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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…
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