FARMINGTON — Selectmen posted a permanent vehicle weight limit on a portion of Whittier Road on Tuesday after approving an ordinance giving them authority.

The board imposed a vehicle weight limit of 23,000 pounds from a point one and a half miles south of the intersection with Seamon Road to Route 156. The limit takes effect immediately, but enforcement waits for signage. Signs were ordered Wednesday.

Trying to protect the road from riverbank erosion, the posting alleviates the vibrations of heavy vehicles until erosion along the banks of the Sandy River can be repaired.

Weight and vibrations contribute to the erosion problem, Town Manager Richard Davis said.

School buses and oil truck deliveries are exemptions to the posting because of necessity, he told Selectmen Ryan Morgan, Andrew Hufnagel and Jessica Berry.

Before the decision, the board held a public hearing and voted unanimously to adopt an ordinance restricting vehicle weight on posted ways.

The ordinance needs to be in place to back up the posting or “there’s no teeth in it,” Davis told the board. Without the ordinance, the board has no authority to permanently post any roads, he added.

Morgan said he had visited the erosion scene and had concerns.

“It’s a prudent step we have to take,” he said.

Whether RSU 9 will put school buses over the road is a judgment call for the school to make.

The start of the posting at 1.5 miles from Seamon Road will allow trucks passage to Kemp Enterprises, Davis said.

Another 10 feet of banking along the Sandy River has eroded since last fall, leaving just 40 feet to the pavement of the Whittier Road near the intersection with Route 156.

The road is monitored daily, public works director Dennis Castonguay said earlier this month. Heavy rains this spring and a tropical storm last summer have taken a toll on the river bank.

There is a plan for repair work but the town is waiting for word on a Federal Emergency Management Agency grant application for $235,000 and approval of the plan by the U.S. Department of Fish and Wildlife, Davis said.

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