The Bedford Department of Public Works is asking Annual Town Meeting to authorize spending $950,000 to correct periodic flooding on and around Richard Road tied to a brook channeled into the neighborhood through culverts that are degraded.
The proposal, embedded in the capital article, is part of an effort to “address both immediate and longer-term issues related to stormwater and drainage through the municipal system of culverts, drains, and streams,” the warrant explanation says.
It references “a high failure rate of corrugated metal drain pipe that was installed in post-war subdivisions,” combined with “changing weather patterns that are creating the potential for more intense storm events as seen in this past summer.”
The floodwaters emanate from the sprawling White Cedar Swamp and contiguous wetlands north of Concord Road and on both sides of Davis Road. The primeval area is drained by the interestingly-named Mongo Brook, which is channeled through culverts under Concord Road toward Elm Brook a few hundred yards to the south.
There are three culverts between Concord Road and Richard Road, all installed in the 1950s, and they are corrugated metal that have reached their useful service life,” said Michael Sprague, engineer for the DPW. One has a diameter of two feet and the other two are one foot each.
About a year ago, he said, after some new flooding on Richard Road and Fern Way, “we found a lot of debris was blocking the culverts, and it became evident that they needed to be replaced or fixed,” Sprague reported. The DPW hired an expert to come up with some options.
“Because of age and deterioration, they are only able to pass eight cubic feet per second of flow,” Sprague explained. A so-called two-year storm, “which we have seen a lot,” produces about 20 feet per second, “so the culvert wasn’t able to handle what we typically see.”
The planned new design will accommodate flow from the so-called 200-year storm and match the capacity of the downstream culvert under the Reformatory Branch Trail, he said.
If Town Meeting approves the article – which will require a two-thirds threshold if bonded – the department will develop a schematic design and seek Conservation Commission approval, Sprague said, adding that there will also be contact with abutters.
The target to start construction will be late summer or early fall, “when water levels are typically at their lowest,” he said.
Sprague noted that for much of last year, a failing culvert resulted in a sinkhole on the eastbound side of Concord Road near the swamp.
“We fixed that with a treatment that essentially creates a brand-new pipe inside the existing pipe,” he said.
The capital article notes that “a culvert asset management plan is currently in development to help prioritize projects throughout town.”
Read more about the White Cedar Swamp here.
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