Leave no trace

Star Tribune Tue, 22 Jan 2008 05:15:27 GMT
Southdale cooling system is uncool

The Edina mall's breakthrough pumps were "state of the art," but shifting environmental priorities are forcing a change. When Southdale opened in Edina in 1956, the nation's first enclosed shopping mall bragged that inside it was "perpetual spring." Stores and the giant interior court, with its towering bird cages and tropical plants, would be kept at a balmy 72 degrees by an innovative system that fended off "snow, soot [and] wilting heat." The heat-pump system that sucked cool water from underground was so innovative that it was featured in Business Week. Fifty years later, the same system still cools much of Southdale. But not for much longer. The shopping center is one of the last of 106 Minnesota businesses and other institutions that once used "pump-and-dump" systems, which pulled pristine water from an aquifer and dumped it into storm sewers and ponds after using it for heating and cooling. Once used by General Mills, Honeywell, colleges, government buildings and hospitals, the "once-through" systems fell out of favor after a 1988 drought. In 1989, state legislators passed a groundwater protection law that required pump-and-dump systems to be phased out. But the changeover has carried a high price tag, often running into the millions. And there are environmental trade-offs. While the new or reworked systems reduce the drain on the aquifer, they can actually use more energy than the old systems they replaced. Many of the businesses and institutions that relied on the systems have converted them to "closed-loop" systems that use water over and over again, cutting water consumption by 90 to 95 percent. Since the law passed, use of aquifer water by those systems has dropped from 11 billion gallons a year to less than 2 billion, according to the Department of Natural Resources (DNR).

[[keywords: LandUse;Living;Metro;]]