Environmental Engineering Reference
In-Depth Information
essary when old sources could no longer meet growing demand or became
severely polluted; questions of quantity
and
quality.The only viable alterna-
tives were abandoning older sources, then digging new wells; pumping
water from nearby lakes, rivers, and streams; seeking more distant sources;
and filtration (but not until the 1870s). Good location was a significant
advantage for cities forced to change or augment their water supplies. Fil-
tration (and treatment), however, eventually helped to defy the limits of
location, especially as the miasmatic theory was challenged by those who
found dangers in polluted water beyond smells and discoloration.
In some cases, cities took only modest precautions to ensure a good sup-
ply of water. St. Louis, for example, used the same system of pumping
muddy river water into a single 330,000-gallon reservoir until 1871. The
reservoir also served as a sedimentation basin. Pumping, with two rotary
pumps originally bought for use on fire engines, occurred only during day-
light hours, while the reservoir was used to supply demand at night.
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For Chicago, location offered new sources in close proximity to popula-
tion centers. When the town was founded in 1833, the water of the
Chicago River—a relatively sluggish stream with two branches which
divided the city—was considered pure, with some variation in quality from
season to season.Water also was drawn from shallow wells, since the site of
the town was only a few feet above the level of Lake Michigan. In the
1850s, especially as the Chicago River became more of an open sewer, the
public water supply was pumped from an inlet basin on Lake Michigan near
Chicago Avenue (a distance of 3,000 feet from the mouth of the Chicago
River). Lake Michigan offered a magnificent alternative as a water source,
extending over 22,400 square miles and with a watershed of 69,000 square
miles.
As the city grew (more than 100,000 people in 1860), and as the lake
water close to shore became increasingly polluted, the intake pipe was
moved further out and deeper into the lake. In 1863, the Common Coun-
cil approved a plan of the Board of Public Works to construct a two-mile
tunnel burrowed under the lake bottom connected to a new intake. This
first lake tunnel was completed in 1866 at an estimated cost of $600,000.
The project proved to be a much more difficult and complex engineering
task than anyone imagined. Duel and Gowan, the Harrisburg, Pennsylvania
engineering firm that won the contract, was faced with several problems in
tunneling below the lake bed. Most difficult was connecting the shore and
lake points on a straight line. Despite the arduousness of the task, this first
