Chloride Variance – Important Update for Members Partially in the Lower Des Plaines River Watershed

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NPDES permit holders, including municipal, industrial, MS4s, and transportation agencies, that discharge to the Chicago Area Waterway System (CAWS) and the Lower Des Plaines River watersheds are seeking a time-limited water quality standard (TLWQS) for chlorides from the Illinois Pollution Control Board (IPCB). This is more commonly referred to as the Chloride Variance.  If approved by the IPCB, the TLWQS will not change the chloride Water Quality Standard of 500 mg/L but provide the permitted dischargers 15-years to implement chloride Best Management Practices (BMPs) as means of meeting the chloride standard. The Joint Submittal Petition, prepared principally by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC), provided details on the need for the TLWQ, required chloride reduction BMPs, and reporting requirements.

The Illinois Environmental Protection Agency (IEPA) is encouraging all permit holders located in the CAWS and Lower Des Plaines River  watersheds to become signatories to the Petition.  Several of our DRSCW members have portions of their jurisdictions that fall within the Lower Des Plaines River watershed.  See Table 1 for DRSCW municipalities with area in the CAWS/Des Plaines River Watershed.  Based on discussions with the IEPA, the DRSCW is recommending that these members file a Notice of Filing/Certificate of Service with the IPCB and sign-on to the Petition for the area located within the Lower Des Plaines River watershed.  Failure to participate in the Petition could result in being found in violation of your ILR40 Permit:  General NPDES Permit for Small Municipal Separate Storm Sewers (Part III. D).

More information on the Chloride TLWQS and the documents filed by MWRDGC with the IPCB can be found at:


Table 1. DRSCW municipalities with area in the CAWS/Des Plaines River Watershed


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The mission of the DRSCW is to bring together a diverse coalition of stakeholders to work together to preserve and enhance water quality and stream resource quality in the East Branch DuPage River, West Branch DuPage River, Salt Creek, and their tributaries.

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