Tunnel and Reservoir Plan
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The Tunnel and Reservoir Plan (abbreviated TARP and more commonly known as the Deep Tunnel Project or the Chicago Deep Tunnel) is one of the largest civil engineering projects ever undertaken in terms of scope, money and timeframe. The goal of the Deep Tunnel Project is to reduce flooding in the metropolitan Chicago area, and to reduce the harmful effects of flushing raw sewage into Lake Michigan by diverting storm and sewage water into temporary holding reservoirs. The project is managed by the Metropolitan Water Reclamation District of Greater Chicago.
The project was commissioned in the mid 1970s. Full completion of the system is not anticipated until 2019, but substantial portions of the system have already opened and are currently operational. Across 30 years of construction, over $3 billion has been spent on the project. [1]
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[edit] History
The Deep Tunnel Project is the latest in a series of civil engineering projects dating back to 1834 [2]. Much of the problems experienced by the city of Chicago are directly related to its topography. The city is largely built upon a historic marsh. The Chicago River was ineffective in carrying sewage away from the city; when it did, the earliest water pumps that provided drinking water to Chicagoans became clogged with sewage. These conditions led to frequent cholera epidemics in the 19th and early 20th centuries.
In 1871, the Illinois and Michigan Canal was built, diverting water from the Chicago River. In 1900, to improve general health standards, the flow of the main branch of the Chicago River was reversed to drain water from Lake Michigan, as opposed to having the river flow into Lake Michigan. This further improved the sanitation of Lake Michigan, and helped to prevent further cholera epidemics.
The construction of the Sanitary and Ship Canal (1892-1900), enlargements to the North Shore Channel (1907-1910), the construction of the Cal-Sag Channel (1911-1922) and the construction of locks at the mouth of the Chicago River (1933-1938) brought further improvements to the sanitary issues of the time. These projects blocked further amounts of sewage from draining into Lake Michigan. The projects also brought fresh lake water to inland waterways to further dilute sewage that was already in the waterways.
Surrounding farmland also engaged in flood control projects. The Illinois Farm Drainage Act of 1879 established drainage districts. These districts were generally named for the basin they drained — for example, the Fox River Drainage District. After World War II, suburban communities began to realize the benefits of separating stormwater from sewage water. The main benefit is that storm water needs less treatment than sewage before it is returned in to the environment. Communities after this time then began running separate sewer and storm drainage lines.
Flood damage grew markedly after 1948, when surrounding drainage area was lost to development and human activity. Serious flooding has occurred in the Chicago metropolitan area in the years 1849, 1855, 1885, 1938, 1952, 1954, 1957, 1961, 1973, 1979, 1986, 1987, and 1996 — but most record-setting crests have been set after 1948.
In the 1960s the concept of Deep Tunnel was studied and recommended as a solution to continuing flooding issues. The Deep Tunnel system would be built as a network of 109 miles (197 km) of tunnels of varying width.
[edit] Current status
2005 Update
As of October 2005, substantial drilling and blasting for the underground tunnels is complete. Reservoirs are slated to come online and be able to hold and process sewage in the future, notably in McCook (2013 and 2019) and Thornton (2014). Currently, water travels to the Thornton Transitional Reservoir, which will be abandoned in 2014. Water is also stored and held in the tunnels themselves while sewage treatment plants release treated water into the Calumet and Des Plaines Rivers.
2006 Update
Mining work is finished on the 7.9 mile Little Calumet Leg of the Deep Tunnel System, and final connections are scheduled for completion on March 1, 2006.
When the Little Calumet leg of the tunnel goes into operation, it will mark the total completion of all 109.4 miles of tunnel included under Phase I of the TARP project, and the culmination of 30 years of tunnel construction.
Stretching beneath Cook County, the tunnel is 15 feet in diameter, lined with concrete and is located at a depth of 150 to 300 feet below ground in limestone rock.
[edit] Impact
Impacts have been felt in both Lake Michigan and the Chicago River. Severe weather events as recent as the early 1990s have forced water management agencies to dump excess wastewater into the lake and river in order to prevent flooding. These incidents have been reduced as more of the Deep Tunnel system has gone online.
Long considered an open sewer, the Chicago River now hosts more than 50 species of fish and more wildlife along its shores. Riverfront property has begun to be classified more as an asset than a liability. Canoeing is once again allowed on the waterway, but swimming is still prohibited due to high pollution levels.
[edit] Notes
- In the mid 1990s, a heavy thunderstorm drenched the southern portion of the Deep Tunnel area with multiple inches of rain in short period of time. While the Deep Tunnel system performed satisfactorily by absorbing excess water, water within the system itself rushed north to the reservoirs at O'Hare International Airport and the Bahá'í Temple in Wilmette. Geysers of over 20 feet (6 meters) were reported in both locations for up to an hour as the water was redistributed more evenly through the system. A system of watertight bulkheads has since been installed to prevent the event from occurring again.
- During the Chicago Flood of 1992, the water from the Chicago River that leaked into the then-forgotten underground freight tunnel system was eventually drained into the Deep Tunnel network, which itself was still under construction.
[edit] Sources
- Horan, D. (2005). Deep Tunnel, Deep Ties. Chicago Tribune, March 14, 2005 via The Laborers Network. Retrieved December 23, 2005.
- American Underground Association's Featured Project. American Underground Construction Association, August 1999. Retrieved December 23, 2005.
- Deep Tunnel Project. City of South Holland Website. Retrieved December 23, 2005.
- Schmidt, E. (2004). Chicago's Tunnel, Reservoir Plan. McGraw-Hill Construction, August 2004. Retrieved December 23, 2005.
- Tunnel and Reservoir Plan (TARP). The Metropolitan Water Reclamation District of Greater Chicago, August 6, 1999. Retrieved December 23, 2005.
- Jones, S. and Waller, J. (2004). Chicago Public Library - Down the Drain. Chicago Public Library website, August 2004. Retrieved December 23, 2005.
[edit] References
- Sanders, S. (2005). WGN-TV CoverStories: Deep Tunnel. WGN-TV, October 10, 2005. Retrieved December 23, 2005.
- Juhl, Arland R. (2004). Flood Control and Drainage. Encyclopedia of Chicago. Retrieved December 23, 2005.
