The Ben Brook Bridge on Egypt Road in Alna needs repairs "as soon as practical" to avoid significant problems, according to the Department of Transportation.
The bill for repairs would fall to Alna, as the state classifies Ben Brook Bridge as a "minor span" on a town road.
An April 18 letter to the town of Alna from Assistant Bridge Maintenance Engineer Benjamin W. Foster details the issues with the bridge.
The downstream retaining wall shows "severe movement" with stones shifting away from the road. According to the letter, "if stones collapse into the brook, it could cause a serious washout of the roadway."
The letter follows a biannual state inspection of the bridge in July 2012.
The report recommends stabilizing the retaining wall and taking steps to divert surface water from the road.
"The bridge deficiencies should be addressed as soon as practical to ensure continued safe use of the bridge," Foster said in the letter. "Neglect of these deficiencies may result in a diminished function of the bridge through load posting or even closure."
The report shows the state has had concerns about the bridge since May 2006 and concerns about a serious washout since May 2010.
Alna First Selectman David Abbott said he and Road Commissioner Jeff Verney will look at the bridge and discuss a course of action at a future meeting of the Alna Board of Selectmen.
Ben Brook Bridge was built in 1955 and reconstructed in 1995, according to the inspection report. The bridge is 11 feet long by 24 feet wide and spans an 11-foot aluminum culvert.
Egypt Road runs northeast from Head Tide Road (Route 194) in Alna to South Clary Road (Route 215) in Jefferson.