The Illinois EPA conducts a wide variety of water quality monitoring programs which have sampled approximately 3,500 stream stations. Nearly 1,000 of these stations have been sampled for biological, chemical and instream habitat data as well as stream flow. Water quality monitoring programs consist of a combination of fixed station networks and intensive or facility-related stream surveys in specific watersheds.
Illinois EPA, with contractual assistance provided by the U.S. Geological Survey and Illinois State Water Survey, operates an Ambient Water Quality Monitoring Network (AWQMN) consisting of 146 fixed stations to support surface water chemistry data needs. Integrated water column samples are collected on a six week sampling frequency and analyzed for a minimum of 55 universal parameters including field pH, temperature, specific conductance, dissolved oxygen, suspended solids, nutrients, fecal coliform bacteria, and total and dissolved heavy metals. Additional parameters specific for the station, watershed, and/or subnetwork within the ambient network are also analyzed. Where stream flow is available from the U.S. Geological Survey (USGS), water quality data are analyzed for flow-adjusted water quality trends.
Illinois has more than 580 navigable miles of Mississippi River shoreline. Until 1999, the Agency only maintained four active AWQMN stations along this entire river segment. Samples were collected frequently at stations at Fulton, Elsah and Thebes, and nine times a year at Keokuk. Beginning in 2000, seven additional monitoring stations were located on the river, with approximately 50 miles between each station. Above St. Louis these stations are located at locks and dams, while the river below St. Louis is sampled from existing boat access ramps. All stations are sampled on a quarterly basis.
Since October 1985, Illinois EPA has operated a Pesticide Monitoring Subnetwork to expand screening for toxic organic substances. Fifteen common herbicides and organophosphate insecticides currently used in agricultural production practices are included for water column analysis. The Pesticide Monitoring Subnetwork consists of 20 AWQMN stations that are adjusted annually to provide additional monitoring coverage in conjunction with the Intensive Basin Survey program. Sampling is conducted during three of the nine AWQMN sampling cycles and consists of one pre-application collection (March to mid-April) and two samples collected in the post application period (mid-April to July). Post pesticide application collections are coordinated with farming activities occurring locally near the AWQMN collection site.
Illinois EPA conducts Facility-Related Stream Surveys consisting of the collection of macroinvertebrate, water chemistry, stream flow and habitat data upstream and incrementally downstream from municipal and industrial wastewater treatment facility discharges. Facility-Related Stream Survey information is used to evaluate water quality impacts and the need for additional wastewater treatment controls. Data are also used to characterize the existing and potential aquatic resource of the receiving stream, determine whether there is significant biological impact on the receiving stream and to support the Bureau of Water's National Pollutant Discharge Elimination System permit reissuance activities.
Intensive river basin surveys are conducted on a five-year rotational basis in cooperation with the Illinois Department of Natural Resources (IDNR). These intensive river basin surveys are a major source of information for annual 305(b) assessments. Illinois has 33 major river basins within its borders. Stations sampled by Illinois EPA and IDNR are selected on the basis of where intensive data are currently lacking or historical data need updating. Water chemistry and biological (fish and macroinvertebrate) data along with qualitative and quantitative instream habitat information including stream discharge are collected to characterize stream segments within the basin, identify water quality conditions, and evaluate aquatic life use impairment. Fish tissue contaminant and sediment chemistry sampling are also conducted to screen for the accumulation of toxic substances.
Fish samples collected at intensive river basin survey stations are analyzed for 14 chemical contaminants as part of the Fish Contaminant Monitoring Program. Fish samples are collected and analyzed from approximately 50 stations on Illinois' rivers and streams on an annual basis.