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Evanston Raw Water Intake Replacement

Reliable water access for half a million people in Illinois depends on the City of Evanston¡¯s water treatment plant. A raw water intake pulls Lake Michigan water into the plant to treat it to drinking water quality standards. One of the City¡¯s three intakes¡ªa 36/42?inch (91/107-centimetre) line built in 1909¡ªhad reached the end of its useful life and was losing capacity, putting pressure on a system that serves Evanston and nine neighboring communities.

To protect long?term water reliability, the City turned to our team to design a modern intake that would replace the old intake and meet today¡¯s demands and tomorrow¡¯s growth. We designed a new 5,500?foot (1,829-metre) long, 60?inch (152-centimetre) diameter raw water intake equipped with a lakebed inlet structure and onshore system upgrades. Our services spanned across preliminary and final design, cost opinions, hydraulic modeling, permitting, and construction?phase engineering.

Harsh winters call for creative solutions to resist icy waters. Using computational fluid dynamics (CFD), we modeled the intake¡¯s hydraulics to balance flows and reduce the risk of ice building up on the intake. A heating system coupled with temperature monitoring provides additional protection that can be adjusted to conserve power in warmer weather.

CFD also helped us design the intake so that the water flows in at the right speed to avoid pulling sediment into the treatment plant. Invasive quagga mussels can build up on intakes and reduce capacity. To address this, we included a chlorine feed line to bring the City¡¯s existing chemical feed system to this intake, which makes the intake less inviting to the mussels.

The new intake will provide the City with an overall firm supply capacity of 120 million gallons (454 megalitres) per day, strengthening the regional water supply and providing clean, dependable drinking water for generations to come.