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Engineers tell Vernon County many PL-566 structures are hydraulically undersized and would require near-rebuilds to meet new rainfall data
Summary
Resource Conservationist Mark Erickson and NRCS engineer Steve Becker said many dams were designed with 1950s2D60s rainfall totals, have breached sections and cracking pipes, and would need extensive repairs or reconstruction under updated hydraulic standards.
Mark Erickson and NRCS State Conservation Engineer Steve Becker told the board that the dams27 original designs rely on older rainfall datasets and are hydraulically insufficient under modern standards. "The dams were designed with rainfall data from the 195027 and 196027s. The dams are not designed for the current rainfall amounts," Erickson said, adding that in many cases repairs would amount to building new structures because outlet pipes are too small and sandstone abutments allow seepage beneath embankments.
Erickson and Becker described specific engineering challenges: many pipes are cracked and leaking and would need replacement; stabilizing some sites will be difficult; and cutting a planned "V" notch to pass a 100-year event is intended to leave little residual embankment. Staff said stabilizing sites is the goal so the county can ultimately "walk away" from a restored site with minimal ongoing risk. Several dams have already been breached, demonstrating vulnerability to current storm regimes.
