Vague memories of the Mississippi

Thinking back on an odd event a couple decades ago... I rememberd that part of St. Anthony Falls dam collapsed and I was able to walk out into the Mississippi riverbed. The Internet came to the rescue and the foggy memory is now clear, thanks to FSTS Sources - Papers - ARCHAEOLOGY OF THE CENTRAL MINNEAPOLIS RIVERFRONT: PART 1 Archaeological Site Inventory - East Side Mill District: "The Lower Hydrostation formed the eastern end of the Lower Dam. The power potential was rated at 10,000 horsepower with a fall of about 20 feet. The powerhouse was built on a concrete base laid on the sandstone bedrock. Under the turbine roomwere 10 arched stone tailraces. The superstructure was built of a steel framework and masonry walls of salt-glazed tile. It contained one large room 250' x 50'. Most of the power was used by the Twin Cities Rapid Transit Company for streetcars. When NSP took over the plant in 1950, it removed the old turbines and generators and placed 10 new generators on the building's northern exterior directly above the headraces. The building interior was left essentially vacant.

"On November 9, 1987 the west end of the powerhouse was undercut by the river and the building partially collapsed. Most of the building was torn down in December of 1987 with the remaining part of the structure removed in late 1988."