Water Quality and TMDL


The quality of the water in the Salt Creek relies on many factors. The two most important factors are the water entering the creek and the physical condition of the creek. The water entering the creek comes from two sources, effluent from point sources, and runoff from non point sources.

Point source effluent comes from pipes discharging into the creek. The effluent comes from publicly owned wastewater treatment plants (POTW, publicly owned treatment works), industrial discharge, and storm sewers. In most cases the quality and volume of discharge from these sources is regulated by the EPA by means of NPDES permits. These NPDES (National Pollution Discharge Elimination System) permits are administered by the EPA, or the state EPA, in our case, the Illinois EPA.

Non Point Source (NPS) pollution can come from storm sewer pipes, or from runoff from the surface. Usually water entering the storm sewers is not treated and carries pollution from our streets. This pollution can be in the form of chloride from salting our roads in winter. It can be from oil and gas leaks from our cars and service stations. It can come from people dumping liquids or garbage into storm drains. It can come from leaf and grass debris in the streets. Yes, even too much leaf and grass litter can cause pollution.

NPS pollution can also come from runoff from our yards. Washing your car in the driveway sends oily, soapy water into the storm water system. Pet waste that is not picked up ends up washing into the storm water system. Applying herbicides or pesticides to the lawn or garden before a rain storm will result in those pesticides and herbicides getting washed off and into the storm water system. Applying more than the recommended amount of pesticides and herbicides can cause burnout in the lawn or garden, and the excess ends up in the storm water system. As individuals we have a big impact on water quality in the Salt Creek.

The physical condition of the stream bed plays an important role in water quality. Eroding stream banks allow excess sediment to enter the stream, reducing visibility and blocking sunlight. Fish need plants to provide cover from predators, sometimes for food, and as food for the invertebrates that they eat. Stones and rocks in the stream also provide hiding places and the water rippling over the rocks adds oxygen to the water, also necessary for plant and animal life. Shade from trees helps to keep the shallow water cooler in the summer. There are many physical factors that impact the health of the Salt Creek. They can work together to improve the water quality, or they can work against it.

With pollution entering the Salt Creek from all these sources, how can we achieve water quality standards? Well, we need to control the total amount of pollution entering the stream. NPDES permits were designed to limit the amount of pollution from waste water treatment plants, and the system worked pretty well. Our streams are in much better condition than before the Clean Water Act mandated the permitting process. Now, NPS pollution is the main reason the Salt Creek does not meet water quality standards. To address this issue we have the TMDL.


What is a TMDL? TMDL is short for Total Maximum Daily Load. It is an analysis of the maximum amount of pollution a water body can receive and still meet water quality standards. This analysis, known as ‘the TMDL’, sets pollution reduction goals to improve impaired waters.

The Illinois Environmental Protection Agency, IEPA, is responsible for setting standards and monitoring water quality in Illinois. The TMDL process for the Salt Creek began in 2000. A consultant was contracted by the IEPA to study the impairments to the Salt Creek and to come up with an implementation plan to meet water quality standards. Their draft TMDL for the Salt Creek was published in 2003 and made available to interested parties. Public hearings were held to discuss the plan and provide a means for public participation in the TMDL process. During the hearings many questions and concerns were raised by the sanitary district operators and by various environmental groups. At the same time the draft TMDL for the East Branch of the DuPage River was made available and public hearings were held. The East Branch and the Salt Creek had similar impairments, and the same questions and concerns were raised about both TMDL’s. Since many of the same stakeholders were involved in both watersheds, a TMDL workgroup was formed. Stakeholders from the West Branch of the DuPage River also joined the workgroup, as their TMDL process began in 2002.

The TMDL workgroup began meeting in the spring of 2004 to work out a plan to improve the water quality of these streams. Even though most people think of the sanitary district sewage treatment plants (POTW, or publicly owned treatment works) as the main polluters of our streams, careful analysis of the data showed that the POTW’s in most cases exceeded their water quality standards and that the streams had the highest level of pollutants following a storm event – heavy rain or snowfall. Pollution in the streams is caused by storm water runoff, a non point source (NPS) of pollution. Since the pollution is coming from many sources throughout the watershed, it will take the work of many people and all communities in the watershed to improve the water quality of the Salt Creek and DuPage River.

On Nov. 17, 2004, the TMDL workgroup invited decision makers from all communities in the three watersheds to a meeting where these findings were presented along with some preliminary plans. All communities were asked to make a commitment to improve the water quality in these streams by working with the TMDL workgroup.