Inc. (AMP) to start flooding the cofferdam, constructed as part of the Smithland Hydroelectric Plant currently under development, as a result of historic flood forecasts and river levels above the 100 year flood elevation. The Corps made the request on Monday, May 2 after continuous rains and the backwater effect from the Mississippi River caused the flood forecast and the rate of rise to near the crest of the cofferdam.
Current river conditions at the Smithland Dam have not been experienced since 1937. On Tuesday, May 3, the river elevation was 344.04 feet and the cofferdam crest is at elevation 347 feet. The current elevation is just above the floodway of the cofferdam. Since implementing the emergency action plan, only an inch or two of water is flowing into the cofferdam and approximately 10 feet of water is presently pooled at the construction site.
The Ohio River is now projected to crest at Smithland at elevation 345 feet. This is a reduction of several feet from what was forecast on Monday, May 2. About one foot of water will be flowing into the cofferdam from the river through the floodway if the projection holds true.
If floodwaters hold at elevation 345 feet as predicted, only minimal damage to the cofferdam is expected. There will however be some delay as a result of the flooding and subsequent dewatering that will be required when river levels recede.
The floodway structure in the cofferdam is used to direct the flow of the river into the dam and allow flooding to occur in a controlled manner thus preventing serious damage to the structure of the cofferdam during significant flood events. The emergency action plan for flooding the cofferdam is required by the Corps of Engineers and the Federal Energy Regulatory Commission (FERC) and is a standard plan for all AMP hydro projects.
The decision by the Corps to open the Birds Point Levee (located on the Mississippi River near Wyatt, MO) has provided some relief on the flood levels at Smithland, prompting the revised crest forecast. The peak of the flood is expected to occur at 1:00 a.m. on May 5th at elevation 345 feet. AMP is monitoring the site closely, and working with our Builder’s Risk Insurers to determine whether we will meet the deductibles for claims under the flood insurance policy. The damages have to exceed 5 percent of the completed work or $1.75 million and 45 days of delay before the insurance coverage takes effect. We are tracking costs related to this event. AMP will also work with the contractor, CJ Mahan Construction, and engineer, MWH, to look at ways to make up the delay caused by this historic flood event.
AMP began construction on the 72 megawatt Smithland Hydroelectric Plant last summer. The project is part of AMP’s large run-of-the-river hydroelectric deployment – the largest such deployment in the nation. Six projects are being developed at existing dams on the Ohio River. The two other projects currently under construction at the Cannelton and Meldahl dams are not being impacted by the current high river levels. Construction is scheduled to start on a fourth project at the Willow Island Dam this spring.
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