EAST ISLES — The owners of an Uptown luxury apartment building may have to spend millions to resolve city and state concerns over groundwater being pumped into the city storm sewer system.
Keeping the two-story underground parking garage beneath 1800 Lake on Calhoun dry requires pumping more than 100 million gallons of groundwater a year into the storm sewer, according to a city letter to the Department of Natural Resources. The city granted the developers a temporary dewatering permit during construction of the building in 2011, but the city says the developer never requested a city permit to discharge water on an ongoing basis and was never granted permission to do so.
The 55-degree groundwater pours from a storm water outlet into the lagoon between Lake Calhoun and Lake of the Isles, and both the city and Park Board have raised concerns over hazardous thin-ice conditions during the winter and possible environmental impacts on the Chain of Lakes. The constant flow, estimated at 204 gallons per minute, also has prevented city crews from emptying a nearby grit chamber meant to capture solids flowing through the storm sewers, and it could contribute to flooding during heavy rain events, the city letter warns.
In addition to the city permit, the property owners require a DNR water appropriations permit to remove groundwater at volumes greater than 10,000 gallons per day or 1 million gallons per year. An application for a DNR permit was submitted earlier this year.
A 30-day review of the application ended May 9 with the department ruling that no permit would be issued until the property owners reach an agreement with the city, said DNR hydrologist John Gleason.
“We’re just basically holding off on a decision to let that process play out,” Gleason said. “We don’t want to do anything to interfere with the negotiation of a solution.”
The city hired Barr Engineering to look into the situation this spring, and in April the firm delivered a report outlining a number of potential solutions that ranged in scope and cost, from rerouting the water around the grit chamber ($100,000–$250,000) to creating a barrier to prevent groundwater from entering the basement ($6.6–$25 million). It did not present a cost estimate for simply shutting off the building’s two permanent dewatering pumps, which would require the property owners to seal off a portion of the basement and relocate the building’s electrical and environmental systems.
Barr estimated the floor of the lowest-level parking garage was 18 inches to nearly 14 feet below the groundwater elevation in the area, depending on seasonal fluctuations.
The property owners have hired a different firm, Braun Engineering, to prepare a second report on the situation, said property manager Lynne Wyffels.
“We are in the process of doing our own analysis and testing,” Wyffels said in early May.
Lisa Cerney of the Department of Public Works said she is in regular contact with the 1800 Lake property owners and, while they will be allowed time to study the situation and develop their own solutions, they hope to reach an agreement “as quickly as possible.”
Nick Walton and Daniel Oberpriller own the five-story, 57-unit apartment building through their company Lake and Knox, LLC. In its letter to the DNR, the city notes that the responsibility falls on the property owners to report and seek a permit for permanent dewatering.