Thousands of vehicles cross Bagnell Dam each week. It’s a means to an end for us and we give little thought to the engineering feat that took place 80 years ago that created the concrete structure that brought us to where we are today.


Thousands of vehicles cross Bagnell Dam each week. It’s a means to an end for us and we give little thought to the engineering feat that took place 80 years ago that created the concrete structure that brought us to where we are today.

Yet, there are engineers, consultants and specialists who have our livelihood and our safety in their best interests as they monitor the stability of the dam on a regular and detailed basis. One of those checkups comes next week when a local firm undertakes a survey of the dam to see if it has moved from its footprint.

Miller Companies of Osage Beach will conduct a Bagnell Dam Deformation Survey during overnight hours starting about 6 p.m. Monday and lasting several days. As a result, the westbound lane of the dam will be closed from 6 p.m. to 6 a.m. to accommodate the surveying work.

The surveying is part of a series of routine safety inspections conducted each year to verify the structural integrity of the dam, according to Alan Sullivan, consulting engineer at Ameren Missouri’s Osage Plant.

The structure is a concrete gravity dam that stays in place because of its size and weight. It was tied to the river bottom with footings when it was built in 1929-1930 and to the adjacent hills. But over its 80-year life, the federal government has established additional criteria to ensure its safety.

“With all of the pressures downward on the dam, from the forces under the dam, from the forces imposed by the lake behind the dam along with ice loads and wind loads, we’re required by the Federal Energy Regulatory Commission (FERC) to conduct these surveys every year,” Sullivan explained. “All of these forces might tend to make the dam move in one direction or another.”

Despite these enormous geophysical forces imposed on the dam, there has been no discernable movement of the structure during the last 22 years of testing.

“The survey is to see if there is any movement in the x-y-z (upward, downward and east-west) of the dam, to see if it has settled or moved,” Sullivan explained.

“There is no evidence that the stability of the dam has been compromised or anything to make us think the dam is unsafe,” Sullivan said.

The survey to be conducted by Miller Companies involves a series of established markers on the dam along with markers at land at each end of the structure not directly tied to the dam. As part of the five-year contract with Miller Surveying, the company is required to use the same equipment and same criteria in conducting the survey so an accurate comparison can be made. The contract also asks Miller Companies to research a more efficient, more contemporary system of measuring.

Rocky Miller of Miller Companies said the survey will involve three existing bases from which a micrometer and other surveying equipment will be used to site in locations along the dam and on the other side of the dam. Helping in the survey will be his father, Dale, who is retired now but is the founder of the company. Dale was involved in an early 1980s Bagnell Dam project that used a system of cables tied through the dam into the bedrock to add additional stability to the structure.

Sullivan said that in 1980-81, nearly 300 nine-inch holes were drilled through the dam some 100 feet into bedrock. Tensioned cables were then used to anchor the dam to the bedrock. As the cables adjusted, the holes were filled with concrete to provide additional stability.

Sullivan said FERC is now challenging Ameren to prove that the cables are doing their job.

“Ameren Missouri has lots of reasons to keep the dam safe,” Sullivan noted. “And we do all of these things the best that we can to make sure everyone is protected.”

Contact FOCUS Editor Dan Field at dan.field@lakemediaonline.com.