New Montello dam gate to be reinforced

The Montello City Council met in a special meeting last week to discuss the installation of one of the three gates in the newly repaired Montello City Dam which holds back the Montello River to form Montello Lake. The gate in question was installed according to a design approved by General Engineering, but as installed reduces its stress demand capabilities. Kent Fish and Svet Roussev, engineers with General Engineering, the Portage company that the city contracted with to manage this project, were present at the city council meeting.

There are two problems with one of three gates in the dam. First, the wheel was placed on the wrong side of the gate. Second, Fish admitted that General Engineering missed noticing that in review of the design drawings from the manufacturer of the gates that guide installation was not the correct one. He said, “A conflict in the shop drawing wasn’t caught.”

North American Hydro, the company that operates the electrical plant at the dam, expressed concern about the gate after its installation and its ability to withstand impact from debris, said Mayor Derek Krentz at last week’s meeting. They notified the city about that concern. The construction contractor notified General Engineering about the wheel placement. General Engineering had the contractor proceed to install the gate.

The wheel placement, Kent Fish told the City Council, is not a major concern and that this has happened on other dam projects. The gate manufacturer is working with the construction company to make the necessary changes to move the wheel at no additional cost. It does not affect the integrity of the gate. The guide concern, however, changes the calculations of stress load the gate can withstand. Fish said, however, that the installation as done did not put the engineering specifications out of the required stress calculations and he provided a copy of an email correspondence with William Sturtevant, Wisconsin DNR Dam Safety Engineer that said, “we concur with your acceptance of the shop drawings for the gates as revised.”

Because of staff changes, the DNR did not view or respond to the second design sent to them by General Engineering on 8-18-11, on which the altered gate was shown, the one in which General Engineering said they missed the conflict in the drawing.

On 8-22, General Engineering approved the design and told the gate manufacturer to proceed. After the concerns were expressed by North American Hydro and the City, on 12-16 General Engineering re-submitted the drawings to the DNR including one that has stiffening added to increase the stress calculations which would correct the error made in installation of the guides.

Mayor Derek Krentz at last week’s meeting, expressed concern over the strength of the gate because of that alteration and whether it could take impacts of debris even though the calculations are within the engineering requirements. The guide error reduced the stress calculation considerably from the original calculations from 10 times the requirements to 2.5 times, according to Fish.

Fish said repeatedly that even though the change in design lowered the stress calculation of that gate, the calculation was still within safety requirements. Council member Jeremy Kral said he did not feel comfortable that the original design was ten times the required strength and now the newly installed gate in question is only two times as strong as needed. “One is ideal, one not ideal,” he said. Council member Bob Knickerbocker questioned how the gate was installed, “knowing it was wrong,” without the city being notified.

Fish and Roussev handed out diagrams and showed two possible changes that will increase the stress load capacity on the gate in question. There are three changes that the city is requesting be done. First is moving the wheel from one side of the gate to the other. Second is an added gusset support. Both of these will be done by the manufacturer as part of the job. The third is a tubular support brace manufactured and installed at a cost of $2200. A discussion followed about who is responsible for the added cost. Krentz said, “I think the satisfaction of the city would be worth it to General Engineering that you need to find a way to pay.”

Jeremy Kral made a motion that passed that directed General Engineering to negotiate with the manufacturer of the gates on installation of brace at no cost to city.