FARMINGTON — An eroding riverbank that threatens a secondary road in Farmington is now at the point “where we start to have serious concerns,” according to one town official.

Local officials must decide whether the threat is great enough to close Whittier Road.

Federal and state agencies will have a telephone conference with the town on Thursday to help establish a timeline to stabilize the bank.

Since last August, when tropical storm Irene caused a major collapse of the bank of the Sandy River, the distance between the riverbank and Whittier Road has been shrinking.

Farmington’s municipal government has been sounding the alarm about the danger, but a $277,170 bank stabilization project is being delayed by the Federal Emergency Management Agency because of concerns about the impact on endangered Atlantic salmon.

Denis Castonguay, Farmington public works director, said the bank has lost two feet since early July, and now stands 31 feet from the road’s shoulder, and 35 feet from the pavement.

There is an additional four feet of overhang that is being steadily undercut, making the area extremely unstable, according to Castonguay.

“They’re just held up by the roots there,” he said. “A major failure, that’s our biggest concern.”

Pine trees on the bank have been cut down because of what Castonguay called the sail effect. When the wind blows, causing trees to rock in the ground, it speeds erosion in the riverbank below.

Castonguay said that, in discussions with Town Manager Richard Davis, a distance of 32 feet from the pavement could trigger a decision to close the road.

In that event, the town would ensure that residents on the road would still be able to access their homes. Only one driveway is in the affected area, and Castonguay said an alternative route to the home could be established.

In order to get approval for a bank stabilization project, the town must perform a biological assessment to measure the impact of the project on salmon populations. The Sandy River, a tributary of the Kennebec, is a key spawning ground for the salmon population in Merrymeeting Bay, which is at the mouth of the Kennebec. The salmon effort has been the focus of a multimillion dollar restoration effort.

The federal agency has pledged to support the town’s efforts to perform the biological assessment, and Castonguay said that it has identified companies that can perform the work quickly.

JoAnn Mooney, the state’s hazard mitigation officer, said one purpose of this week’s meeting is to try to clarify what other types of help the federal agency will give.

Castonguay said he didn’t know whether the agency would help to pay for the costs of the assessment.

Work on the bank needs to be completed by Sept. 30, the beginning of the salmon’s run, in order to be done this year.

Davis has said that the bank will collapse if the work can’t be done until next year.

Matt Hongoltz-Hetling — 861-9287

mhhetling@centralmaine.com