Battling the Elements

May 8, 2000

Battling the Elements

Old Man Winter and Mother Nature bring about a new approach lighting system project

By Jordanna Smida, Assistant Editor

May 2000

LA CROSSE, WI — In 1999 the La Crosse Municipal Airport (LSE), located on an island in Lake Onalaska, underwent a four-month project to replace its approach lighting system. The lights, which extend out into the lake, had been pushed out of alignment by ice flows.

The approach lighting system for LSE's main runway, 18/36, extends out into the lake, which has made maintaining it an interesting challenge, says Mike Daigle, airport manager of LSE.

The original approach lighting system was installed during the ’70s. The lights located in the lake were on three small pilings that were about one foot in diameter, explains Mark Arnold, airport development engineer for the WisDOT Bureau of Aeronautics. "The forces of ice and wind had progressively pushed those towers and made them lean farther each year. It was getting more and more difficult each year to keep the lights in alignment," he says.

The leaning lights became a concern of safety for the airport's maintenance crew and for incoming traffic.

"The ladders to climb these towers were actually leaning over so you had to climb the ladder almost inverted or leaning backwards," Arnold states.

"Once the lights fell out of alignment, we had to turn them off," Daigle states. Not wanting to go without an approach lighting system, Daigle and his colleagues placed the system on its project list. The airport then hired Mead & Hunt, Inc., an engineering firm, to research the airport's options and oversee environmental work.

Determining ownership
True ownership of the lighting system became an issue with regards to funding for the project. According to Daigle, the airport and FAA couldn't decide who actually owned the lighting system. "During one of our early coordination meetings, someone from the FAA brought a finding that stated they were ours," Daigle explains. Daigle was satisfied with this decision, which meant the airport could apply for AIP funding.

Jon Faucher, project engineer with Mead & Hunt, says that coordination is fundamental when working with agencies like the Department of Natural Resources (DNR), Army Corp, U.S. Fish and Wildlife, and the FAA. Once the project received clearance from these groups, the airport was able to get discretionary funding for the project.

"We were fortunate to get discretionary funding to cover 90 percent of the costs," Arnold states. The state paid five percent and the city of LaCrosse also paid five percent of the costs. The total project with construction and engineering was just under $1.5 million.

A design to satisfy all
The new design had to minimize the effects on the hydrology, withstand ice flows, and factor in effects on the wildlife.

Because a majority of the lighting system was located in the lake, a number of environmental issues came into play. The Wisconsin DNR, which owns a 20-acre plot of land, including the shoreline where the lighting system is located, was concerned about the construction altering or changing the flow in the channel.

"The DNR and other agencies have done a lot of work in trying to make that area very good for fish habitat and they didn't want us to negatively impact the work," Arnold explains. Arnold says that a change in FAA regulations regarding the standards for approach lighting systems allowed the airport to reduce the number of towers that were in the lake from 13 to ten.

"We developed a structure where the main part was below the lake bed so we didn't affect or increase the cross-sectional area that was in the lake. Therefore, we didn't cause any possible flooding or damages," says Faucher.

The steel sheet piles, which support the structure, are driven 40 feet into the lake bed, Faucher explains. An 8 x 13 x 13-ft. cube of concrete was placed on top of it, which, according to Arnold, gives the structure its resistance. "A 36-in. diameter pipe was placed in the piling and filled up to three feet over the water level with concrete so the ice is pushing against the concrete instead of the hollow steel pipe," Faucher explains.

Aside of ice flows, "The difficulties were that it's a very soft, filthy lake bed. The structure had to be designed to withstand the weight of the structure itself," Faucher states. Another consideration the designers had to consider was the possible effects on the wildlife. "We had to make the structure big enough so a man could go on it and fix it, but small enough not to attract birds," Faucher states.

The new lighting structures also satisfied the safety issues that surrounded the previous ones. "The platforms provide a much safer environment for the technicians to work on the lights and the wiring," Arnold states. A 20-ft. frangible (breakaway) pole sits on top of the structure which holds the light, allowing the poles to be lowered to crews.

At the time of the lighting project, the state, Mead & Hunt, and the contractors were able to schedule the construction simultaneously with the reconstruction of runway 18/36. Traffic was rerouted to the airport's crosswind runway, 13/31, which according to Arnold, left incoming traffic without precision approach capabilities.

The construction process, Faucher says, involved bringing two concrete trucks out to the site on a barge. "At one time there were over eight barges out there, two had cranes and the rest were for storage," he explains.

Construction on the design also required some underwater work. Divers were needed to retrieve the existing structures, as well as remove the pieces used as guides in building the structures, Faucher says.

Most of the structures were placed near the same locations as the original system. "They weren't put in the exact same spots because when you are pulling those out you're disturbing the soil and we wanted to put these structures in existing compacted soil to increase the safety factor and stability," Faucher states.

CAPS A worker fills the sheet pile foundation with concrete The completed approach lighting system