Lake Sakakawea

by kfrego

Lake Sakakawea is the reservoir behind Garrison Dam on the Missouri River in North Dakota. The lake has 1320 miles of shoreline, is 178 miles long, and is up to 180 feet deep. It’s one of the best northern pike and walleye fishing locations in the country.

Gates and Fox negotiated a target estimate agreement on a partially completed project just north of Beulah, North Dakota. The project consisted of an onshore shaft and pump station, 3400 feet of segment lined tunnel, and an offshore shaft on Lake Sakakawea. The previous contractor had numerous problems with the project. The project owners removed the contractor and rebid the remaining work. When we arrived on site in May of 1982 the on shore shaft was excavated to grade and tunnel excavation was started. The twenty foot off shore shaft cofferdam was installed and an eight foot diameter steel liner had been installed through 80 feet of water and driven to refusal in the bottom of the lake bed. In order to prevent damage from ice during the winter the cofferdam had been removed and 25 feet had been cut off the steel liner of the shaft. All off shore equipment had been demobilized for the winter. There wasn’t a tree within several miles of the job site. The project when completed would supply water for a large coal gasification plant under construction a few miles away.

Jim Lewis was our project manager. Gene Creech from Downsville,NY was brought in to act as our offshore operations manager to reinstall the cofferdam and shaft liner. Gene worked on the submittals of work plans while designing a neoprene seal system to be installed on the steel shaft liner section which had been removed. Myself and Gene had the chore of locating the submerged shaft under 25 feet of water. This was before GPS and cell phones that could follow you anywhere you went.

We studied the shoreline contours in relation to the underwater shaft location. Our project surveyor established some reference points with flagged poles which we could see while searching for the location on the lake. We then resorted to old style, accurate methods, with a long history of success in underwater searches. We had a rope with a concrete block on it which was trolled back and forth from an aluminum boat. It sounds pretty simple, but when you’re a over half mile from shore trying to triangulate on a couple flags, an eight foot target can get pretty elusive. Needless to say we spent a considerable amount of hours until we heard the resounding clunk. We immediately dropped our sophisticated buoy marker. An empty blue one gallon Chevron Delo 400 oil jug with a sealed lid on a separate rope. Once we had the first bouy it was easy to finalize the location and get several bouys for reference. Our crews on shore were fabricating the seal on the steel shaft liner, mobilizing the barges, crane, tugboat, and other off shore equipment.

We didn’t get too fancy on underwater shaft locating equipment,,,,,,,,but we were stubborn enough to get the job done.

 

 

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