Commission asks for engineering calculations after 78 Main Street as-built differs from approved plan

The Southborough Conservation Commission asked the applicant for 78 Main Street to supply engineering calculations to verify compensatory storage after an as-built review showed the constructed compensatory area differs from the approved plan.

Commission peer reviewer Joe inspected the site and reported that while the garage and surrounding area appear stabilized, the compensatory-storage volume created on site (reported by the applicant as 50 cubic feet) is materially smaller than the 257 cubic feet that had been approved. Joe said the as-built topography and grading differ from the plans, and he recommended the applicant provide engineering calculations certifying that the as-built compensatory storage matches the permit requirement or otherwise correct the discrepancy.

Joe also identified other plan omissions: the final plan submitted to the commission lacked the required depiction of the compensatory-storage area on the grading plan (the “iceberg”/as-built), and a low retaining wall constructed near the garage is not shown on the recorded plan. While the created area currently appears to meet the minimum 1:1 storage ratio numerically, Joe warned the constructed grades and likely fill may mean the actual storage does not match the approved engineering.

After discussion, the commission confirmed it requires the engineering calculations and as-built plan revisions showing compensatory storage and the retaining wall location. The commission framed this as a required condition of the original permit and asked staff to relay Joe’s comments to the applicant and request revised materials and certification from the project engineer before issuing a final Certificate of Compliance.