When Richfield decided to build a new public works maintenance facility, it wanted it to make it as green as possible.

Though the machines inside might be oily and spattered with salt, the City Council reasoned, there was no reason the building and its site couldn't be a model of environmental sensitivity.

Now, the $12.9 million public works garage is set to open later this month. And what looks ordinary from the outside -- a gray 98,000-square-foot industrial-style building with garage doors -- isn't ordinary at all.

Nearly surrounded by water-collecting rain gardens, the site features a parking lot with permeable paving that should allow rain to seep into the ground as easily as if it were sand. Eighty hidden 200-foot-deep wells use the constant 50-degree temperature of the Earth to moderate water temperature in a closed system that will heat and cool 40 percent of the building. Massive skylights over the main vehicle storage area will light the area on all but the darkest days.

In the second-floor administrative area, sensors will turn lights on when someone enters an office and turn them off if there's no activity for 8 minutes. An energy recovery unit will save heat from air that leaves the second floor. Desk partitions were bought used from a furniture dealer.

The carpet was made by a company that uses a zero-waste manufacturing process. When the carpet needs to be replaced, the company will take it back and reuse it. Even the paint on walls inside the building was selected for its environmental friendliness.

The building should be 30 to 35 percent more efficient than a structure built to standard construction codes, said architect Nancy Schultz of Short Elliott Hendrickson Inc. in Minneapolis. It was built on just four acres at the southeast corner of W. 66th Street and Hwy. 77, adjacent to runways at Minneapolis-St. Paul International Airport.

"The big challenge here was lack of area," Schultz said. "We compacted the footprint to make a more eco-friendly design."

To make room for rain gardens and a holding pond that will handle drainage on the site, which is hemmed in by roads, designers gave the building a big basement. A giant elevator as big as a good-sized room will carry city lawn mowers, manhole covers, light poles and even pickups to the lower level for storage. Larger equipment like snowplows will be stored on the main floor, which has a bay for washing vehicles and a repair space with a giant crane for work on big machines.

In the roughly 10,000-square-foot parking lot, the city is installing both pervious concrete and asphalt to test durability and effectiveness. The hard surfaces, which will look something like the top of a Rice Krispies bar, will be laid about 9 inches thick on top of 2 to 3 inches of washed 1-inch river rock with about 3 feet of 3-inch stones underneath. Salt can't be used on pervious pavers, but water should pass so quickly through the paving that it doesn't have a chance to freeze. To keep the parking lots free-draining, the city will have to sweep the surface to prevent pores from being clogged with sand or other particles.

Schultz said city officials wanted to use the permeable paving partly to demonstrate to businesses that it can be done. "They felt that if they're asking people to do it, the city should do it," she said.

While the landscaping necessary to keep water on the site appears costly, Schultz said the paving and the pipe-and-drain system that directs excess water from rain gardens to a retention pond are no more expensive than installing new storm sewers. They are likely to be prettier, too, with native plants planted along the sloping sides of the rain gardens.

The Richfield City Council decided not to seek certification that would proclaim the building's environmentally friendly design, choosing instead to spend the tens of thousands of dollars such certification costs on the building itself.

The new building is a big step up for the city's public works department. The department's main building was literally cut in half years ago when W. 77th St. was extended through the site. Equipment and vehicles are stored not only there but on a park field, in a former mortuary owned by the city and at other locations.

All those scattered public works activities -- water, sewer, forestry, building maintenance, streets, parks and utility billing -- will be based in the new building. Randy Hughes, public works' operations superintendent, said the department does a lot of cross-training of employees and it will be much easier to have everyone in one place.

He is so enamored with the building that he jokes he might have to push his retirement, still a few years away, even further back.

"I love it," he said. "It's going to be great."

Mary Jane Smetanka • 612-673-7380