| Causes and Sources of Impairment for the
East and West Branches of the DuPage River
Based on the 2006 Integrated Water Quality Report and Section 303(d) List |
| Potential Causes of Impairment | Potential Sources of Impairment | In-stream Effect |
| Sedimentation/Siltation | Site Clearance (Land Development or Redevelopment), Urban Runoff/Storm Sewers, Highways, Road, Bridges, Infrastructure (New Construction), impacts from Hydro-structure Flow Regulations/Modifications | Covering of stream bottom habitat with silt, cloudy water, difficult for fish to see prey, depletion of Oxygen needed by fish and macroinvertebrates |
| Total Suspended Solids | Contaminated Sediments, Municipal Point Source Discharges | Covering of stream bottom habitat with silt, cloudy water, difficult for fish to see prey |
| Breakdown of organic matter (from stream bank erosion, upland washoff, water treatment works and decaying aquatic vegetation) in stream, particularly behind dams, high rates algae growth and high water temperatures. | Channelization, Impacts from Hydro-structure Flow Regulations/Modifications, Urban Runoff/Storm Sewers, Municipal Point Source Discharges | Depletion of Oxygen needed by fish and macroinvertebrates |
| Total Phosphorus | Municipal Point Source Discharges, Urban Runoff/Storm Sewers, Runoff from Forest/Grassland/Parkland, Waterfowl, Specialty Crop Production, | Increased Algal Growth, Depletion of Oxygen needed by fish and macroinvertebrates |
| Total Nitrogen | Site Clearance (Land Development or Redevelopment), Urban Runoff/Storm Sewers, Road, Bridges, Infrastructure (New Construction), Streambank Modifications /destabilization, Loss of Riparian Habitat | Increased algal growth, Depletion of Oxygen needed by fish and macroinvertebrates |
| Chlorides
-Urban Runoff/Storm -Sewers, Municipal Point -Source Discharges
-Road deicing operations | Increased salinity | Bacteria, Public Health/Primary Contact with water, reduction of flora and fauna diversity as salt intolerant species are pushed out |
| Fecal Coliform | Urban Runoff/Storm Sewers, Source Unknown |
| Hexachlorobenzene | Contaminated Sediments | Toxic Substance - Automotive |
| Mercury | Contaminated Sediments | Toxic Substance - Heavy Metal |
| DDT | Contaminated Sediments | Toxic Substance - Pesticide |
| Oil & Grease | Source Unknown | |
| Aldrin | Contaminated Sediments | Toxic Substance - Pesticide |
| Silver | Contaminated Sediments | Toxic Substance - Metals |
| pH | Impacts from Hydro-structure Flow Regulations /Modifications | |
| Zinc | Urban Runoff/Storm Sewers, Municipal Point Source Discharges | Toxic Substance - Metals |
| Copper | Municipal Point Source Discharges | Toxic Substance - Metals |
