HADLEY — Constructing an earthen berm along Bay Road to provide additional protection to the numerous properties located in the 100-year flood plain east of Middle Street is among ideas embedded in a report given to town officials following an in-depth study of the town’s levee system.
The Select Board recently received a geotechnical engineering survey from AMEC Massachusetts, Inc. of Chelmsford that recommends exploring an investment in building a new dike to supplement the 1.7 miles of earthen levee embankment along the Connecticut River north of West Street, and an additional 1.5 miles of the Norwottuck Rail Trail adjacent to Route 9, both of which act as flood protection for Hadley.
“A new flood protection system to the south may be a better investment and provide more overall protection to properties in town than improvements to the Rail Trail Berm,” the report states.
The levee, which starts from near the intersection of Rocky Hill Road and River Drive and runs toward the Calvin Coolidge Bridge, and the former rail bed that is now the Rail Trail, protects about 132 developed properties with 201 buildings on them.
Richard Niles, a project manager for AMEC who presented the findings at a recent board meeting, said the new dike might be a wise investment for the town, though that would have to be determined by the cost as compared to making significant improvements to what already exists.
“You would spend similar money and protect a lot more property,” Niles said.
The report, at a cost of $121,000, was based on 34 borings and taking core samples as part of a subsurface survey in the levee and flood protection system. This allowed an analysis of the stability, seepage and settlement of the dike and the Rail Trail Berm.
Originally built in 1928, the dike was damaged and extensively repaired following the Great Flood of 1936 and the Hurricane of 1938, and has been improved at times by the Army Corps of Engineers. In 2009, a crack was found in a section of the dike and, during repairs, a section collapsed and was rebuilt. That led to the complete evaluation that began in 2014 and the effort to be recertified to Federal Emergency Management Agency standards for a flood-prone area.
The engineers found that some portions of the embankments don’t meet FEMA’s requirements of slope stability and suggests ways to do so, including flattening or buttressing the slopes and improving soil strength properties. The report also recommends removing unwanted vegetation growth on or within the levee and Rail Trail Berm, which would create a better situation in case of a flood and would reduce the possibility of woody vegetation compromising the integrity of the dike through dead root penetrations, attracting burrowing wildlife or uprooted root balls in windstorms.
The report has additional recommendations that include: performing maintenance to prevent unwanted vegetative growth, poor sod cover, animal burrows and encroachments; completing a preliminary design evaluation to address the seepage and slope stability deficiencies; working with the state’s Department of Conservation and Recreation to reach an agreement to have the Rail Trail Berm maintained as a flood protection embankment; as well as having authorization to execute flood-fighting measures in the event of a flood.
Town Administrator David Nixon told the board that plans for the infrastructure can begin to be developed and incorporated into a capital plan for funding.
Select Board member David Fill II wondered if there was any possibility of having the dike certified to meet FEMA standards and then have the Army Corps take over responsibility.
That scenario is unlikely, Niles said, and noted there are not usually good sources of funding until a disaster happens.
In the past, Nixon said ensuring the town’s flood management system meets the certification requirements of FEMA would be beneficial to the town and homeowners to assess flood insurance costs and get possible federal assistance when flooding does occur.
Scott Merzbach can be reached at smerzbach@gazettenet.com.
