The owner of an upscale apartment building in Uptown has found a novel — and expensive — solution to a lawsuit over a leaking underground parking garage.

Lake and Knox LLC, the owner of the 57-unit apartment at 1800 W. Lake St. in Minneapolis, wants to fill in the lowest level of an underground garage with sand and rock. The owners then want to build a tunnel to a new ramp on an adjoining piece of land and even provide 24-hour valet service until the new lot is complete.

The proposed agreement will also require the building owners to stop pumping groundwater from the parking garage into the Minneapolis Chain of Lakes, which sparked a lawsuit from the City of Minneapolis and the Park Board.

Under the agreement outlined Monday in Hennepin County District Court, the apartment owners must stop pumping groundwater by March 31. The building has been pumping 90 million gallons of groundwater a year to a nearby lagoon; that's enough to fill the seating area of Target Center.

"We're very pleased with this settlement," Park Board attorney Brian Rice said at the hearing.

The city of Minneapolis and the Park Board sued the building owners a year ago, arguing that the groundwater pumping was both illegal and harmed the quality of nearby waters, particularly Lake Calhoun and the lagoon between Calhoun and Lake of the Isles.

Judge Philip D. Bush ruled the pumping is illegal.

Rice is scheduled to discuss the litigation with the board in a closed session on Wednesday. The board is seeking damages to offset the impact of extra algae-feeding phosphorus that city and park experts say is carried by the pumped water into the lake.

The finer details of the agreement crafted by attorney Charles Nauen, representing the city, and Del Ehrich, for Lake and Knox, now will be fleshed out. The final deal is expected to be submitted to the City Council for approval in mid-January, and then submitted to Bush for formal approval.

"It appears this is a workable solution," Bush said after hearing the tentative agreement.

The deal calls for the building owner to reimburse the city $130,709 for extra sewer cleaning and to reroute the pumped water from the lagoon out onto Calhoun to minimize unsafe ice conditions for the City of Lakes Loppet ski races. It will also pay about $75,000 more for rerouting the flow in the coming winter.

Lake and Knox said in court filings that it plans to use valet parking temporarily and build a new underground ramp next door within a year to replace the parking it loses when it fills in its lower-level garage area, which was built below the water table.

Lake and Knox is now seeking damages from several of its technical consultants on the apartment project, which was completed in 2011.

The replacement parking is not part of the agreement, but Lake and Knox owners said replacing the lost spaces is crucial to hold on to tenants and ensure the owners have the cash flow to finance the work.

The owners plan to remove mechanical and electrical components from the lower parking level, fill it with sand and gravel, and then seal it off from remaining basement parking. The firm said that careful fill-in work is crucial to ensuring the building remains stable. It estimates the work will cost $1.2 million, while new parking is expected to cost $2 million.

"This is a big construction project, a lot of moving pieces. Everybody expects it will be implemented," Ehrich said.

"It is turning the basement into a much deeper footing for the building," Bush said.

The judge keeps jurisdiction over the deal in case disputes arise. The agreement allows for delays in the event of major weather challenges.

Steve Brandt • 612-673-4438

Twitter: @brandtstrib