August 25, 2014 Share

Engineers: Wolf Creek Dam repairs ‘permanent

There are more indications that engineers at the Nashville District of the U.S. Army Corps of Engineers are confident the seven-year, $594 million rehabilitation of Wolf Creek Dam is a permanent fix for the oft-troubled earthen and concrete structure that impounds Lake Cumberland.

First and most visible sign of confidence in the project: Safety reviews were good and the lake, 40 feet below normal for six years, was allowed to rise 25 feet during Summer 2013 and then to normal pool stage at the tree line during vacation season this summer.

Secondly, unseen by the public, is less on-site hourly inspections of the dam. Live person monitoring of the dam has been reduced two-thirds; from 24 hours a day to eight hours a day.

Monitoring the dam in person means walking the length of the dam to make sure there are no problems. During more than seven years when the dam was in crisis mode, an engineer inspected the mile-long structure every hour, 24 hours a day. Now, the inspections are done only eight hours each day.

An outside panel of experts declared the dam in “high risk” of failure. The Corps announced in August 2005 that a complete rehabilitation of the dam was necessary.

If Wolf Creek Dam had failed, communities downstream to Nashville would have been seriously flooded. The situation was so serious radios with an emergency frequency were provided to residents below the dam. Maps were drawn showing high water levels along the Cumberland River in case of dam failure.

Wolf Creek Dam, during rehabilitation, was the most monitored dam in the world. Up to 300 instruments were installed in the structure to automatically monitor both earth and water movements. Some would send electronic warnings to Nashville District headquarters in case a threshold was exceeded. All this was in addition to the aforementioned engineers eyeballing the structure hourly, 24 hours a day.

Once, while drilling in Critical Area 1 near the juncture of the earthen and concrete sections of the dam, movement of earth deep inside the dam forced work to halt in that area. The shifting created such a scare public safety officials downstream were notified.

Caverns in limestone rock beneath the dam caused uncontrolled seepage that undermined the integrity of the dam. The area near the concrete monolith was laced with caverns and determining a safe drilling method eventually delayed the rehabilitation project for a year.

Don Getty, project manager, said about 50 automated monitoring instruments remain in the dam, some of which will signal the Nashville headquarters if there is a problem.

The permanent fix was accomplished by inserting a concrete wall, 4,000 feet long, 275 feet deep and a minimum of two feet thick, through the earthen section of the dam. The wall extends up to 100 feet into the base of the dam, terminating in a more stable limestone stratum.

Work is still going on at the dam. A site stabilization contract was let August 11 to Aspen Construction, a Minnesota-based firm, that, among other things, will assist U.S. and Kentucky fish and wildlife services in creating a new Hatchery Creek. Dirt removed from digging the channel for a mile-long trout fishing creek will be used by the Corps to fill a low place below Wolf Creek Dam and provide soil to stabilize a 40-acre disposal area used during the dam rehabilitation project.

This coming winter, a road restoration contract will be let to realign the intersection of the road leading off U.S. 127 to Kendall Recreation Area and Wolf Creek Dam National Fish Hatchery. The realignment, to be done next spring and summer, will make it easier for boats and trailers to turn off and onto U.S. 127, Getty said.

Also, the contractor will uncover and make usable an old boat ramp at the former Halcomb’s Landing. A new Halcomb’s Landing with boat ramp was built while the dam was being repaired.

Restoration on the face of the dam is complete, Getty said. The 75-foot-wide work platform, base for heavy drilling equipment inserting the concrete barrier wall, has been reduced to a permanent 30-foot-wide access road across the upstream side of the dam.

In other lake news, Getty said the Corps this fall will monitor duskytail darters in the Big South River “ … to see how (the darters) are doing.”

The U.S. Fish and Wildlife Service plans to remove 10 to 20 pairs of duskytail darters from the Big South Fork River and take the minnows to Conservation Fisheries Inc., a non-profit company in Knoxville that has developed techniques to propagate the region’s rarest fishes. Progeny of breeding duskytail darters at Conservation Fisheries will then be moved to Wolf Creek Dam National Fish Hatchery for safekeeping.

Duskytail darters became infamous for threatening to keep Lake Cumberland about 18 feet below pool stage this summer after the federally protected minnows were discovered in the Big South Fork at the headwaters of the lake. The minnows took up new habitat in a five-mile stretch of Big South Fork River while Lake Cumberland was kept low for seven years during repairs to Wolf Creek Dam.

A normal lake at pool stage would push still water over newly claimed habitat of duskytail darters and sediment would eventually destroy the habitat. The situation resulted in an announcement late this past spring that Lake Cumberland would remain at about 705 feet above sea level this summer to protect the 2 1/2-inch-long minnows.

 

The announcement created a firestorm of protests from tourism interests who expected a full lake after repairs to Wolf Creek Dam had been completed. The controversy reached Congress and Senators Mitch McConnell and Rand Paul, both of Kentucky, Senator Lamar Alexander of Tennessee and Somerset’s Congressman Hal Rogers met with heads of the U.S. Fish and Wildlife Service and U.S. Army Corps of Engineers in McConnell’s Washington office and hammered out a quick solution to the problem. The quick solution was to seine a few duskytail darters out of the Big South Fork River for propagating and safekeeping and let the lake return to normal levels.

Removal of the minnows from Big South Fork has to wait until the lake through normal operation in late summer and fall reaches a level sufficiently low to retrieve the minnows. Thursday, the lake was about 13 feet below the tree line.

BY BILL MARDIS
COMMONWEALTH JOURNAL
FULL STORY

 

 

Admin