Weather Updates

Quicker warnings coming on Lake Michigan safety

Sections Oak Street Beach are packed with teenagers Friday June 3 2011 Chicago. A number medical assistance calls were made

Sections of Oak Street Beach are packed with teenagers Friday, June 3, 2011, in Chicago. A number of medical assistance calls were made to assist beach-goers who were intoxicated, according to police officers patrolling the area. | John J. Kim~Sun-Times

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Updated: July 2, 2012 9:46AM

Beach lovers will find out faster than ever before this summer if it’s safe to take a dip in Lake Michigan, as the Chicago Park District improves its measuring procedures.

With the beach season kicking off Friday, the city announced it is phasing out as its first line of defense an old system that relied on testing E. coli bacteria levels in Lake Michigan waters to issue swim bans.

Instead, swim bans and advisories will be based on real-time intelligence on beach conditions as well as a new predictive analysis model. That means not waiting 18 hours for lab results.

The new system is expected to result in fewer outright bans but possibly more swim advisories. Last year, swimming bans totaled 56, while 134 advisories were issued.

Rather than relying on lab testing — as has been the case for years — bans will be issued when the park district is notified about sewer overflows, according to the Chicago Park District. As they have before, bans will be issued for severe weather, lightning and high waves.

Cathy Breitenbach, the park system’s Director of Lakefront Operations, said the new system is used at other Great Lakes beaches and gets a nod from the U.S. Environmental Protection Agency. And it’s more accurate, she says.

“We found [the old system] overly restrictive and prone to inaccurate results,” Breitenbach said. Under the old system, the park district ordered a swimming ban after water testing showed more than 1,000 colony forming units of E. coli per 100 milliliters of water.

The park district will be changing the way it determines when to issue swim advisories as well — when swimmers aren’t prohibited from the lake but advised it may not be healthy to go in.

Over the years, swim advisories — which alert beachgoers when bacteria levels are higher — have been issued using the same testing method. The advisories are given out when 235 or more colony forming units of E. coli have been detected. That is based on studies showing a 75 percent chance that at least eight out of 1,000 people will come down with gastroenteritis, an infection causing diarrhea, nausea and vomiting

While that testing will continue, the park district is rolling out a new detection system this season that will provide more timely results to issue such advisories. Known as predictive modeling, the new system uses weather data to predict bacteria levels in what park officials call “real time.”

While lab testing meant waiting 18 hours for results and then issuing an advisory the next day, the new system relies on real-time data that will be used at beach-opening time to determine whether an advisory should go out.

The new system will be used at 16 of the 24 designated swimming beaches along Chicago’s lakefront, the park district says, noting they hope to eventually have the modelling in place at all swim beaches down the line.

In the meantime, old-fashioned lab testing will continue as a backup for advisories.

The predictive modeling system is paid for by a $245,420 grant from the U.S. EPA’s Great Lakes Restoration Initiative. Lab costs for testing are $85,000 per beach season with about half coming from federal grant monies that are passed through the state’s public health department and the other half from the park district’s budget.

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