You usually don’t see them. But the town is not neglecting its 119 culverts – not to mention several others beneath streets still labeled as private ways.
The Select Board on May 13 heard a report on the Bedford Department of Public Works’s culvert asset management plan, partially funded by a state Department of Environmental Protection grant. The asset management plan defines how to best maintain, repair, and replace culverts. The objectives are to inventory, assess, and prioritize the infrastructure.
Garrett Bergey, project manager with the town’s consultant on the plan, the firm Curran & Woodard, explained to the board that after field inspections, risk assessment and analysis, crews evaluated culverts for “likelihood of failure” and “consequences of failure.”
Each culvert was assigned a “likelihood-of-failure” score from one to five, based on physical condition. The average for the Bedford inventory was 2.84, which Bergey called “low to moderate.”
Four criteria were used to assess “consequences of failure,” Bergey said: health, safety, and property damage; traffic disruption; replacement cost; and impact on impervious surfaces. The average of 2.53 is considered high, but the score reflects potential, Bergey said. “But in general, if any of these do break, it’s not good,” he added.
By multiplying the likelihood of failure and consequences of failure indices, the consultants identified 15 culverts prioritized for repair or replacement. The single culvert requiring immediate attention is part of the fiscal 2024 capital plan and is “shovel-ready now,” said Michael Sprague, DPW engineer. Three more are in the “immediate action” category and eight are labeled “high priority.”
Bergey also discussed the town’s ongoing efforts to comply with federal stormwater drainage law through required “minimum control” measures: public education and involvement, detection and elimination of illicit discharge, control of stormwater runoff during and after construction at a specific site, and general “good housekeeping” and pollution prevention. Permit renewal is scheduled for this summer.
The town has more than 3,500 catch basins, more than 1,700 drainage manholes, and 327 storm drain outfalls connecting to 45 miles of stormwater drainage pipe, the report said.
Upcoming is a new round of field investigations, Bergey said, physically opening all the manholes in a drainage catchment and examining and sampling the flow.
“We’re looking for waste in the storm drain system,” he said.
He explained that particular offenders are “old homes entirely plumbed to the storm drain system,” or basement-level bathrooms installed without permitting. Leaking sewer pipes into groundwater can also be a source.
Bergey talked about particular efforts to remove phosphorus from the system because of that element’s negative impact on lakes and streams. An average of about 35 pounds per year is being removed, he reported.
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