Healdsburg's City Council is urging rail officials to allow an unused railroad bridge over the Russian River to be employed as a temporary bicycle and pedestrian crossing, but the possible resumption of freight train service may derail the proposal.

The City Council on Monday agreed to petition the North Coast Railroad Authority to authorize use of the bridge as a pedestrian and bike detour during next year's rehabilitation of the nearby Healdsburg Avenue bridge.

But Northwestern Pacific Railroad Co., which last year began operating cargo trains in Sonoma, Marin and Napa counties after a 10-year hiatus, is opposed, citing plans to resume freight service to Healdsburg next year.

"The wild card in this whole thing is whether the freight operator will allow this to go forward," Public Works Director Mike Kirn told the City Council.

Some council members expressed skepticism whether freights trains will begin running, given the repairs needed to the railroad bridge.

"When you see the condition of that bridge, it doesn't make a lot of sense," City Councilman Shaun McCaffery said.

But he acknowledged it likely will be "a tough time" trying to obtain use of the span for pedestrians and bicyclists when the Healdsburg Memorial Bridge is out of commission.

"I still feel this is very important. We need to explore every possibility until it's clear there's no alternative," Councilman Tom Chambers said before the meeting.

"The issue is one of access for both pedestrians and cyclists. It's our obligation to do everything we can to find a solution," he said.

The Sonoma-Marin Area Rail Transit Agency, which owns the tracks and the bridge south of Healdsburg, does not plan to run passenger trains across the river for several more years. City officials said SMART is receptive to allowing the bridge as an alternate pedestrian crossing.

But freight trains are a different story.

NWP Co. leases the railroad line from NCRA, the public agency that oversees freight service on the historic route.

Freight trains now run about twice a week as far north as Windsor. But NWP intends to make $1.3 million worth of rail and bridge repairs for five miles farther north to Healdsburg and to haul freight there by next December, NCRA Executive Director Mitch Stogner said in an interview. He did not attend the meeting.

A joint operating agreement "clearly gives the freight train operator the right to run freight trains," Stogner said. "As a practical matter, our board is not going to overrule the operator on this."

He said it does not seem feasible from a safety standpoint to allow pedestrians and trains on the bridge at the same time.

City officials are planning to close Memorial Bridge to all traffic, including cars, bicycles and pedestrians, for a major rehabilitation of the 91-year-old span that likely will get under way in July. Kirn said the bridge probably will be closed to all traffic around next November and will not reopen until January 2015.

Motorized vehicles will be able to use the Highway 101 bridge downstream as an alternate.

But for cyclists and pedestrians, closing the Memorial Bridge leaves them with no easy way to cross the river. The closest alternative is riding 10 miles out Westside Road to Wohler Bridge near Forestville.

Bike store owners, cyclists and members of the Sonoma County Bicycle Coalition have urged the City Council to find another crossing while the Memorial Bridge is closed.