EAST ISLES — The Minneapolis City Council may take the owner of an Uptown luxury apartment building to court over what the city says is the illegal discharge of groundwater into the Chain of Lakes.
Pumps must move an estimated 170 gallons of groundwater per minute away from the foundation of 1800 Lake on Calhoun in order to keep the building’s two stories of underground parking dry. The constant flow through the storm sewer means city crews can’t access nearby sewer pipes for maintenance.
The 55-degree groundwater pours continuously from a storm sewer outlet into the lagoon between Lake Calhoun and Lake of the Isles. In the winter, thin ice and open water in the lagoon create a hazard for cross country skiers and others out on the lakes.
Lake and Knox LLC, a company whose partners include Uptown-based developers Nick Walton and Daniel Oberpriller, owns the five-story, 57-unit building with views of Lake Calhoun and a ground-floor restaurant. They proposed a solution in late September, but an Oct. 15 reply from the City Attorney’s Office instructed them to “go back to the drawing board.”
According to the city’s response, the Minnesota Department of Health would not accept a plan to dig wells and inject the groundwater back into the aquifer. There were also doubts that a “grout curtain” around the foundation could stanch the groundwater seeping into the basement.
Property manager Lynne Wyffels said they would continue to work with the city to find an acceptable solution.
The city granted a temporary dewatering permit in 2011 during construction of 1800 Lake on Calhoun, but the owners did not afterward seek another permit to continue the discharge. They would also require Department of Natural Resources permission to continue removing groundwater at the current rate, but the state agency rejected a permit application this spring and won’t issue a permit until an agreement is reached with the city.
Hired by the city to look into the issue, Barr Engineering in April reported the floor of the parking garage’s lowest level was between 18 inches and 14 feet below the local groundwater level, depending on seasonal fluctuations. It recommended a range of potential solutions, including abandoning a portion of the basement, relocating environmental and electrical systems and sealing it off.
The Minneapolis Park and Recreation Board planned to discuss legal strategies in the case in an Oct. 23 special session. Park Board officials have expressed concerns about the potential environmental impact of the groundwater entering the lagoon.
The city reports it will temporarily address the thin ice on the lagoon this winter by rerouting the storm sewer outflow to a “lesser-used area of Lake Calhoun.” It took a similar approach last winter, installing long, flexible tube that carried the storm water away from the lagoon to an area just off Lake Calhoun’s north shore.
That addressed the immediate safety concerns of City of Lakes Loppet organizers. Participants in the annual cross-country ski event cross the lagoon on the way to the finish line in Uptown.
The city was also seeking a way to clean a storm sewer grit chamber made inaccessible by the constant flow of water. A build-up of debris in the grit chamber, which requires regular cleaning and maintenance, could contribute to flooding in a heavy rain event, according to the Barr Engineering report.