"The corps, an agency within the federal government, decided to build Olmsted with an experimental “in the wet” construction method: Hollow sections of the dam are built on the bank, skidded down to the river, towed into position and lowered into the water, where they are filled with concrete. Traditionally, a project like this would have used a coffer dam — a small temporary dam that keeps water out of the site while construction goes on in the dry.
The “in the wet” method was supposed to save time and money and minimize delays, but it did the opposite. By the time the corps realized its folly, it was too late to alter course. The novel construction process and inadequate congressional funding, among other things, have dragged the project past the quarter-century mark."