Mall of America Runoff Endangering Refuge

For more than a decade, Pond C, a 4-acre storm water runoff collection area southeast of the Mall of America, has been a source of discord between Minnesota Valley National Wildlife Refuge (MVNWR) and city of Bloomington officials.After heavy rainfall events, the pond's problems become evident. A geyser of burbling water shoots into the air at one end of the pond--the result of thousands of gallons of storm water draining from the mall area on the bluffs above. Plastic bottles, alumnium cans, candy wrappers, fragments of plastic foam and other debris litter Pond C's banks.And less than 100 yards away lies Long Meadow Lake, a 1,000-acre spring-fed marsh that waterfowl and migrating birds call home. An overflow outlet from the pond releases water--in this case, polluted water--into the lake for drainage purposes.MVNWR leaders have long asked that less storm water enter the refuge area and that more be treated in holding ponds and other filtration systems, such as rain gardens atop the bluffs. Bloomington officials, on the other hand, said developers must meet storm water treatment requirements. Increasing the pond's size, despite its proximity to the refuge, is a solution to having Pond C perform its storm water treatment duties, they say.The Bloomington City Council decided to excavate and expand the pond in September. Mall of America Co. and Ikea will fund approximately half of the $1.8 million estimated cost. Digging is scheduled to begin in November, and work should be completed by June."It's our pond to maintain, and we're going ahead," said Jim Gates, deputy director of public works for Bloomington. "We have strived to maintain a good working relationship with the refuge, and it's been strained at times... The pond has been there for 25 years, and it should be a net benefit for the downstream discharge to Long Meadow Lake and the river. This will improve things."The pond has not been enlarged since its construction, primarily because of disagreement over how to treat storm water between the city and the refuge's previous manager. Relations have improved between the city and refuge since Patricia Martinkovic assumed the refuge manager position in 2005."I don't think we need to play the heavy, because... they have listened to our key concerns," she said. "Increasing the size of Pond C will definitely improve the quality of the water that goes into Long Meadow Lake."The city, which needs a special use permit from the U.S. Fish and Wildlife Service to access the pond from refuge land, will begin construction after the fall bird migration and suspend work during key migration periods in the spring, Martinkovic added. Replanting native vegetation will be another key part of the pond project.Refuge advocates, however, continue to express concerns about the 45-mile stretch of land. "The pond is in the floodplain, and if there is a flood event it could overwhelm the pond and whatever sediment and contaminants are there would become part of the river," said John Hickman, a board member for the Friends of the Minnesota Valley, a nonprofit group that helped establish the refuge in 1976. "The city and the mall have an opportunity here to demonstrate their commitment to effective storm water management by building storm water structures above the bluff and incorporating it into their development."Pond C is one of several storm collection ponds between the bluffs and river, but it handles a much greater volume of water than any other. Crews built it on Minnesota Department of Transportation land in 1979 expressly for the purpose of having contaminants settle out of storm water prior to its flow into Long Meadow Lake.The pond, however, has become too small to treat water draining from an estimated 2,300 acres of quickly developing land atop the bluffs. The area's increasing amount of buildings and parking lots means less rainwater can seep naturally into the ground.University of Minnesota representatives plan to study the effects of storm water on Long Meadow Lake this winter. Sediment, which can carry metals and other contaminants, thus robbing water of oxygen and inducing algae blooms, is the main concern. About 90 percent of sediment and 60 percent of phosphorous should be eliminated from water before it leaves a treatment pond, according to widely accepted standards.Water flowing from Pond C into the refuge has 64 percent sediment removal and 30 percent phosphorous removal, said Bloomington officials. Gates said the city believes roughly doubling the pond's size to 8 acres would remove 80 percent of sediment and roughly 55 percent of phosphorous; the expanded pond, he added, would "do a good job" of handling at least 2 in. of rain.Bloomington's Water Resources Senior Civil Engineer, Scott Anderson, said much of the development on the bluffs uses technology such as storm drains with grit chambers to separate solids and oil from parking lot water the flows to the pond. Ikea established a large rain garden when its store was built, and the city's Central Station development utilizes low-impact techniques to direct water into the ground rather than over the bluffs.Bloomington staffers pick up garbage from the pond area twice a year, and floatable-catching screens have had mixed success. While such efforts can help the situation, Gates said officials will never be able to rid the pond of all its pollutants.