Sonoma County's proposed roundabout for Arnold Driver at Agua Caliente Road. Click to enlarge.

Sonoma County is proposing to build a roundabout on Arnold Drive at Agua Caliente Road, the entrance to the Hanna Boys Center, in the Sonoma Valley.

The roundabout, projected to cost $2 million if approved, would be built next spring and would be the first one on a major county-maintained road, officials said.

Rex Cummins, project design engineer with the county Department of Transportation and Public Works, said 2004’s voter-approved Measure M sales-tax hike specifically listed the intersection for some type of improvement. He said the intersection, now a four-way stop, has “a fair amount of delay” for traffic.

He said the county considered putting a traffic light at the intersection but went with the roundabout plan for environmental reasons. He said a stoplight would have required road work that, among other things, would have affected three nearby creeks.

Chris Seppeler, senior environmental specialist for the county’s Permit and Resource Management Department, said the intersection will be moved a bit west onto Hanna Boys Center property. He said the center was required to dedicate land for the improved intersection as part of county approval for a building project.

The proposal calls for putting native plants in the center of the roundabout, limiting cutting of trees to build the bigger intersection and replacing trees and shrubs that are removed.

The proposal will be discussed by the county Environmental Review Committee at 9 a.m. Tuesday in the public meeting room of the Permit and Resource Management Department’s office, 2550 Ventura Ave., Santa Rosa. Final approval is up to the county Board of Supervisors.

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