The South Lyons Township Sanitary District (SLTSD) is located in west-central Cook County, about 14 miles southwest of the City of Chicago as measured along the Stevenson Expressway (I-55). As shown in Figure 2, the SLTSD is generally bounded by 49th Street on the north, East Avenue on the east, the I-55 Stevenson Expressway on the south, and Brainard Avenue on the west.

The SLTSD was originally incorporated on August 15, 1959 as the Countryside Sanitary District in order to provide waste water disposal services to the then unincorporated region situated south of the Village of La Grange. In 1961, with widespread public concern over the need for potable water and other public services, the area residents voted to incorporate properties to form the City of Countryside. Following the formation of the City of Countryside, the Countryside Sanitary District subsequently changed its name to the South Lyons Township Sanitary District in order to avoid possible confusion with a the new municipality. The SLTSD encompasses an area of about 1,324 acres, which overlaps the political western Springs jurisdictions of the City of Countryside, the Village of La Grange, and a small portion of unincorporated Cook County. Land use within the SLTSD is largely mixed, with about sixty-two percent (62%) residential, and about thirty-eight percent (38%) commercial/industrial. The land surfaces 5 a N countryside are considered to be fully developed for the current zoned uses. Given the lack of large undeveloped land areas, future development will likely involve the redevelopment of existing land uses. With the current land use characteristics, radical changes in land use are not expected, and only minor changes to sewer use are expected to occur as a result of future redevelopment activities.

The map exhibit provided depicts the relative positions of the sauging equipment installed for the study. The flow meters were installed in manhole structures located immediately upstream of the connection to the MWRD interceptor manhole. The rain gauge location is also shown relative to the Plainfield Road and East Avenue intersection. The location for each gauging point, defined by an adjacent street address has been listed in Table 10.