Tunnel and Reservoir Plan

History

19th century

The Deep Tunnel Project is the latest in a series of civil engineering projects dating back to 1834. Many of the problems experienced by the city of Chicago are directly related to its low level topography and the fact that the city is largely built upon marsh or wet prairie. This combined with a temperate wet climate and the human development of open land, leads to substantial water runoff. Lake Michigan was ineffective in carrying sewage away from the city, and in the event of a rainstorm, the water pumps that provided drinking water to Chicagoans became contaminated with sewage. Though no epidemics were caused by this system (see Chicago 1885 cholera epidemic myth), it soon became clear that the sewage system needed to be diverted to flow away from Lake Michigan in order to handle an increasing population's sanitation needs.

Between 1864 and 1867, under the leadership of Ellis S. Chesbrough, the city built the two-mile Chicago lake tunnel to a new water intake location farther from the shore. Crews began from the intake location and the shore, tunneling in two shifts a day. Clay and earth were drawn away by mule-drawn railcars. Masons lined the five-foot-diameter tunnel with two layers of brick. The lake and shore crews met in November 1866, less than seven inches out of alignment. A second tunnel was added in 1874.

In 1871, the deepening of the Illinois and Michigan Canal was completed to reverse the flow of the Chicago River to drain diluted sewage southwest away from Lake Michigan. However, the canal only had the capacity to drain to the Des Plaines River during dry weather; during heavy rains, the Des Plaines would flood and overflow into the canal, reversing its flow back into the lake. In 1900, to improve general health standards, the flow of the main branch of the Chicago River was permanently reversed with the construction of the Chicago Sanitary and Ship Canal. This further improved the sanitation of Lake Michigan and helped to prevent further waterborne epidemic scares.

20th century

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 and began to construct separate sewer and storm drainage lines. The primary benefit of wastestream separation is that storm water requires less treatment than sewage before being returned to the environment.

Flood damage grew markedly after 1938, when surrounding natural drainage areas were lost to development and human activity. Serious flooding has occurred in the Chicago metropolitan area in 1849, 1855, 1885, 1938, 1952, 1954, 1957, 1961, 1973, 1979, 1986, 1987, 1996, 2007, 2008, 2010, 2011, 2022, 2023 — but most record-setting crests occurred after 1948.

In the 1960s, the concept of Deep Tunnel was studied and recommended as a solution to continuing flooding issues.