Bacteria counts low at Winnetka’s ‘worst’ beach
Updated: August 6, 2012 6:21AM
The Winnetka Park District has seen a dramatic improvement in water quality at Elder Lane beach since the village pinpointed and repaired locations where discharge from sanitary sewers was infiltrating the stormwater drainage system that discharges into Lake Michigan near that location.
The history of high bacterial counts and frequent closings at Elder Lane beacn had flagged the beach as the worst among Illinois’ 52 public swimming beaches along Lake Michigan in the latest “Testing the Waters” report from the Natural Resources Defense Council. The report was published in 2011 based on data from the prior year submitted to the Illinois Department of Public Health.
In 2010, three out of five samples collected at Elder Lane beach between Memorial Day and Labor day showed levels that exceeded the standard of 235 colony-forming units per 100 millimeters of water, or about one-fifth of a pint. Last year, Elder Lane beach in north Winnetka was closed 10 of the first 16 days of the swimming season due to e Coli counts that exceeded safe-to-swim levels.
But since Winnetka beaches opened June 9, e Coli counts at Elder Lane have been far below 2010 and 2011 levels and the threshhold that prompts the park district to ban swimming. None of the park district’s four swimming beaches, including Tower Road, Maple Park and Lloyd Park, have been closed due to high bacterial counts so far this year.
By law, authorities need only post an advisory warning when bacterial counts exceed 235 colony-forming units and aren’t required to close the beach until counts reach 1,000. However, the Winnetka Park District has used the stricter standard in making its determinations.
According to figures released by the park district, counts have ranged from one or less on six days in June to a high of 69.5 on June 26, still well below the level where a beach closing is recommended. The park district began collecting samples in early spring to gauge the impact of the sewer corrections.
Over the past few years, the Winnetka Park District and the Village of Winnetka consulted with the Illinois Department of Public Health and researchers from the University of Illinois-Chicago in an attempt to identify the source of the bacteria. “The investigations revealed that a significant source, but probably not the only source ... is likely the storm sewer discharge located directly adjaent to the swimming beach,” noted the village on its website. A sanitary sewer probe, conducted with cameras and confirmed with dyes, identified 15 locations to the north of Elder Lane beach where sewage was entering the storm water system, either through leaks or cross-connections related to the age of the infrastructure.
The majority of the locations were private service pipes serving single-family homes and homeowners were required to repair the defects. The village also identified and repaired two instances of leaking village pipes.
“These cross-connections generally produce minor discharge volumes in the overall scheme of things, but their effects tend to be concentrated during periods of dry weather, when overall volumes in the storm sewer system are very low.” noted the village.
Recent news coverage drawing from NRDC’s last report in 2011 prompted the park district to issue a release last week assuring beach patrons that the water is safe.