July session of “Let’s Talk Bridges” describes the effects of high water on construction work
Diagram depicts “out in space” construction process on new bridge ... The diagram above shows the “erection sequence” for the new bridge, including the final section that will be floated down the river into place before being elevated to complete its final connection. The truss elements to the immediate left and right of that final float-in section will be left extending out over the river awaiting that final section in an “out in space” construction process further described in the accompanying article. Image courtesy of HNTB Corporation Project Manager Travis Konda.
Air lift pump demonstration ... Travis Konda, project manager, HNTB Corporation put together and demonstrated for attendees a miniature air lift pump. The demonstration pump was made from 3/4” copper pipe for the exit pipe and a 3/8” copper pipe for the compressed air supply feed. It is approximately two feet long, designed around a five-gallon pail for demonstration purposes. The actual air lift on the bridge project site is 10” diameter and approximately 150 feet long. Air lifts are generally used to clean the created hole whenever drilled shaft construction “in the wet” (meaning there is water in the hole) is conducted. Photo by Julie Berg-Raymond.
by Julie Berg-Raymond
The July session of “Let’s Talk Bridges!” (held Thursday, July 11, at Meehan Memorial Lansing Public Library) was a little shorter than the usual hour-long presentation regular attendees look forward to every month. There wasn’t a lot to talk about by way of progress on the bridge - crews with Kraemer North America, the contractors building the new bridge, haven’t been on the river since mid-June because of high water.
Pete Hjelmstad - FAA-licensed drone pilot and public media coordinator with the Iowa Department of Transportation (DOT) - has been taking aerial photographs of the work sites, though; and Clayton Burke - project manager with the Iowa DOT - showed attendees some of those photographs during the July 11 session and explained how the rising waters have affected work on the new bridge. Burke was accompanied that evening by two other members of the “bridge talk team” - Anden Lovig, construction engineer; and Travis Konda, project manager, HNTB Corporation.
THE TALKS
The monthly bridge talks are a joint effort of Project Manager Clayton Burke with the Iowa Department of Transportation and Meehan Memorial Lansing Public Library’s Executive Director Derva Burke. The talks are held the second Thursday of each month at the library from 5 to 6 p.m. and are presented as an opportunity for attendees to have questions answered, and to learn about the new bridge project from engineers who are working on the project. Each session generally involves a project update (with visuals), a question-and-answer session, and an activity or demonstration.
While the bridge talk sessions can be watched in real time or viewed later on the library’s Facebook page at “Meehan Memorial Lansing Public Library,” being at the monthly talks in person allows attendees to engage one-on-one with the experts who are working on this historic project, and to gather with other community members as the work progresses.
“It means a lot to us that you’re here, to listen to us talk about the bridge and show off some of the things we’re really proud of,” Burke told attendees at the July session.
PHOTOS: RIVER LEVEL EFFECTS
Showing a series of aerial photographs taken from videos made by Pete Hjelmstad, Clayton Burke explained what was happening at various river levels. At 12.89 feet, he said, “the constructed piers were starting to go underwater.” They tried to pump water out of the cofferdam but they couldn’t keep up with it; so they decided to wait for the water to go down. “But,” he said, “it came up to 14 feet.” At 17.31 feet, he said, all equipment on the south side of the existing bridge was evacuated.
As of this writing, the river level is down to 14.4 feet. When the level gets to 13.5 feet, crews can start putting equipment and materials back into place. “It’s going to need some power-washing,” Clayton Burke said; “and a little rain would be nice (to clean it up) - not too much, though!” When the river level is at 12 feet, the crews will be able to keep their barges in the middle of the river, and work can continue on Pier 2. “This is the work that will involve temporary (bridge) closings,” Clayton Burke said.
When that work resumes, intermittent closures of up to two hours will happen on the existing Black Hawk Bridge between the hours of 9 a.m. to 3 p.m. to reduce vibration from construction activity and traffic, limiting the chance of damage occurring. More information about the temporary closings will be made available by the Iowa DOT when the river level is low enough for work to continue.
WHAT WORKERS HAVE BEEN DOING
In an email interview following the bridge talk, Travis Konda, project manager with HNTB Corporation said that, in general, when a job is shut down and work is not available, the workers are either moved to another job if one is available or are laid off for the time being.
Office staff for both Kraemer and the Iowa DOT “have continued to advance the contractual work in a variety of ways, including but not limited to submittals, as-built documentation, and schedule review,” Konda said. “While work on the project site has stopped, the fabricators and suppliers are moving forward with building the steel truss, preparing the retaining wall panels, and planning for coming operations. Preparations are being made to resume work as soon as the river level allows.”
To read the full article, pick up the Wednesday, July 17, 2024 print edition of The Standard or subscribe to our e-edition or print edition by clicking here.
