Dam demolition begins on Chicago River
by KEVIN GROSS
Demolition of the North Branch Dam at the joining of the North Branch of the Chicago River and the North Shore Channel began last week as part of a project to help increase fish migration and upstream accessibility for recreational activities such as kayaking.
Demolition of the 108-year-old dam, which has been known to many as "Chicago’s only waterfall," began Tuesday, July 31, at a ground breaking that featured representatives of the U.S. Army Corps of Engineers, the Metropolitan Water Reclamation District of Chicago, the Chicago Parks District and other officials.
Workers are also demolishing the concrete riverbank slopes behind the dam, which is located south of Foster Avenue and north of Argyle Street, to later build a series of riffles, steps pools, cobbles and gravel and sand, according to a press release. The step pools will have smaller drops between alternating shallow and deep water depths allowing fish and paddlers to travel upstream easier. Demolition work and creation of the pools should take about a year, according to officials.
The demolition and restoration project should cost about $4.5 million, with $2.7 million covered by federal funding and approximately $1.5 million covered by MWRD and park district contributions, according to Army Corps of Engineers and MWRD officials.
"Right now, fish and kayakers get to that location on the river, but they can’t scale the dam," MWRD public affairs officer Allison Fore said. "The work is going to make it much more friendly to the fish."
While the dam is located by nearby North Park University athletic fields and across from River Park, 5100 N. Francisco Ave., the impact of the project is expected to stretch much farther upstream as new fish species will populate previously inaccessible areas. Boaters and kayakers can paddle from the Chicago Loop to as far as Skokie, officials said.
"Eliminating the North Branch Dam is the natural next step in transforming the Chicago River system into a healthy, accessible resource," Friends of the Chicago River executive director Margaret Frisbie said in a statement. "Its removal will open up another 20 miles of the river for fish and make paddling safer."
"Due to water quality improvements, there is an increasing amount of biodiversity in and along our waterways and soaring recreation and economic investment along the riverfront," MWRD board president Mariyana Spyropoulos said in a statement. "All of this has sparked the upgrades that are currently being made."
Reclamation department biologists have seen an increase from 10 known species in Chicago-area waterways to 76 since 1974, which has resulted in a shift of ecological concerns, according to the release.
"When fish go upstream it allows animals like birds to feed and helps revive the whole food chain," Army Corps of Engineers Chicago District spokesman Patrick Bray said.
The dam was built in 1910, shortly after the North Shore Channel was created and the flow of the sewage-infested Chicago River was reversed away from Lake Michigan. Modifications were made to the overflow of the dam in the 1920s and the 1960s to speed up low flow and eliminate tree limbs and other debris that plugged holes in the dam, according to the release.
Bray said that as the North Branch Chicago River’s water level began lowering due to flow reversal and downstream engineering projects, the 4-foot-tall dam was intended largely to maintain the elevation grade of the North Branch River and slow water outflows, preventing sewage from flowing back north up the waterways or downstream erosion resulting from fast-flowing water.
"The problem with reversing the flow was the sewage didn’t all go south (to the Sanitary and Ship Canal), some sewage went north. That’s what the North Shore Channel was partly for," Bray said. "But when the North Shore Channel finished, you had an elevation difference between the North Branch River and the rest of the (waterway) system. The dam was built for that purpose, so that water didn’t just flow too quickly or just drain out.
"Over the past 100 years lots of improvements have been made as to how Chicago handles its sewage. There’s more tunnels, there’s the McCook Reservoir and there’s no need for a dam in River Park anymore," he said.
Additionally, a 2016 Army Corps of Engineers environmental assessment concluded that the dam’s secondary purpose of flood abatement was mostly obsolete, due in part to effects of the nearby Foster Avenue storm water diversion tunnel, which was recently completed.
"(The dam) has no effect on flood stages or attenuation," the report read. "Forces within the channel would be lessened by reducing the amount of water flowing through the confined channel."
As part of larger statewide efforts to rehabilitate local waterways, the dam is the second of four "obsolete" dams along the river’s North Branch slated for removal, including dams near the Evans Golf Course in Morton Grove and Tam O’Shanter Golf Course in Niles. The Winnetka Road Dam was demolished in 2015.
Additional environmental work, managed by Army Corps engineers and the Parks District and possibly taking up to five years, will result in the installation of various gravels, sands and natural vegetation along five acres of aquatic beds and 14 acres of riverbank, re-grading of riverbank land, invasive species removal and restoration of 29 acres of savannah habitat, both near the dam and near Ronan Park, 3000 W. Argyle St., and Legion Park, 3200 W. Hollywood Ave.