This article original appeared in Precast Today’s Q2 2023 edition.
By Shari Held
Regular communication and coordination were crucial at every step for a precast arch culvert bridge that stands as a key component of a California town’s master plan.
Located below the crest of the Sierra Nevada, just north of Lake Tahoe, lies the mountain town of Truckee. This site of the historic Donner Party tragedy is now a thriving cultural and outdoor sports center with a reputation as one of the best places to live in California.
An influx of new residents and tourists spurred the town to create the Truckee Railyard Mixed-Use Development Master Plan. The plan provides for new housing, restaurants, retail space, office space and entertainment venues along with new infrastructure to support it, including the Church Street Extension project. Due for completion in 2024, the project will connect the extended Church Street to a new roundabout on Glenshire Drive, linking the Railyard development to downtown Truckee.
At the heart of the project is a new precast arch culvert bridge crossing Trout Creek, which was realigned to allow it to flow into the Truckee River. The creek restoration will improve water quality, manage local runoff and provide 100-year floodplain protection for the town.
Ticking all the boxes
A precast arch culvert was the perfect choice for the new bridge, said Dan Wilkins, Public Works Director and Town Engineer for the Town of Truckee. Precast was preferred over cast-in-place concrete for the higher level of quality control that can be achieved during the production process and its speedy installation.
“Precast installations tend to go in much more quickly than cast-in-place where you have to do the formwork and rebar tying in the field,” Wilkins said.
An arch culvert design offered more advantages than other bridge types.
“They could have used three box culverts side by side,” said Jeff Von Handorf, P.E., a partner at Bellbrook, Ohio-based Pretek Group, the bridge designer. “But with the arch culvert, they could span the whole 32 feet without placing piers in the water. They didn’t have to disturb the stream bed during construction.”
Wilkins cited another advantage: “We were also looking for a structure that would have adequate clear span to create the hydraulic flow and floodplain area that was needed underneath the bridge but still allow us to have a natural bottom on the creek – as compared to a box culvert, for example.”
A buried arch culvert bridge easily accommodates variable widths of the road, sidewalks and berms lying on its surface.
“The town had some specific requirements as far as the roadway going across the structure, and the buried bridge allowed them to do what they needed with the road and meet all the geometry requirements of the road,” Von Handorf said.
Aesthetics was another consideration. The bridge will be visible from surrounding streets, and as the main entryway into the new Railyard development, it needs to be appealing.
The project’s proximity to Union Pacific Railroad property and Congressional Railroad right-of-way along with the restoration and redirection of Trout Creek required significant coordination with several entities to obtain special permits.
“The main challenge of the creek restoration and placement of the arch culvert was timing, to meet the environmental permitting requirements,” said Scott Mathot, P.E., senior engineer for the Town of Truckee. “Trout Creek needed to be diverted around the project area for the creek restoration to occur, which required significant coordination with the Lahontan RWQCB (Regional Water Quality Control Board) to approve the diversion plan and to meet the implementation timeline.”
Quick action also was important to ensure the precast bridge elements would be available as needed.
“The precast bridge was the first hurdle we encountered,” said Sam Duner, project engineer for general contractor Q&D Construction, headquartered in Sparks, Nev. “It was very important to get on Jensen’s production books early because they can get booked up quickly. The project required constant communication with them to make sure production was continual.”
One rather unusual, tricky challenge was that the slope of the head walls had to be an exact match to the existing grade.
“There was no room for error on this bridge,” Jensen Production Manager-Wetcast Abraham Ramirez said. “We had numerous meetings about it with Pretek to go over the plans and the form. There were so many components that had to line up just right when the precast pieces arrived at the field.”
Fabricating for perfection
Jensen Precast, headquartered in Reno, Nev., fabricated the precast components for the bridge – 14 arch culvert pieces, two headwalls and four wingwalls – at its Lockeford, Calif., plant. Each arch culvert piece measures 32 feet wide by 6 feet long by 10 feet high and weighs nearly 24 tons. The headwalls weigh more than five tons apiece and each wingwall weighs 10 tons.
A standard 5,000 psi concrete mix reinforced with prefab wire matting was used for the pieces. Each of the 14 span pieces were poured into a steel form and stripped via an overhead crane the following day. The wing walls were formed on a table, using 10- to 12-inch steel T-channel and poured separately.
To ensure a perfect lineup, the head walls were match-cast to the arch in the plant then disassembled prior to shipping.
The fabrication process took three weeks in June 2022. Each piece was inspected by Jensen’s QC technicians before shipment.
“The guys on the floor did a great job of making sure the job was poured right, and the rebar was installed according to the blueprints,” Ramirez said. “Everything went well, without any hiccups.”
Over a period of three days, a Mi-Jack crane loaded specific pieces onto flatbed trucks for the more than two-hour trek across the Sierra Nevada mountains.
One snag occurred related to the massive size of the elements. The trucks were prohibited from passing through the greater Sacramento area between the hours of 7 to 9 a.m.
“It was imperative that everything got loaded the day before and the trucks were on the road prior to 5 a.m. so we could set the bridge,” Duner said.
Mastering the logistics
Installation began the second week of July. Everything had to be precisely and proactively orchestrated.
The bridge hardware was delivered a week prior to the installation, lined up and ready for the precast pieces’ arrival.
“The precast bridge was one of the key pieces to the whole project since it will bring a lot of traffic into the new development,” Duner said.
“So, a lot of the planning centered around it. For example, the precast arch footings had to be dead on, so we had our foreman checking everything constantly.”
The bridge was installed east to west beginning with the headwall. Setting the elements went quickly – often the day’s quota was set by 12:30 p.m. – with the elements bolted together later that afternoon. Workers continued their way upstream until the arch was completed. The wingwalls were the last pieces to go in.
Q&D Construction installed the bridge in just three days. In retrospect, Duner figures it could probably have been completed in two days.
“Once the logistics were worked out, it was all smooth sailing,” Duner said.
Ramirez was also pleased with the results.
“It definitely was a challenge,” he said. “But we figured it out and made sure everybody involved was on the same page.”
Shari Held is an Indianapolis-based freelance writer who has covered the construction industry for more than 10 years.
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