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Expert testifies Edenville Dam was hydraulically inadequate and unsafe before 2020 failure
Summary
William Sturtevant, a dam‑safety expert, testified the Edenville Dam lacked required spillway capacity (failed the half‑PMF standard), that regulators and owners had prior notice, and that keeping the reservoir at normal pool increased the risk of embankment failure.
William Sturtevant, a registered professional engineer and former state dam‑safety chief, told the court he concluded the Edenville Dam was hydraulically inadequate and unsafe before its May 2020 failure. "My opinion is they knew," Sturtevant said, referring to regulators and responsible engineers.
Sturtevant described reviewing decades of inspection reports, Federal Energy Regulatory Commission files and more recent consultant studies. He said earlier FERC and consultant reports repeatedly showed the dam could not meet the spillway capacity needed for its hazard classification, and that engineers in early 2020 (Luke Trumbull and others) calculated the reservoir would fail the half probable maximum flood (half‑PMF) standard.
The expert testified that when a dam cannot pass its design flood, holding the reservoir at its normal summertime elevation reduces available storage and makes it harder to discharge flood inflows. "By bringing this up to normal pool we reduce the amount of storage available, therefore reduce the hydraulic capacity even further," Sturtevant said, adding that lower, run‑of‑river operations would have reduced risk while repairs or spillway upgrades were completed.
Sturtevant pointed to site‑specific factors that, in his view, increased the hazard: historical construction with poorly compacted fills, loose granular soils found in borings on the failing (left) embankment, missing drains and the absence of a protective filter berm on that reach, and gate equipment that could not be lifted to its full design opening, causing restrictive orifice flow.
On methodology, Sturtevant said he used SEEDS (safety evaluation of existing dams), reviewed CSIR/12‑D reports, stability analyses and hydrologic/hydraulic studies, and inspected the documentary record of piezometer readings and soil borings. He told the court the combination of inadequate spillway capacity and embankment weaknesses made continued operation at normal pool significantly more dangerous than run‑of‑river.
Sturtevant also explained the difference between hydraulic adequacy (ability to pass design floods) and structural soundness (stability of concrete and earth components) and said the two are interdependent because design flood routing defines the loading used in stability analyses.
The expert’s testimony continued across multiple exhibits and reports admitted into evidence; cross‑examination was scheduled to resume remotely.
