Trees are being cleared and power poles assembled for a 115-kilovolt transmission line that is intended to improve service reliability and relieve capacity strains on high-demand days in the Anoka area.

Great River Energy, a wholesale power provider based in Maple Grove, is building the 5.8-mile line with several partners. Electricity demand in the northwest metro area “has strained the existing transmission system to its operational limits,” Great River says on its website. The line is scheduled to be working by July.

Only about 5 megawatts of unused power remain, about 10 percent of the capacity of the 69-kilovolt line serving Anoka, said company spokeswoman Lori Buffington. Five megawatts could be consumed by one large company moving into the Anoka area, she noted.

The project “will strengthen transmission line service and reliability and allow economic growth and development in the area,” Buffington said.

A major partner in the ­project is the Anoka Municipal Utility, which provides electricity to more than 13,500 residential and business customers in the city as well as in parts of Champlin, Dayton, Coon ­Rapids and Ramsey.

The century-plus-old ­utility is investing about $3.4 million to build a new substation, upgrade another and buy two new transformers. That is the largest investment the city has made in its electrical system, said Mayor Phil Rice and Dan Voss, Anoka’s electric utility director.

“This will provide [capacity] insurance,” Rice said.

Great River, the state’s second-largest electric supplier, will share the cost of the $11.7 million project with Anoka, Xcel Energy and the Minnesota Municipal Power Agency, a power company owned by 11 cities, including Anoka.

The new line, approved in August 2012 by the state Public Utilities Commission (PUC), will run from the Enterprise Business Park substation, near Hwy. 10 and the Anoka-Ramsey border, to Xcel’s substation at Main Street and Round Lake Boulevard in Coon Rapids.

Anoka Municipal Utility owns the Enterprise substation and will spend $691,000 to upgrade it for the new line. The utility also will spend nearly $1.2 million for two new transformers and about $1.5 million to build and buy land later this year for a new substation, Voss said. The facility will be located along the new power line near Garfield Street and 5th Avenue, a few blocks north of the Northstar Commuter Rail train ­station.

A number of hearings were held in the permit review process to obtain public and city comments on the proposed transmission line. A few Anoka residents objected to the line running near their homes, but city officials said the alternative route suggested by residents ran too close to the Northstar station and might interfere with the three-level station parking ramp and skyway over the tracks that are now in place.

The state Department of Natural Resources (DNR) testified at the hearings that Great River should take precautions to safeguard the Blanding’s turtle, a protected species found in the line area, and to protect birds and ­habitat on the Rum River — a state-designated Wild and Scenic waterway — which the line crosses beside the Bunker Lake Road Bridge.

The power line permit approved by the PUC requires Great River to follow DNR recommendations that include using wildlife-friendly erosion control matting, installing avian flight diverters and minimizing tree and vegetation clearing near the Rum and other public water crossings.