Poking holes in the dam: Corps to announce lake level in February
Work on the platform resumed after the holiday break. On the pad are grout plants like the large object at right, sonic drilling rigs (in the center in the distance) and grout injection equipment at right behind the pickup truck. The wall to be installed in the dam will be placed between the two lines of orange pipes running the length of the work platform.
In Jan. 10-16, 2008 issue
By Greg Wells, Times Journal Managing Editor
WOLF CREEK DAM - The decision on whether to raise the level of Lake Cumberland to 690 feet above sea level in the coming season will not be made until sometime late this February, according to the project manager for the repairs to Wolf Creek Dam.
That would be 10 feet higher than the level supported during 2007.
David Hendrickson, who works out of the US Army Corps of Engineers' District office in Nashville, said it will take that long to finish the first line of grouting on the dam and study the necessary data.
That first line, on the side of the dam closest to the lake, will have holes drilled and pressure filled with a very slick concrete substance at least every five feet for the entire length of the work platform.
Hendrickson said that work is progressing well and that the second line of grout holes is also in the process of being drilled down to a level below the target for the planned wall which will go between the two lines of grout.
The contractors who will be submitting bids and proposals for constructing that wall had been called to a meeting at the dam this Wednesday to get one final look at the project before submitting their proposals.
Geologic data from special exploratory wells drilled in the path of the wall and other information will be presented to them before they begin the final preparations to submit their bids, explained one of the engineers on-site, Kim Warner.
Meanwhile the drilling and grouting has returned to around-the-clock work as the Corps closely monitors the instruments in the dam to analyze the amount of seepage that is still occurring.
Warner said that seepage has been markedly reduced, but tempered that comment with the observation "this has also been one of the driest summers and falls on record."
After a tour of the work platform, she pointed out walls full of data regarding the pressure testing and grout intake of all the holes. The data hangs in the conference room of the recently completed construction headquarters below the dam.
Warner used them to illustrate the problem they had expected, the large intake of grout at the area referred to as the "wrap-around" where the concrete dam ends inside the earthen portion of the dam.
The engineer pointed out that though the first of the holes took a large amount of grout the later holes in the same area, where they had known caves existed took progressively less grout.
Warner explained that the schedule for the grouting first called for the holes to be 20 feet apart, then to divide the distance between each whole once and then a second time yielding a wall of grout holes 5 feet apart all along the both sides of the wall, before it is installed.
The engineer added that the distance could be divided again for holes that are just over 2 feet apart, and that in the wrap-around area another line of holes on the platform further toward the lake has been added to improve the seal inside the voids in the bedrock in that area.
As the contractors work to complete the first line of grout, and progress with the second, the next set of contractors will be making their decisions on what they feel is the best method for installing the wall within the earthen dam down from the platform all the way into a deeper layer of bedrock.
Project Manager David Hendrickson said the proposals for how to install the wall and how much it will cost will be finished by early March and by mid-May the decision on the best method, and therefore who has won the contract should be made.
The two most likely methods to be proposed, Hendrickson said, are one which involves drilling a line of bore holes which are shaped to interlock; or another that cuts a line of 2-foot wide by 6-foot long columns down to depth and a second set filling in the dotted line, interlocking them.
In either case the new wall is designed to penetrate to harder rock below the cave-prone limestone that much of the present seepage is moving through.
Warner said the grouting has proceeded apace and that even with the time off for the holidays they are on schedule.
All 50 of the grout holes presently scheduled inside the dam have been completed and filled, Warner said.
She said that it is anticipated that further grouting will be approved inside the gallery, extending from the coverage completed from the earthen end to well beyond the wrap-around in front of the concrete monolith portion of the mile-long dam.
It has been reported before that the corps has been considering grouting all the way to the far wall inside the dam.
Warner said the Corps has no evidence of any seepage below the concrete section of the dam, but they may take this step as insurance while they are working on the dam.
In this week's progress report she notes as well that the work on the bathhouse / laundry in the Corps' Kendall Campground below the dam is under construction and the foundation and slab were poured this week.
The new access road below the dam has been completed as well but has not opened to the public as it is to be used for a haul-road for contractor working on the dam wall.
Warner said public access to the Wolf Creek National Fish Hatchery and both campgrounds is likely to remain the same road that was installed when the dam was completed.
She added that the new ramp at Halcomb's Landing is finished, and the new access to it, along with the parking has all been paved and striped. A comfort station is also operational at the launch ramp.
At the same time, work has also progressed on the generators in the powerhouse of the dam.
Larry Brown, who has been supervising that project, said generator number 6 has been rebuilt and returned to service while they are moving forward now with taking down and rebuilding number 4.
The huge turbine electrical generators are over 50 years old, having been in operation since the dam's powerhouse was completed.
He explained that the recent news releases regarding the powerhouses here -- as well as at Center Hill and Dale Hollow dams in Tennessee located on Cumberland River tributaries -- are announcing studies on increasing the possible output of the generators.
Brown said they can presently put out no more than about 50 megawatts per turbine but with changes to the generators, turbines and the switching gear at the powerhouse could allow as much as 70 megawatts per unit.
But those changes are some time off. He said the Corps is simply at the point of accepting public comment on the proposal.
The next news anticipated about the lake is the announcement regarding the water level this coming tourism season.
When pressed about the progress and the possible news that the lake level could come up as much as 10 feet this spring, Hendrickson said "Indicators are currently positive."
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