One Southwest Crossing

Eden Prairie, MN

Putting a new precast addition on an old cast-in-place parking garage can be tricky. The existing ramp at One Southwest Crossing in Eden Prairie had two supported levels, but the last 60-ft bay stepped down to one level.

The challenge for Wells Concrete was to stack a new two-level, two-bay garage next to and on top of this old deck using precast beams, columns, double tees, and spandrels. The finished 200-space structure would visually extend the old deck with three levels of parking, including the open roof-top level.

The challenge, says Wells’ Gary Pooley, was to build on top of the old deck, which was only mildly reinforced, handle a complicated drainage situation, and match the decades-old color and finish of the existing garage. For the one-story vertical addition, the contractor did not want to put any additional load on the old structure.

Working with the engineer, Wells Concrete developed a plan to strategically cut holes in the existing deck slab and slide precast columns down to new footings. Since the ramp is built on a hillside with entrances at three levels, circulation ramps were not required.

The new deck aligns with the old so that you can drive directly from one to the other. But this created a drainage issue. The existing ramp drained to the south. The new ramp had to drain away from the structure to the east. This was accomplished by sloping the exterior spandrels up and down so that the new garage drains to these low points and out to a retention tank buried in the hill.

An even bigger challenge, says Pooley, was matching the rose and buff colors and finish of the existing garage. “We couldn’t locate the original precaster, so we had to start from scratch. We ended up trying two or three different rocks, two different sands, and numerous test samples.”

In addition, both a light sandblast and a heavy acid etch was needed to bring out the right color. Moreover, the spandrels have a white border, so Wells had to pay close attention not to stain the lighter border during the acid wash. “It took time to get it right,” adds Pooley, “but now it looks beautiful.”