Intense rainfall a concern at Environment Board meeting


Linus Höller/The Daily Northwestern

The Environmental Board is looking to improve Evanston’s preparedness for heavy rain, as the city’s current storm sewers are only designed for a five-year rain event.

Linus Höller, Reporter

Dave Stoneback, director of Evanston’s Public Works Agency, is concerned about the rain.

“Rainfall conditions will probably only get worse with climate change,” he cautioned at the city’s Environment Board meeting on Thursday evening.

Evanston’s storm sewers are not ready for a major downpour, Stoneback said. The existing system has only been designed to handle the amount of water from a five-year rain event.

Nowadays, rainfall of this intensity occurs on average every three years due to shifting precipitation patterns as a result of the globally changing climate.

“The worst case is that the water not only floods the streets but goes all the way up to people’s homes, pours in through the basement windows and flows in under the front door,” Stoneback said.

The scenario awakes bad memories from the summer of 1987, when a downpour of 13 inches in just nine hours flooded many residents’ basements, Stoneback said.

Since then, $210 million have gone towards a sewer improvement plan, which has been “fairly successful,” according to Stoneback.

“Our main concern now is standing water on the streets rather than water in people’s basements,” he said.

To further improve the city’s preparedness for torrential rainfall, an external specialist will create a hydrologic and hydraulic model of Evanston over the course of the next few years. The proposal is expected to be released in December, with the selection of a contractor four to six months later.

What will follow is a two-year period of intense measurements using rain gauges throughout the city and flow meters in the sewer systems to help identify areas which need the most improvement.

Stoneback recalled that when the city had its own flow meters, it was “just awful.” He said maintenance costs would far outweigh those for a one-time contractor. Stoneback admitted there is one catch to the plan.

“If there’s a dry year, then we’ve paid a whole lot of money for nothing,” he said.

Stoneback said that the city would not be waiting for the completion of a plan before taking action. The use of so-called “green infrastructure,” already implemented in parts of the city, will be further pushed — especially near the lakefront, as these are the lowest-lying areas of Evanston. One area of special focus will be the upgrading of parking lots, replacing impervious concrete surfaces with permeable pavement alternatives.

Permeable pavement is not new to Evanston, but there have been major issues with its maintenance in the past.

“We have put a bunch of green infrastructure in, but then there is never any funding to maintain it,” Stoneback said.

According to a draft of the city’s new “Stormwater Management Guide,” maintenance for permeable pavement is needed to ensure its functionality.

“Over the lifetime of the permeable pavement system, there will be a need to clean any sediment, soil, dirt and debris from the permeable pavement in order to maintain a sufficient infiltration rate,” the document states.

The city recently issued an ordinance against blowing leaves onto the roads to avoid clogging the storm drains. Environmental Board member Cherie Fisher said flyers will be passed out to garden contractors outlining that this practice is illegal in Evanston.

“If you have some extra,” Fisher joked, “we’re exactly the kind of people to put these sort of flyers on people’s windshields.”

Looking forward, the city plans to develop a regular schedule to routinely sweep the parking lots and to replace the chips.

Stoneback said at the meeting that he hopes the new routine will save a substantial amount of money.

“We did not do this right and now we are re-starting,” he said.

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