By 1860, the city’s population had burgeoned to over 100,000, and the Chicago River had become a veritable cesspool as raw sewage and waste from the numerous slaughter houses and other industries flowed freely into it. With a significant number of its citizens dying from cholera and typhoid fever, the city hired Ellis Chesbrough in 1861 to serve as the Chief Engineer of the newly formed Board of Sewage Commissioners and tasked him with improving the city’s water supply and sanitary systems.
Chesbrough’s plan called for the excavation of a supply tunnel to connect a pumping station situated five miles inland to an intake crib located two miles out into Lake Michigan, well beyond the increasingly polluted shoreline. Dull & Gowan of Harrisburg, Pennsylvania signed a contract for the massive project on October 28, 1863, and work got underway the following May.
A wooden, double-walled crib, pentagonal in shape and with a height of forty feet, was built on shore and then towed into the lake by steam tugs and sunk in position by filling its hollow walls with stone. A cast-iron caisson was lowered inside the intake crib, appropriately named Two Mile Crib, and then driven into the lake floor. After the water was evacuated from the caisson, workers entered and excavated a vertical shaft to the prescribed depth before tunneling horizontally to meet the passageway being extended from shore.
Centered atop the crib was a rectangular building that contained a kitchen and bedrooms for the crib keepers along with storage space. Above this structure was a square tower that supported a birdcage lantern for displaying a light to warn mariners away from the manmade navigational hazard. The crib was also equipped with a fog bell that was struck once every minute during periods of poor visibility. Keepers lived on the crib year-round to tend the light and fog bell, and to operate the intake doors in the crib and keep ice from forming inside the crib.
As the population of Chicago continued to grow, additional cribs were built offshore. In 1898, the existing eight water intake cribs were capable of supplying the city with nearly a billion gallons of water each day. The cribs that exist today are Four Mile Crib (1891), 68th Street Crib (1892), Carter H. Harrison (1900), Edward F. Dunne Crib (1909), Wilson Avenue Crib (1918), and William E. Dever Crib (1935). The final crew of keepers was withdrawn from duty in 1990.
To thwart terrorist activity, security systems were installed on all the intake cribs in 2002. These systems include motion detectors, video cameras, and door sensors, and are linked to the Chicago Police through a microwave link. Vessels are prohibited from entering a buoyed zone around each crib.
Wilson Avenue Crib
Work on this circular crib, located roughly three miles offshore from the eastern end of the avenue for which it was named, began in 1915 with the sinking of a steel caisson having a diameter of ninety feet. Built using square-hewn granite blocks, the superstructure protects the inner well chamber that has a diameter of forty feet. An eight-mile-long tunnel connected the crib with the onshore pumping station.
On October 23, 1915, Wilson Avenue Intake Crib Light was established to mark the new crib during its construction. The fixed white light was suspended from a wooden post on a timber platform and had a focal plane of thirty-five feet. A fog bell was also installed to sound a single stroke every fifteen seconds.
When the crib was nearing completion, it was discovered that the superstructure was eighteen inches out of plumb. The concrete joining the superstructure to the steel caisson was blasted away, and three hundred jacks were used to level the superstructure. This delicate work delayed the completion of the crib until May 1, 1918.
A red circular tower topped by a lantern room was mounted atop the center of the crib’s roof to serve as a permanent navigational aid. This tower initially exhibited an acetylene light that was visible for up to eight miles. A fog bell, struck a double blow every twenty seconds, was used during low visibility.