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The Red Rock Hydroelectric Plant near Pella, Iowa, was commissioned late last year adding a new hydroelectric power-generating facility to an existing flood control dam that previously had no generation capacity. This six-year, $400-million retrofit the existing dam provides power for up 18,000 homes in the area. ENR Midwest reached out to Â鶹´«Ã½, the owner¡¯s engineer and designer-of-record, with some questions.

Rachael Bisnett, senior associate out of the Charlotte, NC office explained the penstock design ¡°The original concept included three concrete penstocks, which are large diameter water-conveyance conduits¡­ After review, the plan was revised to two larger penstocks, each centered within one of the concrete gravity dam monoliths. This change maximized the concrete cover relative to the monolith joints and reduced the width of the intake structure.¡±