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Ask Chicagoist: Lake Michigan Structures?

By Thales Exoo in Miscellaneous on Mar 16, 2007 2:44PM

Dear Chicagoist,

When you look out on the lake (east, obviously), way out, there are structures of some sort. What are they? Do people work there?


2007_03_askcribs.jpgThanks for writing, Laura.

We think what you're seeing out there on the lake are structures that are called water cribs. Water cribs are an integral part of Chicago's water filtration system, which as you may know, is based around Lake Michigan — that's where we get our drinking water. That's not something that always sounds too appealing, but it seems to have served us fairly well, and when it doesn't, well, we just change the direction of the water flow.

Water cribs "collect water from close to the bottom of a lake to supply a pumping station onshore." They're called "cribs" not because they're swank MTV-style homes, but rather because, like a baby's crib, they surround and protect the intake shaft from any outside pollution or contamination. The water is collected and then transported via pipes 200 feet below the lake's surface to pumping stations (like the Chicago Avenue pumping station) at purification plants at the shores of the lake, and from there the water continues on its fabulous journey which ends when you fill up your Brita pitcher at your kitchen sink.

But back to the cribs. The first one, the Two-Mile Crib, was built in 1865 (and was predictably located two miles offshore) after a recommendation by Chicago Board of Works' engineer Ellis Sylvester Chesbrough. Chesbrough thought building the crib would help with the water pollution problems Chicago was facing at the time. By putting the crib in an area with low pollution and digging tunnels to transport the water, they were able to avoid areas of high pollution; in fact, they wound up moving the intake point multiple times as pollution increased. The original crib was made of timber, and the original tunnels were lined with brick.

In 1900, the original crib was replaced by the Carter H. Harrison Crib, and then eventually Chicago's water needs required more than one and the William E. Dever Crib was added in 1935. Now, there are multiple cribs scattered along the lakefront from Wilson Avenue to 68th Street.

No, no one works on the cribs anymore. The cribs used to have crib tenders working and living on them, performing water testing and general maintenance duties to keep up the operation of the crib. Think lighthouse keepers without the big lights. Workers lived on the crib for one-week shifts — something of a bizarrely solitary existence extremely close to the city. Now, most of these tasks are automated, and the cribs have been secured by U.S. Coast Guard technology (presumably in a 2002 reaction to 9/11). Any craft that ventures into the security zone surrounding a crib sets off multiple alarms and sensors, which are directly linked to the Chicago Police Department.

Not too surprisingly, the lake's water is getting more and more polluted from water flowing into it from the city. This causes multiple problems for the water filtration system in Chicago. Plans are in the works to build new cribs further north and further out, in areas that aren't as polluted (yet).

Image via JeremyA.

Feeling thirsty? Need some advice? Email ask(at)chicagoist(dot)com.