Grand Coulee and highest dry falls cliff in the middle. It was created through the process of cataract recession, which included a cataract twice as high as its existing Dry Falls. Grand Coulee is two canyons, with an open basin in the middle. The Upper Coulee is filled, by Banks Lake, is long with walls tall. It links to the Columbia River at Grand Coulee Dam and leads southward, through the surrounding highlands. The entry to the coulee is above the Columbia. It began as the course of a Glacial Columbia River. The Wisconsin ice sheets Okanogan lobe extended southward across the
Grand Coulee Dam and during construction, workers and engineers experienced problems. Contracts for companies to construct the various parts of the dam were difficult to award as few companies were sizable enough to fill them. This forced companies to consolidate. In addition, Native American graves had to be relocated and temporary fish ladders had to be constructed. During construction additional problems included landslides and the need to protect newly poured concrete from freezing. Construction on the downstream Grand Coulee Bridge began in and more considerable earth-moving began in August. Excavation for the dam's foundation required the removal of of dirt and stone. To