The intake structure, located on the Lake Sakakawea side of Garrison Dam, just above the Garrison Dam power plant, became operational in 1956. Water from Lake Sakakawea flows through 10 gates at the intake structure and then channeled into five 24-foot tubes, or penstocks, that supply water to the electricity generating turbines at the power plant on the opposite side of the dam.

Both bulkhead gates and penstock gates are important components in the operation of the intake structure. The bulkhead gates are situated on the water side of Lake Sakakawea. Since 1956 they’ve been lowered to the top of the penstocks, but have never been lowered to full closure.

The huge gates are 12 feet wide, 26 feet tall, and 50 tons each in weight. They are, essentially, a protective barrier should they be needed in the event of a problem that would necessitate the shutting down of water entering the penstocks.

“The gates remain in the water, 150 down, right above the tunnels,” explained Loren Nishek, U.S. Army Corps of Engineers project engineer. “If the penstock tube would ever break, we could release the gates and stop the water from going through. That’s the purpose of these gates, to control the water through the penstocks.”

Kim Fundingsland/MDN Leeann Wimer, U.S. Army Corps of Engineers mechanical engineer, looks out over the open water of Lake Sakakawea from the observation deck at the Garrison Dam intake structure, shown in this Jan. 13, photo.

On the main floor of the intake structure huge dials above the bulkhead gates, numbered from zero to 170 feet, have needles pointing to the location of each gate.

“Right now we’re probably 30 feet above the water level,” remarked Nishek while on the main floor during a tour of the intake structure on Jan. 13.

Looks can be deceiving, especially for the tallest structure in the state. Most of the intake structure is hidden beneath the water Lake Sakakawea. It is 249 feet high, several feet taller than the 18-story State Capitol building in Bismarck which is recognized as the tallest building in the state.

Workers had to use powerful overhead cranes to remove the bulkhead gates so that crews could work on them. A special vinyl paint, white, was chosen so that any future damage to the bulkheads would be easier to see than if a darker color was used.

“They were last repainted in the mid-90s time frame,” said Leeann Wimer, USACE mechanical engineer. “What’s happening now is a planned rehab on these gates so they will last a few years longer. These gates are getting a new paint job, some weld inspections, repairs as needed, new guides on the sides and roller chains are getting rehabbed.”

Nishek said the warm winter weather has made it much easier than a year ago when cold temperatures created some problems, especially when huge pieces of equipment had to be transported outside during certain phases of the project.

“Mother Nature has been unbelievable,” said Nishek. “Last year we couldn’t get equipment started because it was so cold. This year is no problem.”

Most of the work now is being done indoors, utilizing an extensive ventilation system. The project remains on schedule with the last gate receiving new paint in mid-January.

“There’s always glitches but we seem to work through them and move on,” remarked Nishek. “We hope to be done, clean up the mess, and out of here Feb. 13.”