It will cost nearly $2.5 million to repair the more than 100-year-old Bowersock Dam on the Kansas River.
More accurately, city leaders are hoping that it doesn’t cost any more than that.
Lawrence city commissioners at their meeting today are expected to hire a contractor for the repair job and authorize spending up to $2.45 million on the project.
After that, they’ll keep their fingers crossed.
“It will be a challenge,” said Chuck Soules, city director of public works. “It will be interesting to see what it looks like.”
No one has gotten a clear look at the face of the Bowersock Dam since 1978, when the state had that portion of the river relatively dry to build the downtown Kansas River bridges.
How much the dam has deteriorated in those 31 years isn’t known. But city leaders are undertaking the project after an engineering team with Black & Veatch wrote in a report that they were unable to “determine if the dam is in immediate danger of failing, as significant structural concerns exist.”
City engineers don’t wholeheartedly agree with that report, but regardless, the analysis has created concerns with the Federal Energy Regulatory Commission, which is the agency responsible for monitoring the dam.
“There are some areas where water is coming through the dam,” Soules said. “The dam has a wood truss structure underneath the concrete. If water is getting in there, the concern is the wood is rotting. If the wood rots, the concern is the concrete part of it will collapse.”
Regulators with FERC have ruled that the flashboards on the dam — which give the dam an extra 4 feet in height — can’t be raised until some repairs are made.
The city is funding the project by itself. The adjacent hydroelectric plant operated by the Bowersock Mills and Power Co. is dependent upon the dam, but company leaders have said they can’t afford to undertake the project. The city has deemed the project critical because without the dam, the water level in the river would not be adequate to efficiently operate the city’s Kaw Water Treatment Plant.
“The best way to see the challenge of losing the dam is to look downstream of the dam,” City Manager David Corliss said. “In many cases you see that it is a braided stream.”
Corliss said the project will be paid for through water rates. He said 2010 rates approved by the City Commission last month are adequate to cover the costs, although some maintenance projects in other parts of the community will have to be postponed to make the numbers work.
The project will create quite a sight for motorists on the Kansas River bridges. By mid-September a small work barge will be floating on the upstream side of the dam to drill holes — perhaps up to 50 feet deep — in the riverbed. Then a large crane with a special hammering device will drive sheet piling — a type of retaining wall — into the river.
The sheet piling will keep the area between the piling and the dam relatively dry while workers fill the area with rock, and then pour a concrete cap over the area in front of the dam. The new structure is designed to protect the face of the existing dam.
“We wanted to do it this way instead of opening the old dam up,” Soules said. “Nobody wants to do that. It is just a like a project at your house. If you start tearing into things, you’re bound to run into other issues.”
City leaders will hope for little rain during the project. High water levels on the project could cause more than $100,000 worth of rock and other materials to be washed away before the job is completed.
“It won’t just be the rain we get in Lawrence,” Soules said. “It can rain here all it wants, but if it rains a lot upstream, then that could be a problem.”
The project, which could take until January to complete, will involve work on only the northern two-thirds of the dam. Water will continue to flow over the southern end of the dam. Soules expects the project to add about 50 years of life to the dam.
Commissioners meet at 6:35 p.m. today at City Hall, Sixth and Massachusetts streets.