Commission accepts Diamond Road culvert work designed for higher-capacity storms

Danbury engineers and the Environmental Impact Commission discussed a culvert replacement project for Diamond Road at the Aug. 26 meeting and accepted the draft determination of project impacts subject to Health Department conditions.

Tom Altermette, professional engineer, explained the drainage context: the project sits in a roughly 250‑acre watershed and replaces an older, frequently-clogged culvert with a wider, lower-profile structure. "This is a 250 acre watershed," Altermette said, and he added that the design uses a 12‑foot width and limited height to manage flow given channel constraints. Altermette said the replacement should reduce clogging and perform better for smaller, more frequent storms and be positioned to approach a 50‑year storm capacity as upstream and downstream channel improvements are implemented in the future.

Commissioners probed design storm selection, riprap and boulder protection, and the potential for higher velocities downstream. Altermette said riprap and boulders will be used at the sides and in the outlet area to dissipate energy. After discussion the commission moved to accept the draft determination subject to the six conditions listed in the Health Department letter dated 08/24/2026; the motion passed by voice vote.

Next steps: project moves forward with the listed Health Department conditions and with city maintenance expectations for the channel.