The new Northwest Indiana bridge, more than 10 years in the making, resists flooding while serving as the centerpiece to the city’s lakefront redesign and beautification,
By Joe Frollo
Nothing beats a summer walk along a lake.
Cool breeze blowing. Birds swooping. Boaters floating by as families set up picnics.
It is an area that brings people together. It is for communities. It also benefits businesses that depend on foot traffic to thrive.
Designed and constructed correctly, a lakefront walkway can be the cornerstone in a city’s revitalization plan.
What Hobart, Ind., had before a new bridge went up over its Third Street thoroughfare was the opposite of that.
Wet, sloppy banks that too often flooded. Low clearance that cut boats off from a large section of Lake George. Crisscrossing utility wires overhead that added to the inaesthetics.
All of that changed thanks in large part to precast concrete allowing the new bridge to be more functional, thematic and picturesque as well.
“The mayor really wanted to tie the bridge in with the rest of the area’s development in order to bring everything together and create a showcase bridge that can be used and seen by thousands of people every day in the summer,” said Jake Dammarell, executive vice president with the Indianapolis engineering firm Butler, Fairman & Seufert. “With precast concrete serving as the base, it has a brick and limestone front. Another neat thing is the lighting and ornamental pieces that precast allowed us to construct, creating an atmosphere that ties into the streetscape and lights up the night.”
From single-span to four-span
The former 65-foot single-span bridge included just 44 inches of clearance, often leading to backup and flooding as water seeped into walkways and city streets. Replacing the bridge also meant addressing a water main and more than 12,000 paired copper wire utility lines that ran under the bridge deck.
Starting with a concept meeting in 2008 and culminating in the $7 million project that opened in October, the result is a four-span bridge with each span consisting of nine individual precast concrete arches that set from pier to pier and abut together, locked in place by keyways.
Pretek Group of Dayton, Ohio, designed the precast bridge under contract with County Materials of Maxwell, Ind., which manufactured the components, including wingwalls, headwalls and arch sections.
“For the wing walls, we put dove tail slots into them so they could use hand-laid brick to create the type of texture they wanted on the outside,” County Materials Technical Resource Engineer
Steve Smart said. “It was the same way with the head walls – precast inserts and galvanized steel apron bolted to the front so the brick ledge could be laid on top of that.”
With the utility lines not just converted and condensed to fiber optics but moved downstream, that cleared away any distractions for the added touch of LED lighting.
“The really neat thing is there are light boxes cast into the arch spans so they can actually illuminate under the bridge sections at night to give a nice, soft look,” Smart said.
A not-so-solid foundation
The biggest surprise arrived early on when soil tests showed – to put it mildly – a poor state.
“The soil in that area is complete garbage,” said Michael Eichenauer, executive vice president and bridge department manager at BF&S. “It made it a challenge to design the foundation. Usually, we’d have 30 feet for the piles at the foundation. We ended up going 70 feet because the soil was so bad for the first 30 to 40 feet that the geotechnical consultant said as soon as you stand those things up, they will sink 20 feet without even doing anything.”
Compared to that, the actual bridge design came together fairly quickly.
Engineers investigated multiple options. BF&S first considered box beams, but that didn’t provide the needed clearance. After that, engineers started looking closer at arches, and the city liked the look.
Plans were drawn up for a three-span bridge until the city decided it wanted to add a trail on the north end, which created the need for a fourth span.
The proximity of existing driveways and businesses prevented the adjacent road’s elevation from being raised. This created a challenging constraint. Another constraint was the water pipeline that the city would not move or bury under the river.
“We had some pretty tight clearances on that,” Eichenauer said. “It was really tight on the fill and pavement on top of these arches, and that’s about all we had.”
The arches worked and are only about a foot thick, Eichenauer said.
“When it was all said and done, the arch just looks more pristine, a lot better visual look,” he said. “The hard part with four spans is now we have multiple structures coming together and making sure everything fits on the foundation properly.”
Accommodating Traffic and Water
Each of the bridge’s four spans is comprised of nine individual 36-foot-by-9-foot arch sections positioned side by side. The arch sections range in width from 4 feet, 6 inches to 5 feet, 11 inches, which create the bridge’s 51-foot width. The four spans have out-to-out dimensions of just more than 38 feet, and the 9-foot interior arch height provides an additional 5 feet of clearance in comparison to the previous bridge to better handle water level fluctuations throughout the year.
The bridge accommodates one lane of traffic in each direction along with sidewalks. The bridge’s fourth span also serves as a walkway that runs underneath to the bridge’s travel lanes.
Smart said because of the soft earth and the length of the bridge, crews could only set half the bridge at a time before moving the 400-plus-ton crane to the other side of the lake. The crane stretched out about 150 feet at its maximum.
“You really have to maintain how you lay these things,” Smart said. “There were nine sections in each run, and they had to go 36 feet inside, 38 feet out to out. You set one side, maintain it, then get to the other end, and something could be two or three inches ahead of where it should be before you put everything together.
“The location also had a very tight working area. The sections were hauled on their sides and had to be unloaded and rotated in the air into the setting position. It was pretty elaborate the way they had to do it.”
County Materials also provided 24 headwalls.
The contractor, ICC of Elburn, Ill., favored using precast on this job.
“An advantage of precast is once we had the substructure complete, the precast was ready to go,” ICC Project Manager Tony Frazzini said. “We were able to schedule our trucks precisely and have them arrive on site as we set the precast in place. Precast really allows you to strategically plan work, coinciding with material deliveries, to expedite production and completion of the superstructure. Using precast made it much faster to complete this phase of the project.”
The wing walls are 20-40 feet long and segmented with holes for drainage pipes. They also are built to specific angles in order to meet and follow the road, which runs right up to the bridge and doesn’t leave much wiggle room.
In all, County Materials worked 10 months on the 18-month project, which included generating shop drawings, ordering steel and other materials, casting and curing the precast components, installation and inspections. The head walls were cast in 24 days, and the wing walls were cast in 12 days, while the 36 arch sections were cast in 36 days.
The final touch was applying a waterproofing membrane that lays overtop of the precast arch sections to ensure watertightness at the joints.
‘A centerpiece for downtown’
Hobart Mayor Bryan Snedecor called the new Third Street Bridge “the centerpiece for downtown” at its opening last fall. Along with flood mitigation and additional room for boaters, it also is historical as support logs from the previous bridge estimated at 100 years old were used as part of the decorations.
Work will continue along Lake George with this project serving as the template of what’s to come.
“The advantage of a precast bridge of this nature is an aesthetically beautiful structure,” Frazzini said. “The arches and wing walls allowed for the limestone façade and brick veneer installation, which provided just a magnificent final product. Everyone from the city and residents have given it nothing but compliments.”
Now, boaters do not just traverse the entire width of Lake George, but have a popular backdrop for selfies to remember their fun.
“Folks on the lake are thrilled,” Dammarell said. “We see a lot of social media posts with the bridge in the background. It’s become really popular.”
Joe Frollo is NPCA’s director of communications and public affairs and editor of Precast Inc. magazine.