Re: Downtown Minneapolis Riverfront - Mill Ruins Park - Waterworks
Posted: January 25th, 2017, 11:52 pm
Whoa. This needs to come true. Such an awesome reuse of the infrastructure.
Architecture, Development, and Infrastructure of the Twin Cities
May be true, but the Ford lock is maintained solely for recreational use. When the various invasive species get upstream anyway, what about opening the lock again for recreational purposes?acs wrote:Closing the lock was never about the carp anyways. It has everything to do with redeveloping the "blighted" industrial riverfront north of the locks. That much was made clear if you attended any of the "re-imagine the riverfront" workshops in winter 2015.
That's a weird place for scare quotes.acs wrote: the "blighted" industrial riverfront north of the locks.
So they created a tunnel under the falls, and that collapsed which expedited the erosion of the rest of the limestone cap of the falls. Water was leaking into the sandstone layer anyways above the falls and they would have eroded anyways in time, but this tunnel made things worse.Had explorer Hennepin arrived a few ticks of the geologic clock later, there would have been no falls for him to rename. Less than 1,000 feet upstream from the cataract, the limestone that capped the soft sandstone ended. Had the falls eroded this far, it would have disintegrated into a tumbling rapids. A scheme developed by William W. Eastman and John L. Merriam to expand milling above the falls nearly let slip the clock’s final seconds. Eastman and Merriam bought Nicollet Island, including its waterpower rights, in 1865 and then accused the millers of taking their water. To avoid a protracted legal battle, the millers compromised. They agreed to let Eastman and Merriam build a mill on Nicollet Island and run a tailrace to it from the toe of the falls. Excavation began on September 7, 1868, and by October 4, 1869, workers had tunneled beneath the limestone riverbed through 2,000 feet of sandstone from the edge of the falls and under Hennepin Island to Nicollet Island. That morning, workers discovered water leaking and then pouring into the tunnel’s upper end. The water quickly ate away the soft sandstone. Within hours, the 6-foot-square tunnel grew into a cavern 90 feet wide and 16.5 feet deep. The next morning, the overlying
limestone riverbed collapsed. A large whirlpool formed, sucking in everything nearby and spitting itout the tunnel.
Word spread quickly that the falls was disintegrating. Volunteers built a large raft and floated it over the whirlpool. They piled on dirt, rocks, and debris until it sank and plugged the hole, but another whirlpool appeared. Men built more rafts and sank them over the new break. By the afternoon, they inspected their work and celebrated “the triumph of human skill and brain over the dumb force of nature.” Nature took exception. As people scrambled off, the river devoured the feeble structures. One local newspaper exclaimed that the whirlpool tossed “immense logs and sticks of timber about as though they were mere whitlings,” standing them on end “as if in sport” and swallowing them.
Minneapolis residents and millers turned to the U.S. Army Corps of Engineers for help in stopping the falls from eroding. The Corps examined the falls in November 1869 but had no money and, with improved navigation its primary mission, no authority to help. Then, in July 1870, congress gave the Corps $50,000 to preserve the falls and save navigation above St. Anthony, which, local citizens argued, would become impossible if the falls collapsed entirely.
For three years the river baffled the Corps, as well as millers and citizens who tried repeatedly to plug holes and line the tunnel with concrete. But the water kept finding new ways under the limestone cap, scouring new tunnels and cavities, and the falls continued to erode.
A detailed survey finally showed that water was seeping under the upstream end of the limestone cap and eating its way through the sandstone. Unless blocked, water would undercut the remaining limestone, and the falls’ 12,000-year history would end.
Unable to save the falls by plugging leaks, the Corps in 1874 recommended building two low dams where the east- and west-side dams joined so that water would always flow over the central falls. The Corps also wanted to rebuild the timber apron started in 1866 to preserve the edge of the falls and, most importantly, construct a massive wall from one side of the river to the other under the limestone cap. Everyone agreed. In July 1874 the Corps began the wall that extended up to 39 feet below the 11-to-25 foot limestone cap. Above the limestone lay sand, muck, and the river. Despite quicksand, flooding, and continuing collapses, the 1,850-foot-long concrete wall was completed by November 1876. The great wall under the river secured the stability of St. Anthony Falls and, with it, the future of milling. (This wall is still in place, holding back the clock from its final tick.) The Corps next secured the rest of the falls, completing a new apron in 1880 that traded the natural vertical drop for a smooth, slanted slide across concrete. The engineers also built two low dams above the falls
to maintain a safe water level over the limestone at the falls’ center and constructed a sluiceway to carry logs over the falls. Finally, the Corps filled tunnels and cavities under the limestone with some 22,329 cubic yards of gravel. The sights and sounds of the natural falls disappeared forever.