Combined Sewer Separation

What Is a Combined Sewer System?

Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. The City's combined sewer systems transport all of its wastewater to our sewage treatment plant, where it is treated and then discharged to the Fox River. During periods of heavy rainfall or snowmelt, however, the wastewater volume in the City's combined sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams, rivers, or other water bodies.

These overflows, called Combined Sewer Overflows (CSOs), contain not only stormwater but also untreated human and industrial waste, toxic materials, and debris. These types of systems are a major water pollution concern. Environmental Protection Agency's (EPA) CSO Control Policy, published April 19, 1994, is the national framework for control of CSOs. The Policy provides guidance on how communities with combined sewer systems can meet Clean Water Act goals in as flexible and cost-effective a manner as possible.

For more information on Combined Sewers, Combined Sewer Overflows and the CSO Control Policy you can visit the EPA website.

Where Are Batavia's Combined Sewers Located?

Batavia hired Trotter and Associates to complete a Wastewater Master Plan in 2008, which included locating the combined sewer area. They located 3 combined areas in the Downtown Drainage Basin, which are described: 

  • Area 1 (PDF)
    • Bounded by Illinois Avenue to the North, Houston Street to the South, Harrison Street to the West and Batavia Avenue to the East
  • Area 2 (PDF)
    • Bounded by Wilson Street to the North, Union Avenue to the South, VanNortwick to the West and Water Street to the East
  • Area 3 (PDF)
    • Bounded by Walnut Street to the North, halfway between Carlise and Morton to the South, the old railroad spur to the west and Jefferson Street to the East

What Will It Take to Separate the Sewers?

First, the City will need to collect data of the existing storm and sanitary sewers in those areas, which means locations, elevations and inverts of the pipe and manholes, inlets and catch basins. Some of this work was completed when Trotter and Associates did their Master Plan in 2008; they surveyed the combined sewer areas. The remainder of the information was collected by City Staff, starting in the winter of 2012 until consultants were hired in 2016.

After all the data has been collected it will be reviewed, analyzed and a storm sewer system designed to find a best with existing utilities. You ask, why a new storm sewer and not a sanitary sewer? Each individual property has a service that connects their building to the sanitary sewer, therefore this system will remain as the sanitary system as it is also the most cost productive solution as well.

Once a design has been engineered, a plan for funding and implementing different sections of the sewer will be put into place. Area 2 had been the area of focus as it is directly linked with the Main Street reconstruction project. In addition, after the June 2015 rain event Area 3 and other sections of Area 2 have been identified and studied too. The outfall for Area 3 was constructed in November 2016 and separation of the storm on Elm Street in Area 2 was completed in July 2016. Final engineering continues for each area, please reference those webpages for additional info.