A diversion pipe is being installed this week to route water being pumped into of the Calhoun-Isles lagoon, marking the second straight year that step has been taken to protect the lagoon's ice..

Minneapolis public works officials will contract for a 12-inch PVC pipe to be laid to divert water being pumped into the lagoon from an upscale apartment building t 1800 W. Lake St. The city recently sued the building's owner over the discharge of groundwater from the apartment site into a storm sewer entering the lagoon. The city argued that pumping was only temporarily permitted during the building's construction in 2011.

The diversion is an attempt to keep lagoon ice intact, according to Justin Long, an assistant parks superintendent. The Minneapolis Park and Recreation Board announced the diversion project on Wednesday but said the city is handling the contracting. It said the work will be completed by Jan. 16, and remain for about eight weeks.

The diversion project will cost about $45,000, according to the city, and extend for almost one-quarter mile.

Long said the diversion of water will follow a different route to Lake Calhoun this year. Last year, the pipe generally followed the east retaining wall of the lagoon before crossing near Lake Street to the north retaining wall of Calhoun, where it was discharged along the north shoreline. The plan this year is to route the pipe across the lagoon to its west retaining wall and follow that to the lake's north retaining wall. That will keep the pipe in a shadier spot during daily peak temperatures.

Last year, the pipe laid on the ice and the 55-degree temperature of the water it carried melted the pipe into the ice.  This year, the pipe will be raised a few inches atop spacers to prevent that, Long said. 

The main issue with warm water entering the lagoon is that softer ice endangers skaters and skiers, according to the city's lawsuit. It sued to end the discharge and to recover costs of dealing with the issue, including installing the winter piping.

Long said that park officials conferred with representatives of the City of Lake Loppet ski festival about how to include a ramp over the pipe for skiers for event races that use the lagoon and adjoining lakes.    

(Photo above: Chace Russell won a heat during ice-biking races held on the lagoon during the City of Lakes Loppet weekend.)