WATER QUALITY, CHEMISTRY, AND HYDROLOGY OF SALT CREEK IN NORTHEASTERN ILLINOIS

Salt Creek flows through the metropolitan area of Chicago and into the Des Plaines River. Its urban environment provides multiple sources of contamination, including storm runoff, combined sewer overflow, and wastewater treatment plant discharge. The purpose of this study is to determine how water chemistry changes downstream, whether the presence and levels of metals meet IPCB (Illinois Pollution Control Board) and EPA water quality standards, and how water chemistry changes during periods of storm flow and base flow. The study area consists of 10 sites along a 37 km stretch of Salt Creek. Water samples were taken every other week during June, July, and August of 2014. Six of these sites are located near USGS gaging stations, and corresponding hydrographs were collected to determine hydrological characteristics of the creek such as storm flow and base flow conditions. Hydrographs show Salt Creek as a “flashy” stream, a result of being in an urban area with a large amount of impervious space. Due to its “flashy” behavior, the frequency of flooding and the rate of erosion have increased. Analysis of water samples was done with an X-Ray Fluorescence spectrometer (XRF) to determine concentrations of metals (As, Cu, Fe, Ni, Pb, Zn), and other ions (Ca, Mg, Na). Other measurements included conductivity, temperature, and pH. Concentrations of As and Pb above IPCB limits were found throughout the study area and concentrations of Fe above IPCB standards were found in more downstream regions during both periods of storm flow and base flow. Fe was more often present during periods of storm flow. Concentrations of Cu, Ni, and Zn were generally below IPCB limits. Consistently high concentrations of As, Pb, and Fe were found in samples taken near the city of Elmhurst, and several possible industrial point sources have been identified. Two upstream sites near Rolling Meadows and Elk Grove had conductivity measurements above EPA standards set for the creek. Rolling Meadows also had consistently higher values for Ca, Mg, and Na.