Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Infrastructure topic
No spam. Unsubscribe anytime.
Geotechnical report finds Stevens Lake Dam unstable; consultant recommends breaching with sampling to guide remediation
Summary
Oasis Consulting reported that Stevens Lake Dam has high groundwater, weak soils and no confirmed keyway; the consultant said the embankment’s structural stability is 'marginal and should be remediated,' recommended breaching/re‑channeling similar to prior work at Marchman Lake, and estimated a preliminary breach cost around $750,000 and sediment sampling for contaminants before design.
Mike Montalione of Oasis Consulting Services told the board that geotechnical drilling at Stevens Lake shows high groundwater levels, no confirmed keyway/cutoff and poorly compacted soils inside the embankment. "Our study concludes ... the overall structural stability of the dam and the embankment is marginal and should be remediated," Montalione said, and recommended significant undercutting — effectively a controlled breach — and rechanneling to create a stable, self‑regulating swale.
Montalione likened the work to the earlier Marchman Lake breach, which the URA completed, and urged pre‑remediation sediment sampling to determine whether contaminants are present. He provided preliminary budget guidance: sediment grab sampling (field sampling line items were discussed with figures ranging from about $6,000 for a limited grab to $66,000 for more extensive sediment sampling) and a contractor estimate from Walden Ashworth of roughly $750,000 to breach and stabilize the dam, subject to detailed engineering and permitting.
Board members asked about potential downstream impacts, timing and liability. Counsel advised that while residents could pursue remedies in certain circumstances, ownership and legal responsibility depend on specific facts and that some sampling results might be handled under attorney‑client privilege during decision deliberations. Montalione emphasized the sampling is necessary before breaching because exposure of sediments could reveal unexpected contamination that would change the remediation approach.
Montalione also noted ongoing Army groundwater monitoring focused on PFOA/PFOS in the area and said the Army retains responsibility for groundwater monitoring that can be attributed to its historical activities. He requested permission to collect soil/sediment samples (including a specific request to sample at the old Forest Park firehouse to enroll that parcel in the Brownfields program) and asked the board to consider renewing environmental contract budget authority for 2026 to cover emergent needs.
Next steps recorded: the board authorized sampling work already budgeted (staff noted sampling had been approved previously but not yet completed) and agreed staff should confirm schedules and report back with sampling results and engineering/permitting proposals before committing to full breach design or construction.
