Water crib
From Wikipedia, the free encyclopedia
Water cribs are offshore structures that collect water from close to the bottom of a lake to supply a pumping station onshore. The name crib is derived from the function of the structure—to surround and protect the intake shaft. Cities supplied with drinking water collected by water cribs include Chicago, Illinois, Cleveland, Ohio, and Buffalo, New York.
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[edit] Cribs in Chicago, Illinois
The City of Chicago is supplied with drinking water from Lake Michigan. The first crib, the Two-Mile Crib was constructed as part of a scheme by Ellis S. Chesbrough in 1865[1][2]. Water was collected and transported through a tunnel 60 feet below the lake surface to the Chicago Avenue pumping station[3]. This was replaced by the Carter H. Harrison crib in 1900 (located at ), which itself was intended to be replaced by the William E. Dever crib that was built alongside it in 1935[4]. However increased water demand meant that the Carter H. Harrison crib continued in service until 1997.
Other cribs include the Wilson Avenue crib (located at ), the Four Mile Crib (), and the 68th Street crib (). The tunnels leading from the cribs are close to 200 feet beneath the lake and vary in shape from circular to ovular and in diameter from 10 to 20 feet. Lake water enters the cribs and flows through these tunnels to pumps at the Jardine Water Purification Plant (the world's largest) and the South Water Purification Plant where the water is then treated. From there it is pumped to all parts of the city as well as 118 suburbs.
Until the 1990's, Crib Tenders lived on the cribs. Usually four man crews stayed aboard the cribs for a week at a time. Their duties included water testing, light maintenance, and dynamiting ice dams that formed against the cribs walls. Crib facilities included rudimentary bathrooms, showers, and bunk rooms – and a fantastic view of the city and lake.
The massive amount of polluted water that flows into the lake from Chicago is beginning to affect the water quality - even four miles off shore. The City of Chicago has proposed a plan involving the construction of new cribs twelve or fifteen miles farther north.
The Chicago cribs have also been designated a "security zone." In 2002 complete security systems were installed, including video, motion detectors, microwave link, and door sensors, all with direct links to Chicago Police monitoring stations. Any craft that enters the buoyed security zone is subject to boarding, ticketing and impounding.
[edit] Carter Harrison Crib Tunnel Collapse
In 1998 the tunnels leading from the Carter Harrison Crib to shore were de-watered for inspection, a process that was surrounded by controversy. Some experts feared that pumping the tunnels dry would result in a catastrophic collapse, while others guaranteed that collapse was not possible. The naysayers were proved right, and portions of the tunnel did in fact collapse. City lawyers soon filed suit against the engineers and contractors. The suit charged that the engineers, Alvord, Burdick & Howson, were negligent for advising the city that it was safe to drain the tunnels. It also charged that Luedtke Engineering Co., of Michigan, did the work in a way that caused the collapse. As a result of the collapse, the city spent $5.3 million to fill in a portion of the tunnel under Lake Shore Drive to prevent a possible additional collapse.
Carter-Harrison Crib Images
 Intake Pool, Carter-Harrison |
 Exterior View of connecting bridge, from Carter-Harrison to Dever |
 Interior view of kitchen, Carter-Harrison |
 Interior view of hallways, Carter-Harrison |
 Interior view of bunkroom, Carter-Harrison |
 Interior view of intake pool, Dever |
 Interior view of intake pool, Carter-Harrison |
 Exterior, from the West, Carter-Harrison and Dever |
[edit] References
- ^ Down The Drain: Raising Chicago. Chicago Public Library (URL accessed 14 October 2006).
- ^ Alice Maggio. The Lake Michigan Cribs Gapers Block, June 3, 2004.
- ^ The Lake Tunnel in Chicago. Linda Hall Library of Science, Engineering & Technology (URL accessed 14 October 2006).
- ^ Chicago Water Tower. The Chief Engineer (URL accessed 14 October 2006).
