Uxbridge conservation commission continues Crown Shield Avenue stormwater review after applicant revises basin design

The Uxbridge Conservation Commission continued its review of the Crown Shield Avenue development on Sept. 2 after Oak Consulting Group presented revised plans that redesign the site’s stormwater management.

For the record, Sean Malone, a civil engineer with Oak Consulting Group, told the commission the project would subdivide three lots into five, with four units on most lots and a fifth lot holding the stormwater basin. Malone said eight test pits showed loamy sands and no pervasive groundwater, allowing the team to convert a previously proposed filter basin into an infiltration basin. "We have about 2 feet deep storage here. This is about 17,000 cubic feet of storage below the outlet, whereas our recharge requirement ... was in the neighborhood of 2,700," Malone said, describing a substantial increase in recharge volume.

Commissioners pressed the applicant on details. They asked for clearer phasing language and an agent inspection after Phase A but before Phase B to confirm stabilization and protect wetlands from sedimentation. Malone read the phase notes included in the plan, which call for constructing the basin and access drive first, establishing erosion control, installing utilities, and stabilizing disturbed areas before progressing.

The commission also discussed safety and maintenance. Malone said the basin’s maximum ponding depth is two feet and that, using a conservative infiltration rate of 1 inch per hour, ponding should draw down in about 24–30 hours. Commissioners raised the possibility that a pond could be an "attractive nuisance" for children and asked whether a fence should be required; Malone said the O&M plan assigns maintenance initially to the developer and then to the homeowners association, and that an estimated annual maintenance cost is about $3,000. Catch basins would be inspected twice yearly and cleaned at least once a year with additional cleaning if sediment accumulates.

Because the commission sought additional clarifications, including phasing references on plan pages, a documented inspection/approval step prior to Phase B, and consideration of a simple barrier or other safety measures around the basin, the panel voted unanimously to continue the Crown Shield Avenue Notice of Intent and stormwater permit to its Sept. 15 meeting.

Next steps: the applicant will incorporate commission comments, update plan phasing language and sequencing references, and circulate responses to Graves Engineering and the commission before the next hearing.