Minnesota Zoo Treetop Trail
Apple Valley, Minn.
BEST PROJECT, CONSTRUCTION SPECIALTY
Sent by: PCL construction
General contractor: PCL construction
Main design company: Snow Kreilich Architects
Structural Engineer: Meyer Borgman Johnson
Civil Engineer: BARR Engineering
MEP: Food Engineering
Spanning more than 500 acres, the Minnesota Zoo at Apple Valley has large animal habitats, educational exhibits, and a meandering natural hardwood forest, along with a 1979 monorail that was decommissioned in 2013 and it served no one until it became a new attraction. , thanks to contractor PCL Construction, architect Snow Kreilich Architects and landscape architect TEN x TEN.
The $39 million investment to add the Minnesota Zoo Treetop Trail to the zoo was minimal considering it could use all of the old elevated train supports. SKA designed the world’s longest elevated pedestrian loop (1.25 miles) to convert the former train into a walkway above the zoo. Built on the old railroad track, the trail is at least 8 feet wide for its entire length, but has 22 exits that stretch up to 14 feet in places. The project adds 70,000 square meters of new space to the zoo that PCL built entirely to scale.
Photo by Corey Gaffer, Corey Gaffer Photography
PCL used a phased approach, dividing the path into four sequences to maximize efficiency. This approach took into account the daily routines of the zoo animals, the availability of supplies and the placement of cranes to avoid obstacles during construction.
What followed was a process that used the train rail itself as a material handling platform with a bogey wheeled tractor used to deliver the precast main sections at ground level, enabling an Easier location 32 feet in the air where the path leads to the zoo. .
“We designed it so that we could manufacture the entire system in 20-foot-long modules,” says Michael Osowski, PCL’s senior project manager. “That was all the framing and everything. It was fabricated, assembled, and then shipped to the job site in these 20-foot sections and then we were able to install the railing on the ground, and so it was completely safe .We got that section up on the track and then we were able to push it to its final resting place.”
Photo by Corey Gaffer, Corey Gaffer Photography
Osowski said that once the deck is on, then the electrical and lighting trades and other trades could do their jobs in a much safer way than if everything was built of poles.
The design of the existing on-track trolley system featured a subcompact diesel tractor with rubber wheels, a custom guidance system and a safety enclosure with access platform and canopy. The tractor wheels rode on the beam, driving the cart, while the guides made sure it stayed on track. The guidance system was based on hydraulic power, which allowed it to be lifted out of the way for ground driving and movement between access points.
It moved up to 30,000 pounds, pulled scaffolding, transported workers and pushed sections of trail to their final locations. For snow removal, during the winter months, PCL connected a 16-in. ATV shovels snow at the front of the cart, making the process more efficient and ensuring the trail remains accessible
Another uniquely Minnesota response to working through the record snowfall in 2022 was the use of ice fishing sheds placed on the wider section of the trail to provide warmth for up to four trade workers at a time.
“You could get an ice house, these pop-ups that are basically 18 feet wide that fit perfectly on the road, and then they were easy to move,” Osowski says.
