OTISFIELD — An engineer has suggested to selectmen that more culverts may be needed to prevent washouts on Cobb Hill Road.

Ross Cudlitz of Engineering Assistance & Design in Yarmouth informed selectmen that an initial observation of the road indicates “significantly more” cross culverts may be necessary to handle the flow from a larger watershed on Scribner Hill Road, which is above Cobb Hill Road.

Earlier this month, selectmen decided to ask Cudlitz, who also acts as district engineer for the Oxford County Soil and Water Conservation District, to survey the erosion problems on Cobb Hill Road to resolve drainage problems affecting the water quality of Thompson Lake.

A 2010 grant program through the Thompson Lake Environmental Association to help control erosion from sites, including Cobb Hill Road, into Thompson Lake was considered successful, preventing an estimated 52 tons of soil from entering the lake.

But major storms over the past year washed out Cobb Hill Road, despite installation of three culverts.

According to a letter from Cudlitz to selectmen dated Nov. 17, there appear to be numerous subwatersheds that combined could not be handled by the culverts. Cudlitz said a “very rough estimation” indicates there may be as many as 560 acres in the watershed above Cobb Hill Road.

Cudlitz said resolving the problem may take the placement of a culvert every 100 feet of ditch for the entire 12,000-foot-long road to handle a 6-inch rainstorm.

Selectman Rick Micklon said a landowner above Cobb Hill Road had cut some trees and left the debris on site. When heavy rains came, it may have washed that debris downhill onto Cobb Hill Road, plugging the culverts.

Cudlitz said with the amount of stormwater, there was little wonder that the culverts were plugged with debris.

The board has asked Cudlitz to work with Otisfield Conservation Commission Chairman Jeff Stern of Fiddlehead Environmental Consulting and Road Commissioner Richard Bean on the project.

Micklon said Cudlitz inspected the original Cobb Hill Road culvert project but did not do the engineering.

“We thought since he was last on the scene we would turn back to him to give us a better perspective,” Micklon said.

ldixon@sunjournal