The state Transportation Commission has approved $34.8 million to replace a Highway 101 bridge near the Petaluma River.

The construction work should begin this fall, said Suzanne Smith, executive director of the Sonoma County Transportation Commission.

The funds were approved on Wednesday and are the last of the money needed to replace the complex of four bridges over the Petaluma River and Highway 116 in southern Petaluma.

The work is part of the freeway widening project in Sonoma County and the Novato Narrows, which when finished will have cost about $950 million.

Two critical parts of the project, the Highway 101 overpass of Wilfred Avenue, $65.4 million, and widening of the freeway from Rohnert Park Expressway to Petaluma Boulevard North, $148.2 million, are expected to open this fall.

However, Sonoma County still needs $177 million to complete the widening through Petaluma and from Petaluma to the Marin County line.

Marin County also received $17.2 million to extend the northbound Highway 101 car-pool lane from Atherton Avenue to south of Redwood Landfill Road and $4.7 million to extend the Highway 101 southbound car-pool lane from Novato Creek to the Franklin/railroad overcrossing.

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