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Western Springs, Illinois
740 Hillgrove Ave.
Western Springs, IL 60558-1409
Ph: 708-246-1800
Fx: 708-246-0284
Stormwater Management
Introduction
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The Village of Western Springs manages approximately 75 miles of sewer pipe within the Village. Approximately 54 miles of that pipe carries some sort of storm water. The Village contains four primary types of pipe.

- Sanitary  Carries no storm water
Combined  Carries storm and sanitary water
Relief  Provides relief to combine systems
Storm Carries only storm water

The community is divided into two primary sections based upon the type of sewer system each subdivision has. Older subdivisions contain combined sewer systems and are located on the north side of the community. These systems carry storm and sanitary water in a single pipe which is then sent to the Metropolitan Water Reclamation District (MWRD). During severe storm events, it is possible for these systems to take in water beyond their capacity resulting in them being "charged". During these scenarios some residents may experience back-up in their homes. 


Explanation of Types of Collection Systems
Combined Sewer System
The combined sewer system in Western Springs is located everywhere north of 47th Street. Combined sewers carry wastewater from homes and businesses, known as grey water, as well as stormwater within a single pipe.  All water within combined sewer systems leaves Western Springs and travels to the MWRD water treatment plant in Stickney, IL for treatment.  

Homes within combined sewer system areas are more likely to experience sewer back-up during storms.  Large storms will often exceed the capacity of the combined sewer and result in both grey and storm water to back-up onto the roadway or into basements.  Western Springs has constructed portions of relief sewers in these areas in an attempt to reduce these incidents. Relief sewers act as separated storm sewers during most normal rain events.  During large storm events, relief sewers act as an overflow for combined sewers in order to keep water from backing up into homes or the roadway.   
Separate Storm Sewer System
The separated storm sewer system in Western Springs is located everywhere south of 47th Street.  A separate system contains two underground pipes. The first pipe is referred to as separated sanitary sewer, which carries grey water from homes and businesses. Similarly to combined sewers, these pipes move grey water to MWRD treatment facilities for treatment.  

The second pipe is known as separated storm sewer and only carries storm water.  These pipes vary in size but are historically larger than sanitary sewer.  Storm sewers primarily discharge into nearby waterways as they contain clean water.  During large rain events, storm sewers will often reach capacity and surcharge back onto the roadway.  Stormwater roadway storage is a very common remedy for surcharging sewers.  Storing water on the roadway keeps the water in a confined area while allowing the system to drain and access water to run overland through defined pathways called overland flow routes.  The separation between sanitary and storm sewers also provides residents and business owners with protection from sewer back-up.  

100-Year Storm Events
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The term "100-year" storm event is often falsely misinterpreted for a storm that occurs once in every 100 years.  The United States Geological Survey (USGS) defines a 100-year storm as a storm that statistically has a 1% chance of occurring in any given year.  The chart to the right outlines the percent chance that 100, 50, 25, 10, 5-year storm events have of occurring in a given year.   

Rainfall data collection is a relatively new process which has only been underway since the early 1900's.  The Illinois State Water Survey has taken this data and created, Bulletin 70, a collection of rainfall frequency tables for the State of Illinois.  These tables define a 100, 50, 25, 10, 5-year, etc. storm event by the duration of a storm and the measured amount of rainfall for that storm.   Please visit the Illinois State Water Survey - Bulletin 70 web page for detailed information. 

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The following video does an excellent job of summarizing what the 100 year storm is and isn't. Practical Engineering - The 100 Year Flood Is Not What You Think It Is (Maybe)

Inflow & Infiltration (I/I)
The introduction of storm water into a separate sanitary sewer line is often due to inflow or infiltration.  Inflow is storm water that enters the wastewater system by means of rain gutters, sump pumps, or foundation drains that are illegally connected to the separate sanitary sewer. infiltration occurs when groundwater enters the waste water system seeps through cracks in pipes, joints, or drainage structures.

I/I is a problem for various reasons.  First, separate sanitary sewers are built at a capacity to hold all waste water for the area.  Introducing storm or ground water into the system will bring the sewer to capacity and potentially create backup.  Second, the MWRD treats all wastewater after it leaves Western Springs.  Introducing storm water into the system forces the MWRD to waste resources treating water that is already clean.  

As of January 1, 2015, the Village is required to televise the entire separated sanitary sewer system every 5 years.  The MWRD introduced the Elimination of Inflow & Infiltration Ordinance to municipalities in 2014.  The ordinance was included as Article 8 in the current Watershed Management Ordinance.  The purpose of the ordinance is to aid in the elimination of sanitary sewer overflows (SSOs) and basement backups.  All municipalities in Illinois are required to adopt the new ordinance. Everything south of 47th Street is separated sewer in Western Springs and it should be noted that there are no SSOs within the Village. For more information, please visit the MWRD Inflow & Infiltration page.

The Municipal Services department created a 5-year Televising Plan that splits the separated sanitary sewer system in 5 televising cycles.  In addition, staff budgeted for the inspection of the combined sewer system, which is all sewer north of 47th Street, and areas of separated storm sewer.  Please explore the 2015 Televising Report to see the results of this year's project. 


Ways to Protect Against Sewer Backup
The majority of sewer back-ups occur in the combined sewer area of Western Springs.  In most cases, homes in these areas contain gravity sewer systems.  These systems have existing sewer services below the basement or crawl space that feed into the Village combined sewer by gravity. Issues arise when there is a heavy storm event and the Village sewer reaches capacity and surcharge into the roadway.  Back-up will occur when the basement of a home is below the stormwater level in the roadway.  
 
Overhead Sewers
Overhead sewers solve the issue of sewer back-up by raising the height of your private sewer system.  If sewers surcharge into the roadway, the water level will still remain lower than the lowest drain in the overhead sewer system.  Please see the Before/After Overhead Sewer Guide to get a better visual on the level of protection this could provide.   Overhead sewers provide the highest level of protection for sewer back-ups, but installation is costly due to the large amount of plumbing work that is required.

Check Valves (Backflow Preventer)
Check valves provide protection for sewer back-up issues at a relatively lower cost.  A check valve, or backflow preventer, acts as a one-way gate for your sanitary sewer system.  The valve itself is commonly installed in the front yard of residential homes before the sewer service reaches the Village sewer main.  The valve allows water to travel to the Village main but prevents water from heading back in the opposite direction into your home.  Please see this Backflow Preventer Diagram for more information.  

Explanation of CSOs
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A combined sewer overflow (CSO) is a relief system that diverts excess flow in combined sewer systems into a waterway during storm events.  The CSO acts as a relief path for the additional flow to prevent sewer back-up and sewer surcharging.  There are 4 active CSOs in Western Springs: two discharge into Salt Creek and two discharge into Flagg Creek.  

CSO #1 and CSO #2 discharge into Salt Creek.  These CSO's travel across Ogden Avenue and through the Cook County Forest Preserve until they reach Salt Creek.  The MWRD is responsible for maintaining these CSOs with monthly inspections done by the Village.  CSO #3 and CSO #4 discharge into Flagg Creek.  These are maintained and inspected by the Village.  CSO #3 is located at 48th and Fair Elms Avenue and CSO #4 is located at 5424 Fair Elms Avenue.

The MWRD and the Illinois Environmental Agency (IEPA) require that the Village report each discharge event.  The IEPA requires that the Village retain a National Pollutant Discharge Elimination System (NPDES) permit.  Please visit the NPDES Permit page on the Village's website for information on the document itself and reports of CSO discharges.