Water Quality Monitoring
The Illinois Environmental Protection Agency (IEPA) is required to prepared a list of impaired waters every
two years to fulfill the requirements set forth in Section 303(d) of the federal Clean Water Act and the Water Quality Planning and Management regulation at 40 CFR Part 130. IEPA monitoring data is utilized to identify waters that do not meet applicable water quality standards or do not fully
support their designated uses.
Total Maximum Daily Load
The Clean Water Act also requires that a Total Maximum Daily Load (TMDL) be developed for each pollutant of an impaired water body. The establishment of a TMDL sets the pollutant reduction goal necessary to improve impaired waters. It determines the load,
or quantity, of any given pollutant that can be allowed in a particular water body. A TMDL must consider all potential sources of pollutants, whether point or nonpoint. It also takes into account a margin of safety, which reflects scientific uncertainty,
as well as the effects of seasonal variation. The IEPA maintains the status of TMDL reports for impaired waters.
Water Quality Monitoring Partners
In addition to the efforts of DuPage County, municipal, and township governments, several other organizations within DuPage County have worked to implement the pollutant reduction goals outlined in the various TMDL reports produced for Illinois' impaired
waters. These organizations include DuPage River Salt Creek Workgroup, Lower DesPlaines Ecosystem Partnership, and Fox River Ecosystem Partnership.