New Hampshire landowners are fighting the Northern Pass project, a $1.1-billion transmission line designed to import a reliable source of renewable hydropower from Canada into New England, where transmission and generation are constrained.

Developers of the 180-mile line recently agreed to remove five alternatives for the line and focus on routes that would use existing rights-of-way south of Groveton, N.H., as well as a preferred route and several alternatives to the north that would require new rights-of-way.

In an April 12 filing with the U.S. Dept. of Energy, Northern Pass officials successfully obtained an extension until June 14 to identify a new route.

Martin Murray, Public Service of New Hampshire spokesman, says he is optimistic Northern Pass will be able to determine a route that gains local support.

Developers at Northeast Utilities, NStar and Hydro-Quebec say that some options— such as burying the line or putting it in the Connecticut River—are not feasible because of the prohibitive cost of using heavy equipment in remote locations.

The Northern Pass report notes that drilling or tunneling in the mountainous terrain—at depths typically ranging from 3 ft to 15 ft beneath the bed surface—may be necessary to obtain a flat and level line.

Maintenance of an underground line also would be challenging, the report notes. Diagnosis and repair might require extended outages. A partially underground option would pose problems because it would require transition stations at which overhead and underground portions of the line would have to connect.

Construction is scheduled to start in 2013. The utilities expect the line, which would bring 1,200 MW of hydropower from Quebec, to be in service by 2015.