Committee debates detention basin failures and whether contractor or groundwater is to blame

The committee spent a substantial portion of the meeting on the site detention basin that has not been reliably meeting the 72‑hour drawdown standard used in stormwater approvals. Consultants and committee members described evidence that the basin’s bottom became compacted contrary to specifications and that silt has clogged the planting soil layers; one committee member said puncturing the compacted layer with an ADS pipe allowed the basin to drain more quickly after rain events. A presenter said the contract drawings and specifications contained inconsistencies, with the drawings showing compaction while the specifications called for leaving the subgrade loose, and that the contractor’s subsequent compaction likely contributed to the problem.

The committee discussed remediation options and responsibility for costs. A consultant proposed a localized dry‑well or replacing the planting soil mix as options that might restore function without excavating the entire basin, but warned those options would not meet the 72‑hour requirement without a planning waiver. Committee members debated installing groundwater monitoring wells to obtain objective data versus removing and replacing the subgrade to meet the design; one member noted installing monitoring wells would cost “less than $10,000” and would produce useful evidence but would delay the schedule. The Chair said the formal direction remains to have Castania rebuild the basin to specification while decompacting material, and the committee requested the design team and legal counsel return with next steps and cost‑allocation recommendations.