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On Southeast McLoughlin Boulevard, builders and designers are being challenged to transform an abandoned used car lot into a transit facility that looks like an urban forest.

The $13.1 million Southeast Park Avenue Park & Ride in unincorporated Oak Grove south of Milwaukie will resemble a natural habitat with a building dropped in the middle, TriMet project manager Jebediah Doran said.

Natural elements spawned from a lengthy design-build process with significant community input. They include 320 25-foot-tall, reed-like columns at the front of the building facing McLoughlin Boulevard as well as four “green screens” that provide a backdrop for a runnel system designed to channel stormwater into a large retention pond.

“The idea is moving from an urban (environment) to a natural environment, and allowing the building to be part of that transition,” Doran said.

The process is providing new challenges. Skanska USA Building encountered one excavating at the site, which had significant basalt rock common in the Oak Grove area, project manager Ryan Richards said. Skanska spent three months chipping out rock as it dug as deep as 15 feet to accommodate the garage.

The contractor then erected retaining walls on the building’s eastern side to allow a setback sufficient to let air move through all sides. That eliminated the need for a heating, ventilation and air conditioning system, Richards said.

“A lot of garages have exhaust fans,” he said. “This building doesn’t need it. It’s all open air.”

One tough task was setting 320 pipe sleeve columns tilted in different directions. On Skanska’s first attempt, grout would not hold the corrugated pipe footings in place, Richards said.

“The fact is that each one is its own animal,” he said. “It’s quite the detailing effort to get each one in its place.”

Skanska decided to use a rat slab base plate – a long concrete footing – below the actual footing so that it had something to work from. The fabrication shop, meanwhile, provided quality control.

“They were able to mount things at a specific angle, so when it comes out, it’s all set and the pipe is mounted to the base plate with the correct angle,” Richards said.

The precision required use of building information modeling, he said.

“You have to see these in three dimensions, to see how they turn and pitch,” he said. “Each one has to be turned away from the building. Each one turns either parallel to the building or perpendicular. It is random. I’ve never seen anything like this.”

For the runnel system, which takes about one-third of the water from the roof and channels it into a swale system, GBD Architects and PLACE STUDIO mocked up a design. It works essentially like a “mousetrap game,” said Paul Wroblewski, project manager for Portland-based PLACE STUDIO.

When water reaches the end of a channel, it spills over into the next. Perforations were cut into the channels to allow some water to drop straight into a stormwater swale at the bottom, for a cascading effect.

Designers identified channel angles allowing greatest efficiency for water to move through the system. They also had to measure perforation patterns so drops would not blow back into the garage, Wroblewski said.

“We want this to tumble over gracefully,” he said.

Photovoltaic panels and green roof elements also will help the three-level, 400-space parking garage achieve net-zero energy usage, Doran said. The building comprises only about 30 percent of the 2.5-acre property’s footprint; seven different habitats – including grassland, a riparian forest and an alder grove – are in the works.

“This whole area will provide the patch in a corridor of habitat linking the Willamette River and Kellogg Creek,” he said. “It will blend into the landscape’s ecology more than anything we’ve ever done.”

Southeast Park Avenue Park & Ride

Location: Oak Grove

Project cost: $13.1 million

Construction start date: January 2014

Anticipated completion date: November 2014

Owner: TriMet

Design-build contractor: Skanska USA

Architect: GBD Architects

Landscape architect: PLACE STUDIO LLC

Structural engineer: KPFF Consulting Engineers

Civil engineer: WHPacific