CSO Public Notification Plan

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flooding on street[1] 

Public Notification Plan
February 10, 2004
City of Evanston NPDES Permit No. ILM580002

Identifying the Affected Public

The City intends to solicit comments and feedback from the affected public in development of the Combined Sewer Overflow (CSO) Public Notification Plan. The City considers the affected public to include governmental organizations, civic groups, recreational groups or any public citizen with an interest in or responsibility for the condition of the Chicago Area Waterway System (CAWS). Currently, the City identified the following organizations to be among the affected public: the USEPA; the IEPA; the MWRDGC; the Village of Skokie; the Skokie Park District Rowing Center; the Evanston Ecology Center; and the Evanston Environmental Board. The identified affected public will be invited to the public meeting that will be held on March 31, 2004. Comments and feedback will be solicited at that time. Advisories about the planned public meeting will be available on the City webpage, through the local news media, and direct notification when possible.

The City’s coordination with the MWRDGC

The City intends to coordinate the CSO Public Notification Plan in conjunction with the MWRDGC since the occurrence of CSOs is directly impacted by the operation of the MWRDGC sewer system. As such, the MWRDGC is aware of when CSO events occur and will display the occurrence of CSOs on their website. Additionally, the City will post signage at the City’s CSO Outfall locations, not posted by the MWRDGC, with signs similar to those being developed by the MWRDGC and the City of Chicago.

Web Page

The City will create a web page on the City’s website that will link to the District’s website. It is our understanding that the District’s website will include an electronic “Address Book” that will contain a list of email addresses of interested parties. These parties will be sent an email alert in the event of a CSO or diversion to Lake Michigan. The District web page will inform the general public of the occurrences of CSOs on the Chicago area waterways system. The District website will contain a color-coded graphic representation of the waterways depicting the occurrence of CSOs and the waterway diversions to Lake Michigan. Upon occurrence of a CSO in a given waterway segment, the color of the segment shown on the map will be changed from blue to red. The District has indicated that they will update the map on a daily basis between 5 a.m. and 6 a.m. to reflect CSO/floodwater discharge activity in the preceding 24-hour period. It will provide the public with a rolling seven-day record of CSO/floodwater discharge events in the Chicago area waterway system. The seven most current daily maps will be retained on the website with the oldest being deleted when a new map is added. A user will be able to select and display any one of the seven maps stored on the web page at a given time. In addition to the graphic map display, limited general information regarding CSOs and floodwater discharges to Lake Michigan, along with their implications, will be included for informational purposes. What is a combined sewer overflow (CSO)? A CSO is a discharge from a combined sewer system directly into a waterway. A combined sewer system is designed to collect a mixture of rainfall runoff, domestic and industrial wastewater in the same pipe for conveyance to a wastewater treatment plant. CSO may occur during heavy rainfalls when the inflow of combined wastewater exceeds the capacity of the combined sewer system and the wastewater treatment plant. The CSO outfalls to the waterway act as relief points for the excess flow in the sewers, thereby reducing the frequency and severity of sewer backups and flooding. What are the impacts of CSOs? Although CSOs may contain highly diluted sewage, they may cause temporary water quality degradation in the waterways. Contact with waterways should be avoided following the occurrence of CSOs. Why does the Chicago area have CSOs? Chicago and the older suburbs, typical of other older metropolitan areas, have a combined sewer system, in which both sanitary waste and storm water are conveyed in the same pipe. Suburbs built since 1950 have separate sanitary and storm sewer systems. Where do CSOs occur? When CSOs occur, they impact every major waterway in the Chicago area including the following: North Shore Channel, North Branch of the Chicago River, the Chicago River, South Branch of the Chicago River, the South Fork of the South Branch of the Chicago River (Bubbly Creek), the Chicago Sanitary and Ship Canal, the Calumet River, the Grand Calumet River, the Little Calumet River, the Calumet-Sag Channel, the Des Plaines River, Salt Creek and Weller Creek. Due to the heavy urbanization in the Chicago area, CSO discharge points are numerous along these waterways. The City of Evanston has 13 potential CSO locations along the North Shore Channel between Lincoln Street and Mulford Street. What is being done to reduce the occurrence of CSOs? The MWRDGC’s ongoing Tunnel and Reservoir Plan (TARP) Project was implemented to alleviate the polluting effects of CSOs and to provide relief from local flooding by providing holding capacity for 18 billion gallons of combined sewage in its tunnels and reservoirs until it can be pumped to the water reclamation plant for full treatment. Although TARP is scheduled for completion in 2015, significant benefits have already been realized. It is estimated that since the first of the tunnels went online in 1985 until 2001, more than 578 billion gallons of CSOs have been captured and conveyed to the water reclamation plants for full treatment. Since TARP went online, the waterways have seen an increase in both the fish population and number of species present; basement and street flooding have been reduced; and there are fewer floodwater discharges to Lake Michigan. To date, more than $2 billion have been spent on the project.

Why do floodwater discharges to Lake Michigan occur? During extremely heavy rainfall in the Chicagoland area, storm runoff empties into the waterways system causing the water level to rise. The water level may rise to a level sufficient to submerge the CSO outfalls, thereby reducing the rate of discharge from the outfall. This can result in basement backups and local flooding. The discharge of floodwaters to Lake Michigan occurs when the waterways reach high levels and threaten flooding of structures along the waterway and submergence of CSO outfalls. Since the initial operation of TARP in 1985, the number of times that floodwaters are discharged to Lake Michigan has been reduced. When TARP is fully complete in 2015, the number will decrease further.