Pownal stream study ID's flooding threats
A draft of the study report, prepared for Bennington County Regional Commission by consultants Fitzgerald Environmental Associates of Colchester, was presented during a recent special meeting of the town Select Board.
Company founder Evan Fitzgerald and Michael Batcher, of BCRC, said the 109-page document — called the River Corridor Plan for Tubbs Brook and Ladd Brook — will next undergo final revisions, following the Dec. 7 public information session.
Ultimately, they said, it will provide detailed information on sedimentation, erosion and other issues in the two streams and at the points where they drain into the Hoosic in Pownal.
That information can then be used by the town in seeking funding to reduce stream bank erosion, replace or remove outdated, undersized or plugged culverts, small dams, bridges or other structures, or to remove blockages related to trees, rocks or other natural debris in the brooks.
"We know flooding has been a concern in Pownal," Fitzgerald said during the presentation.
Batcher said the $30,000 grant-funded study, which was completed this year after an inspection of the entire length of the two brooks and their four tributaries in 2016, reflects an emphasis by the state on all aspects of stormwater management.
According to the report, Tubbs Brook watershed, which has origins in Bennington and flows into the Hoosic in North Pownal near the Petersburgh, N.Y., line, encompasses 5.81 square miles.
The watershed's highest point is at 2,300 feet above sea level, and the brook falls to 492 feet after crossing Route 346 to reach the river.
The Ladd Brook watershed falls from about 1,600 feet above sea level at Mason Hill near the Williamstown, Mass., line and encompasses 1.81 square miles.
Ladd Brook flows under Route 7 near the intersection with Ladd Road and then slants downward and to the south toward the Hoosic in the vicinity of the former Green Mountain Race Track and behind two mobile home parks, where flooding has occurred in the past.
The brook also flows under the Pan Am Railways tracks through culverts.
Fitzgerald told Pownal officials he had contacted railroad officials to learn whether Pan Am might consider upgrading the culvert site but learned that such a project "is not on their radar."
Field work for the project included measuring the width and depth of the stream channels, Fitzgerald told town officials, and examining streambank buffer zones, aquatic life and its ability to move past culverts or similar obstructions, and riverbank vegetation, all of which affects the concentration of sediment, erosion and can lead to flooding during storms.
Many of the 20 culverts examined were determined to be possibly inadequate to handle the volume with storm runoff, and some would not allow aquatic life to pass through.
Metal culverts in some cases are aging and likely should be replaced, Fitzgerald said.
"All of the culverts represented significant bankfull constrictions," the report states, "and 15 of the structures had widths less than 50 percent of bankfull. Twelve culverts do not allow for any aquatic organism passage and six of the remaining culverts have reduced [capacity for that purpose]."
Among the suggested remediation projects are work to replace culverts or bridges, remove small dams, such as might be put up to create a swimming hole; relocate a section of road or driveway away from a stream bank; add buffer zone plantings to better control stream overflow, and exclude cattle from areas around streams.
Pownal highway foreman Joel Burrington said this week that "there are a lot of projects on the list, but they will have to come up with the money."
He said that if the Select Board decides to pursue projects, he'll work with the BCRC to learn whether grant funding is available. The town is currently planning a culvert project on Skiparee Road for which funding has been approved, Burrington said.
"I think they will present us with the report, and we will have to decide how to proceed," said Select Board member Suzanne Caraman, one of the town officials who attended to presentation.
The study goals included establishing baseline information on the streams and the section of the Hoosic, including water flow, sediment buildup and erosion sites, and to prioritizing the potential remediation projects.
The entire draft report is posted on the BCRC website, at http://www.rpc.bennington.vt.us/
Jim Therrien writes for New England Newspapers in Southern Vermont and VTDigger.org. @BB_therrien on Twitter.
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