Southborough commission approves orders for Willow Street culvert replacements with conditions after technical review

The Town of Southborough Conservation Commission voted to close hearings and issue Orders of Conditions for two culvert replacement projects on Willow Street, approving work for both the north and south crossings while adding several conditions designed to address hydraulics, monitoring and invasive species management.

Engineers from Parr Corporation and the town’s Department of Public Works presented the projects, saying one crossing (Willow Street North) has partially collapsed and that the other (Willow Street South) required plan clarifications. Bill Cundiff of the Town of Southborough DPW introduced the projects and Greg LaCroix, environmental scientist with Parr Corporation, summarized responses to earlier peer review comments from Lucas Environmental. "We provided proof in the way of plans to Melissa earlier today that the culverts have been in place since prior to 1983," LaCroix said, noting historical plans back to the 1950s for one crossing.

A focal point of the hearing was a technical exchange about the "openness ratio" used in Massachusetts stream‑crossing standards. LaCroix said the team’s calculation for one structure produced an openness ratio of 0.82 and that the plans meet state standards. "[The structure] has a life of 35 feet and a cross sectional area of 28.6 square feet, yielding an openness ratio of 0.82," LaCroix said. Eric Silva, the project manager, explained that a discrepancy between two plan sheets was caused by showing square corners on one sheet and a chamfer on the other; he agreed to update sheets so cross sections and elevations are consistent.

Joe of Lucas Environmental, who led peer review comments, agreed the clarification addressed his concern about the differing cross sections and recommended that the commission require elevations on cross sections to make the record clear.

Board staff recited proposed special conditions for the North crossing that the commission adopted: plants and root material removed from the replication area must be disposed of off‑site and not reused, a water control plan must be submitted and approved prior to site mobilization, a final PE‑stamped wall design must be provided prior to submittal for a 401 water quality certification, and the replication area must be monitored for two full growing seasons with an 80% success threshold for indigenous wetland plant cover before a certificate of compliance is issued. Staff also required invasive species monitoring and reporting with corrective actions if necessary.

Parr warned that additional external peer review could slow an urgent repair project for Willow North, which the team said needs expedited work because of roadway overtopping and embankment concerns. Silva told the commission the project team had already submitted hydraulic materials to DER as part of a CRMA grant review and offered to provide the town additional documentation if the commission requested it.

The commission voted by roll call to close the hearings and to issue Orders of Conditions for Willow Street North and Willow Street South with the stated special conditions and standard work requirements. The orders require Parr and the DPW to submit the specified plans and documentation before on‑the‑ground work proceeds and attach monitoring obligations to future certificates of compliance.

The commission’s conditions create a clear compliance path: engineers must correct plan sheet discrepancies, include cross‑section elevations, provide a water control plan and a final PE‑stamped wall design, and ensure post‑construction monitoring for the replication areas. The town staff will track required submittals before issuing permits or allowing mobilization for the culvert replacements.