Passengers riding the new rail line between Sonoma and Marin counties may one day be able to spot a black-tailed deer or a night heron on wetlands owned by the Sonoma Marin Area Rail Transit system.

SMART has announced the purchase of 56 acres of wetlands along the Petaluma River that will be preserved as part of its environmental mitigation program.

The land straddling the Sonoma-Marin county line was bought for $2.55 million, SMART officials said. Pieces of the property will be restored as required to offset the project's environmental impacts.

Six to eight acres of the land initially will be restored to offset the loss of 2.2 acres of wetlands as a result of track construction between Petaluma and San Rafael, SMART general manager Farhad Mansourian said

"It makes a lot of economic sense and it's huge environmentally," he said. "Our passengers will have a beautiful site to look at."

The property, currently known as Mira Monte Marina just south of Redwood Landfill, is where San Antonio Creek meets the Petaluma River.

Environmentalists welcomed the purchase and noted that it will add to the 2,000-acre protected Petaluma Marsh system that supports an array of bird, plant and animal species, including the endangered salt marsh harvest mouse and California clapper rail.

"That marsh is so valuable," said Bill Kortum, founder of Sonoma County Conservation Action. "It's a big asset to Sonoma County."

The rail agency is required by regulators to offset environmental damage done during construction on the line by restoring a comparable wildlife area.

Agencies typically pay up to $1million per acre to a mitigation bank to restore wildlife areas that are usually outside the North Bay.

The purchase gives the agency an alternative to the mitigation banking system, Mansourian said. SMART can restore wetlands on the property as needed.

SMART officials said it is rare to find land for preservation within a project's area.

"This is a key piece of the Petaluma Watershed," said David Rabbitt, a SMART director and Sonoma County supervisor. "I am especially pleased by the size and quality of this single property, since opportunities for wetland mitigation are very scarce within the North Bay."

SMART commuter trains are expected to run between Santa Rosa and San Rafael starting in 2016. Trains eventually will run between Cloverdale and Larkspur.

You can reach Staff Writer Matt Brown at 521-5206 or