Hundreds of dead fish were found in a lake in the Village of Gages Lake and the park district says they are working with a treatment company and environmental authorities.
The Wildwood Park District said on Tuesday that it was aware of the sightings and reports of numerous dead fish at Valley Lake, which is located between Grayslake and Gurnee.
The park district said it was in communication with its treatment company and environmental authorities to address the issue.
Officials said the treatment company purposely did not overtreat the lake during their last two visits to keep the environment balanced and avoid a dissolved oxygen crash and fish kill.
The dead fish situation can “partially be attributed” to current low dissolved oxygen levels, possibly due to previous hot temperatures and sudden rain that can cause the lake to “flip.”
The Wildwood Park District said in an update on Wednesday that they were working with the Lake County Health Department and have been in contact with the Illinois Department of Natural Resources to identify the potential cause of the event and to assess current water conditions.
The Lake County Health Department reported they were able to take a dissolved oxygen reading at Valley Lake on Wednesday afternoon.
The reading was registering at values of 1.5 mg/L of dissolved oxygen at the surface and down to 0.6 mg/L, approximately a foot down.
Levels below 5 mg/L can typically begin to stress fish, meaning the current low levels would contribute to a fish kill.
Staff observed live fish as well near the surface, which will likely continue until oxygen picks back up. The fish are trying to stay near the slightly higher oxygen levels.
The park district said several contributors to the dissolved oxygen crash are possible.
Water temperatures are higher in the summer, causing water to hold less oxygen. Heavy rain events, such as the one that occurred on Monday, can bring in large amounts of organic material.
The large amounts of organic material can be oxygen-consuming, crashing the dissolved oxygen.
The park district said they are in remediation discussions with an organics company to address the fish removal and disposal on Thursday.
“We apologize for any inconvenience this may cause and will continue to provide updates as these efforts progress,” the agency said.
Residents in the area told CBS Chicago that the smell is horrible from the hundreds of dead fish.
“It’s terrible. I can’t even open my windows the first clear, low-humidity day to air out the house and I can’t. I’ve got to leave the air conditioning on,” Frank Mazzuca said.