The Adirondack Park Agency approved Friday what it believes to be the less environmentally invasive option for extending an electrical line from St. Lawrence County to the tri-lakes region of Franklin and Essex counties.

The APA board voted 7-3 to allow National Grid to run the 46.5-kilovolt line along a 3.4-mile stretch of Route 56 in the town of Colton even though it cuts through almost two miles of forest preserve, which is protected from development. Staying near the highway will be less disruptive to forest and wetlands than hauling the line more than six miles around the protected area, the APA ruled.

Environmental protection groups have endorsed running the line through the preserve.

The New York Power Authority and National Grid are extending service from the Stark Reservoir, Colton, along routes 56 and 3 to Tupper Lake, Saranac Lake and Lake Placid. Those communities, which have municipal systems, have long complained of blackouts because of overuse and weather-related troubles on the National Grid framework delivering the electricity.

To allow construction through the preserve, National Grid and the state Department of Environmental Conservation have agreed to swap land. National Grid will give 10 acres on the Grasse River in the town of Clare to the state's forest preserve in exchange for six acres needed to construct the line along Route 56.

The exchange requires approval in a statewide referendum and from two sessions of the state Legislature. Lawmakers approved it in 2007 and are expected to vote in 2009. The referendum is expected to be on the November 2009 ballot.

NYPA and National Grid are building the line now and are targeting the end of the year for completion. They have an agreement with DEC that allows construction before approvals because it will increase safety for the tri-lakes region.

"We're going to work with our supporters until it passes," said Connie M. Cullen, NYPA spokeswoman.