A diversion pipe is being installed this week to route water being pumped into the Lake 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 at 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 temporarily permitted only 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 it will remain for about eight weeks.

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

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.

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. It also will be routed to keep the pipe in a shadier location during peak temperatures during the day.

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