State and consulting engineers differed on Edenville spillway capacity and PMF; embankment stability later identified as critical
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Summary
Recorded depositions read into the Court of Claims record show consultants and EGLE engineers disagreed on whether Edenville’s spillway met the state's half‑PMF standard; engineers said gate tests, contraction losses and orifice flows reduced capacity estimates and embankment stability (liquefaction) was not fully assessed until post‑failure forensic work.
The Court of Claims on Jan. 27 received recorded deposition testimony from consulting dam engineers and state hydrologists that lay out technical disagreements over spillway capacity, flood modeling and embankment vulnerability at Edenville Dam.
Richard Perkypile, an engineer who prepared a January 4, 2019 memorandum assessing hydraulic adequacy, testified in a recorded deposition that his gate testing and technical memos found the dam hydraulically adequate under the then‑applied rules but that EGLE later raised concerns. Perkypile said gate tests in June 2019, and recalculation efforts afterward, included contraction losses and orifice flows that reduced effective spillway capacity. He also confirmed that the independent IFT/forensic review later indicated embankment vulnerability and concluded that buttressing or slope flattening would likely have prevented the embankment failure.
Perkypile testified he relied on the supporting technical information document (STID) materials available to him and that while he saw limited embankment‑stability issues (noting disturbed soils in one area), he had not conducted extensive geotechnical borings, laboratory strength testing or full embankment modeling. He confirmed that the embankment‑stability issue (including static liquefaction potential) became more prominent only after additional forensic review following the 2020 failure.
EGLE hydrologic specialist Susan Griner testified in her recorded deposition about how the agency calculates probable maximum precipitation and flood (HMR 52 and HEC‑HMS), and that EGLE used a representative PMF of about 63,000 cubic feet per second (CFS) and derived a half‑PMF of roughly 25,000 CFS for the watershed feeding Wixom/Edenville. Griner described checking Williams’ watershed delineations from a PDF (no GIS layers were provided) and identified sub‑basin area and runoff‑curve‑number differences; EGLE did not re‑run Williams’ HEC‑HMS simulations with EGLE’s alternative inputs, she said.
The deposition record captures the technical dispute EGLE and some engineers had with earlier contractor analyses: EGLE engineers, Spicer and internal reviewers identified reduced discharge capacity once gate limitations, contraction effects and orifice flows were included, producing lower capacity estimates than initial memos suggested. Perkypile and others also acknowledged that embankment‑level geotechnical work (borings and lab testing) was limited and that, according to later forensic reviewers, an embankment buttress could likely have prevented the left‑embankment failure.
The recorded testimony does not resolve scientific disputes — the court will assess these expert opinions, exhibits and follow‑up filings as part of the liability phase.