WESTFIELD — The U.S. Department of Agriculture Natural Resources Conservation Service has published a draft watershed plan and environmental assessment for $7.7 million of work on Arm Brook Dam in Westfield. The federal agency is soliciting neighbors’ comments until June 23.
The proposed project will structurally rehabilitate Arm Brook Dam to meet the standards for a high hazard-potential dam and have a planned 100-year service life.
The city owns Arm Brook Dam, on Lockhouse Road, which was designed for construction in 1962. The Natural Resources Conservation Service evaluated the dam in 2019 to meet federal standards and will provide technical and financial assistance for the project.
City Engineer Allison McMordie acknowledged that it is a very long document, totaling 487 pages. She said readers looking for the essential highlights should see Section 2.0 for a summary and purpose, and Section 8.0 for the preferred construction plan.
“If they are interested in the environmental impacts, then Section 4.0 and 6.0 is the best spot for that,” McMordie said.
According to the plan, the total cost of the dam upgrade is estimated at $7.7 million.
Engineering and project administration of approximately $1.5 will be covered 100% by federal funds. The cost of construction will be split 65-35. Of the estimated total construction cost of $6.09 million, the city will contribute $2.1 million.
The city is also responsible for land easements and permits, currently estimated to cost $190,000. McMordie said this is a placeholder number — “We won’t know what’s required for that until we get the design.”
“According to Mayor McCabe, we will likely be funding this solely out of ARPA funds,” McMordie said, referring to the coronavirus pandemic-related aid provided to cities and towns by the federal government. “With the price increases that we’ve seen over the years, prices in general have gone up. This is also preliminary and final design hasn’t been completed, so the cost may shift some.”
She added that the $7.7 million figure “is just what they anticipate with what is required to rehab the dam — so any unforeseen issues won’t be accounted for. We will get a more accurate number as they dig into design.”
The preferred alternative design raises the top of the dam 6.5 feet through filling the dam crest and constructing dikes or floodwalls along the western side, construction of a labyrinth concrete spillway, replacing the low-level outlet gate and the embankment drainage system, and stabilizing the principal spillway riser.
The existing dam does not provide sufficient detention storage for a 70-year storm event, according to plans. The preferred alternative will rehabilitate to current standards for a 100-year storm event.
According to the report, the USDA agency and the state Department of Conservation and Recreation have categorized Arm Brook Dam as a high hazard-potential dam, based on the potential of loss of human life among residents, workers and motorists if the dam were to fail. In the path of floodwaters are 96 residences, 14 non-residential properties, 11 major roads including the Massachusetts Turnpike, one railroad, six bridge or culvert crossings and multiple utility lines.
During the city Flood Control Commission’s public hearing on the project Jan. 29, 2020, Jim Lyons and Deron Davis of the National Resources Conservation Service, and Allen Orsi and Matt Dean of Pare Corp., who had assessed the needs of Arm Brook Dam, summarized the process and spoke about the condition of the dam.
Lyons said the dam was built under the wetland protection and flood prevention program begun in 1954. In 2000, the president and U.S. Congress signed a law to work on upgrading the structures built in that period to current regulations. Arm Brook was selected for the project following a 2010 assessment.
He said Arm Brook Dam was built to protect Westfield against a 100-year flood, but the dam is now impounding more water than it was originally projected to handle.
”The dam is currently safe. We’re looking to upgrade it to current standards,” Lyons said at the 2020 hearing, adding, “Our purpose is long-term flood protection.”
“The dam is safe, in good shape, but it doesn’t meet current dam standards because rainfall data has increased,” Davis said.
The Natural Resources Conservation Service’s draft watershed plan and environmental assessment can be seen at bit.ly/rp17ns. A paper copy of the document is available for viewing in Room 311 of City Hall, 59 Court St., Westfield.
Comments on the draft plan may be submitted until June 23. Comments may be emailed to Deron Davis at email@example.com, submitted via phone to 413-253-4362, or mailed to: Natural Resources Conservation Service, Attn: Deron Davis, P.E., State Engineer, 451 West St., Amherst MA 01002-2934.
Individuals who require alternative means for communication should contact Deron Davis at 413-253-4362 or at firstname.lastname@example.org at least seven days prior to the end of the comment period.