Working together in a prioritized and concentrated manner, Mayor Robert Kolosh from Thornton, Mayor Rich Hofeld from Homewood, and Mayor Don De Graff from South Holland met recently with David St. Pierre, Executive Director of the Metropolitan Water Reclamation District (MWRD), to discuss immediate and effective solutions to the odors occurring in the vicinity of MWRD’s Thornton Reservoir. St. Pierre provided valuable insight regarding the initial challenges presented in operating such a large tunnel and reservoir system and committed to the implementation of a series of odor mitigation improvements, several of which are already in process.

According to St. Pierre, “MWRD is well aware of the odor issues, having received a good number of initial calls from local businesses and residents immediately after the reservoir initially went online in 2015. After the creation of an internal task force, several short-term actions were taken at that time by MWRD to ensure that the problem was minimized. Consequently, the beginning of the Thornton Reservoir’s first full summer proved uneventful.”

In July of 2016, the southland area received up to 6” of rain in a very short duration event. Per MWRD’s assessment, this massive amount of water feeding into the reservoir displaced air in the deep tunnel system and pushed the air out of the tunnels at a rate which overwhelmed the short-term mitigation actions taken previously. This rain event resulted in numerous complaints from the displaced air and generated odor readings at MWRD monitoring stations. Similar problems were experienced with another torrential rain event in August of 2016 and unfortunately, in a number of lesser rain events leading into the fall season.

Because the initial mitigation procedures have proven to be insufficient, St. Pierre and MWRD officials have since commenced the revision of their existing operating plans. These short and long term measures include the following:

• MWRD has utilized the Transitional Reservoir water (west lobe of quarry) to freshen the water in the Thornton Reservoir (north lobe of quarry). This operating strategy, when enacted, has reduced odor levels below detection in the Thornton Reservoir, accounting for the success between the spring and the recently discovered problems.
• MWRD immediately installed odor monitoring systems around the perimeter of the reservoir to measure and detect system effectiveness. The detection system will be used in the long term to activate misting mechanisms that will neutralize odors in the air before leaving the tunnel system.
• MWRD designed and is in the process of installing additional misting mechanisms around the perimeter of the reservoir and also at two drop shaft locations. These mechanisms are currently under construction and will be in service December 1, 2016.
• MWRD installed landscaping around the perimeter of the Thornton Reservoir to act as a wind block year round to minimize the winds which can carry odor from the site.
• Solar powered circulators are being used to oxygenate the water in the reservoir which, if oxygenated, will create an odor buffer at the surface. The number of units required has nearly tripled, from 7 to 20, in order to ensure that this technology will be effective. These additional units will be installed during the winter of 2016-17 as the reservoir needs to be dry to do so.

Upon observing the severity of the problem over the last several rain events, St. Pierre conveyed that additional immediate actions are being taken by MWRD:

• MWRD has entered into an emergency contract to install temporary misting mechanisms at drop shaft locations with high odor readings.
• Operating procedures have been modified to close gates, pump down and flush the tunnel system completely, dispelling odor causing debris that is trapped in the tunnels.
• MWRD has adjusted odor call response protocols to ensure responsiveness to residents, to track the odor source effectively, and to properly mobilize odor neutralizing resources to offending site locations.

Executive Director St. Pierre reiterated to each Mayor that “MWRD will continue to monitor and evaluate the measures taken and adjust as needed to minimize odor emissions from the system. MWRD offers its apologies for the odors that have been generated from the system here at the onset of its operations. Because the Thornton Reservoir is part of a large, comprehensive system, which provides significant benefits to all residents in the southland area, it will take some time for the District to better understand how to fully and effectively operate it for all purposes, including odor elimination. MWRD will continue to strive to operate the system better and to employ all reasonable efforts to eliminate the odors.”