Illinois 2012 Beachwater Quality Summary
Reported Sources of Beachwater Contamination
(number of closing/advisory days)
- 331 (99%) unknown contamination sources
- 2 (1%) stormwater runoff
- 1 (<1%) wildlife
Illinois has 52 public swimming beaches along approximately 60 miles of Lake Michigan shoreline. The Illinois Department of Public Health (IDPH) administers the state’s coastal beach monitoring program.
What Are the Water Quality Challenges and Improvements in Illinois?
Improved Water Quality at North Point Marina Beach
Beachwater quality at North Point Marina Beach in Lake County was historically poor; the yearly percent exceedance rates from 2005 to 2011 ranged from 34% to 83%. In spring 2011, the Lake County Health Department received Great Lakes Restoration Initiative funding to plant native vegetation, restore the dunes, and remove invasive species with the goal of reducing the seagull population and improving water quality. Although work is still ongoing (scheduled to be completed fall 2013), the initial results are promising; the exceedance rate was 12% for the 2012 season.
Improved Water Quality at Elder Lane Beach
Elder Lane Beach previously had some of the highest exceedance rates in Illinois. In 2011, beachwater monitoring samples exceeded state standards 54% of the time. The village of Winnetka investigated and detected 15 private-home sewage systems that crossed into the stormwater drainage system, which releases into Lake Michigan at Elder Lane. These sewage systems have been repaired, and water quality in the area has improved: In 2012, Elder Lane Beach samples exceeded standards 12% of the time.
Green Infrastructure Planned for Rainbow Beach
Rainbow Beach has historically suffered poor water quality. During the 2012 monitoring season, its exceedance rate of 28% was the highest in Illinois. The Chicago Park District received a Great Lakes Restoration Initiative grant in 2012 from the U.S. EPA to install a green stormwater filtration system to capture and treat runoff at Rainbow Beach, which should reduce stormwater volume and improve water quality in the area. The project is currently in the design phase and will be installed after the 2013 beach season.
Improving Beachwater Quality in Chicago
In 2012, the Chicago Park District began using predictive models at 14 beaches: Juneway, Rogers, Howard, Jarvis/Fargo, Hartigan, Leone/Loyola, Foster, Montrose, Oak Street, Ohio Street, 12th Street, 31st Street, 63rd Street, and Calumet. Parameters include wave height, turbidity, rainfall, wind speed and direction, and solar radiation. In 2012, advisories were issued when the predicted bacteria level for E. coli was above 235 cfu/100 ml.
Two beaches in Chicago, 63rd Street Beach (Jackson Park) and 57th Street Beach, routinely exceeded water quality standards in the past. A large number of seagulls are known to contribute to the fecal contamination at these beaches. Using border collies during the beach season to harass gulls every day from dawn to dusk has proved to be an effective means of improving water quality at these beaches.
What Does Beachwater Monitoring Show?
In 2012, Illinois reported 65 coastal beaches and beach segments, of which 20 (31%) of which were assigned a monitoring frequency of once a day, 28 (43%) more than once a week, and 3 (5%) once a week, and ; 14 (22%) were not assigned a monitoring frequency. In 2012, 10% of all reported beach monitoring samples exceeded the state’s daily maximum bacterial standard of 235 colonies/100 ml. The beaches with the highest percent exceedance rates of the daily maximum standard in 2012 were Montrose Dog Beach (38%), Rainbow Beach (30%), Jackson Park Beach (63rd/64th St. Beach) (27%), Montrose Beach (25%), and 31st Street Beach (21%), all in Cook County. Cook County had the highest exceedance rate of the daily maximum standard in 2012 (10%), followed by Lake (9%). NRDC considers all reported samples individually (without averaging) when calculating the percent exceedance rates in this analysis. This includes duplicate samples and samples taken outside the official beach season, if any.
Illinois Percent of Samples Exceeding the State's Daily Maximum Bacterial Standard for 47 Beaches Reported 2008-2012*
* Please note that only samples from a common set of beaches monitored each year from 2008-2012 are included in the bar chart.
What Are Illinois's Sampling Practices?
The monitoring season extends from Memorial Day to Labor Day. Samples are taken in water that is knee to waist deep. Many coastal swimming beaches in Illinois are sampled seven days a week, as Illinois believes daily monitoring is most protective of public health. Areas of shoreline that are not used for swimming because they are rocky or otherwise unsuitable are not monitored. Daily monitoring is conducted when a swim ban or advisory is issued. States that monitor more frequently after an exceedance is found and after pollution events will tend to have higher percent exceedance rates and lower total closing/advisory days than they would if their sampling frequency did not increase after an exceedance or a pollution event.
How Many Beach Closings and Advisories Were Issued in 2012?
Total closing/advisory days for 228 events lasting six consecutive weeks or less decreased 31% to 334 days in 2012 from 483 days in 2011. For prior years, there were 508 days in 2010, 576 days in 2009, and 534 days in 2008. There were no extended or permanent events in 2012. Extended events are those in effect more than six weeks but not more than 13 consecutive weeks; permanent events are in effect for more than 13 consecutive weeks. For the 228 events lasting six consecutive weeks or less, 91% (305) of closing/advisory days were due to monitoring that revealed elevated bacteria levels, and 9% (29) were preemptive due to other, unspecified reasons.
How Does Illinois Determine When to Warn Visitors About Swimming?
Depending on the managing authority for coastal beaches, both advisories and swim bans are issued. The water quality standard in Illinois is an E. coli single-sample maximum of 235 cfu/100 ml. No geometric mean standard is applied when making swim ban and advisory decisions. Beachgoers can find advisory information on the Chicago Park District website.
In most jurisdictions, either a swim ban or an advisory is issued if one sample exceeds the single-sample standard.5 The only exceptions are beaches managed by the Wilmette Health Department (the Gillson Park beaches and Langdon Beach), the Winnetka Park District (Tower, Maple, and Elder beaches), and Lake County (North Point Marina Beach and Illinois Beach State Park). Two samples are taken daily at these beaches, and if one sample exceeds the standard, a resample is taken before a swim ban is issued. If both samples exceed the standard, a swim ban is issued without resampling. In 2011, the Chicago Park District posted an advisory at its beaches when sample results were between 235 cfu/100 ml and 1,000 cfu/100 ml, and a ban when sample results exceeded 1,000 cfu/100 ml. In 2012, the Chicago Park District began posting advisories when sample results exceed 235 cfu/100 ml and bans when there is a sewage spill.
Beach managers may preemptively issue swim bans or advisories because of rain or other factors.
The Lake County Health Department uses a predictive model called SwimCast to make swim ban and advisory decisions at Waukegan South Beach, Forest Park Beach in Lake Forest, and Rosewood Beach in Highland Park. At a minimum, predictions are generally made at 9 a.m. and 1 p.m. and whenever hydrometeorological conditions change. For each beach where the SwimCast system exists, similar but slightly different predictive models are used. These models predict beachwater conditions on a real-time basis, in contrast to standard culture methods for quantifying bacteria. When culture methods are used as the basis for issuing swim bans and advisories, health warnings are not issued until at least 24 hours after samples are taken due to the time required to process and read the samples. In a sense, using culture methods to issue swim bans and advisories is akin to using yesterday’s bacteria density to predict today’s. Studies have shown that SwimCast provides a more accurate assessment of current beachwater quality than does the prior day’s bacterial density.
SwimCast models produce a 99% confidence interval—that is, a lower and upper bound of bacterial concentrations between which the actual bacteria concentration is expected, with 99% confidence, to lie. At all beaches where the SwimCast model is used, the protocol for determining swim bans and risk advisories is the same:
- A swim ban occurs when the lower bound of the 99% confidence interval is above 235 cfu/100 ml. Under a ban, the beach is posted with a red flag. This is the highest-risk condition.
- When the average prediction and upper bound of the 99% confidence interval are above 235 cfu/100 ml but the lower bound is below 235 cfu/100 ml, this is considered a moderate- to high-risk condition and the beach is posted with a red flag.
- When the upper bound of the 99% confidence interval is above 235 cfu/100 ml but the average prediction and the lower bound of the 99% confidence interval prediction are below 235 cfu/100 ml, this is considered a moderate-risk condition and is posted as an advisory at the beach.
- When the upper bound of the 99% confidence interval prediction is below 235 cfu/100 ml, this is considered a low-risk condition and is posted with a green flag.
In the Chicago Park District, intensive data collection began in 2011 for model development at five additional beaches: Foster, Montrose, Oak Street, 63rd Street, and Calumet. The district is using models at several of these beaches to make swim ban and advisory decisions in 2012.
Illinois 2012 Monitoring Results and Closing/Advisory Days