HEALDSBURG BRIDGE WORK MAY START IN SUMMER:SEISMIC, 'SCOUR' RETROFIT EXPECTED TO TAKE 3-4 MONTHS,WITH LITTLE INITIAL DISRUPTION

Work likely will begin this summer on Healdsburg's historic Russian River bridge to help it withstand earthquakes and erosion.

The seismic and "scour" retrofit will take three to four months, but the 90-year-old bridge will be closed to traffic only for about a week of that time, a consultant told the City Council Tuesday.

The city is hoping to obtain the necessary approvals from Caltrans next month, followed by federal and state funding for the $2.7 million job. A second, $4.7 million phase of bridge rehabilitation is scheduled for next year, but it will have greater traffic implications. Vehicles will be kept off the span during the entire 4- to 6-month project.

Council members said they were pleased with the progress on the iconic crossing, known both as the Healdsburg Avenue Bridge and the Healdsburg Memorial Bridge.

The fate of the 1921 bridge -- whether to rehabilitate it or build a new one -- was debated off and on over the past several decades in Healdsburg. The vintage, steel-truss structure carried the old Redwood Highway over the Russian River, but was eventually supplanted by a new Highway 101 bridge to the west.

The old bridge's narrowness and questions about its earthquake and flood safety made its future uncertain, especially in light of a 1979 Caltrans report that gave it a failing grade.

But several years ago, the ratings used by Caltrans were found to be in error. After they were revised, state engineers acknowledged the bridge is capable of carrying all legal loads. But there are still width, height and size limitations that led to pressure for building a modern new bridge.

In September, the City Council, bowing to preservationists and prevailing public opinion, decided to save the old structure. The council made rehabilitation the "preferred alternative" for an ongoing environmental study of the bridge.

On Tuesday, the council was informed the seismic and flood resistance work will consist of drilling 7-foot-iameter, steel-casing pilings deep into the river bed, next to the central foundation. It will make the support pier appear slightly wider and longer.

The second phase of work, in 2012, will concentrate on the upper part of the bridge. It will include deck replacement, re-painting and repair of damaged members and railings.

Mel Amato, a Healdsburg electrical engineer who discovered the Caltrans calculation errors, told the council "it looks like the project is headed in the right direction."

He said he was a little concerned that traffic volume predictions -- vehicles trips will increase by 50 percent in 25 years -- were unrealistic and could make engineers think the bridge will be "overstressed and overused."

You can reach Staff Writer Clark Mason at 521-5214 or clark.

mason@pressdemocrat.com.