Water Quality

Water Quality


DuPage County provides watershed planning often resulting in flood control projects that include water quality components to comply with federal regulations. The Clean Water Act requires all municipalities, townships and unincorporated areas of DuPage County to comply with National Pollutant Discharge Elimination System (NPDES) permitting to restore and protect the water quality of the Waters of the State from pollutants associated with stormwater runoff. Stormwater Management offers all municipalities and townships within the County the opportunity to utilize the County’s water quality programs to comply with the requirements of NPDES, saving taxpayers millions of dollars based on economies of scale. The Clean Water Act also requires a Total Maximum Daily Load (TMDL) be developed for each pollutant of an impaired water body. It determines the load - or quantity - of any given pollutant allowed in a particular water body. A TMDL must consider all potential sources of pollutants - both point and non-point - while taking into account a margin of safety and the effects of seasonal variation.

Stormwater Permit

DuPage County is permitted to discharge stormwater to Waters of the State through its coverage under Illinois Environmental Protection Agency (IEPA) Permit No. ILR40, General NPDES Permit for Discharges from Small Municipal Separate Storm Sewer Systems. ILR40 includes six minimum control measures which are to be included in the County's stormwater management program:

  1. Public Education and Outreach on Stormwater Impacts
  2. Public Involvement / Participation
  3. Illicit Discharge Detection and Elimination 
  4. Construction Site Storm Water Runoff Control 
  5. Post-Construction Storm Water Management in New Development and Redevelopment
  6. Pollution Prevention / Good Housekeeping for Municipal Operations 

Each of these minimum control measures, as well as the overall Phase II Municipal Separate Storm Sewer System (MS4) permitting program, is summarized in DuPage County's Stormwater Management Program Plan.


Check out the Water Quality Archives for information regarding older water quality issues, such as presentations and seminars.

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