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The County of DuPage
Wheaton, Illinois

Stormwater Frequent Asked Questions (FAQ's)

During any significant rain event, localized flooding may occur.  With these events come a lot of questions and misconceptions about why some areas flood, and who is responsible for the flooding.  This fact sheet clarifies many of the misconceptions associated with the County's Stormwater Management Department and their role during an event.

Misconception:  SWM is responsible for any flooding that happens anywhere within the County.


  • SWM is responsible for regional overbank flooding, not localized drainage and flooding issues.
  • Incorporated municipalities maintain their own storm sewer systems and are responsible for any overland flooding that may occur as a result of local drainage complications.
  • SWM coordinates operations of stormwater facilities with impacted municipalities to assist them in their own flood control operations.  
  • In unincorporated DuPage County, the Public Works Division is responsible for responding to and mitigating of local flooding and drainage issues. 

Misconception:  SWM doesn't operate stormwater facilities soon enough during a significant rain event.


  • Facilities are operated as outlined in each facility's operating plan. 
  • Operation of these facilities has been determined through computer modeling of different storm events to provide the optimum beneficial plan for each facility.  This modeling takes into account existing stream elevations, hydrology and storm forecasts to optimize the usage and capacity of the facility.
  • Cameras are available for remote monitoring of operations at Fawell Dam, Elmhurst Quarry and Wood Dale Itasca Flood Control Reservoir. 

Misconception:  SWM is not working to solve regional flooding issues in the County.


  • SWM develops and updates watershed plans to help alleviate regional flooding occurrences and impacts throughout the entire County. 
  • This process includes engineering studies that model storm scenarios and makes recommendations on projects that could reduce the impact of flood events. 

Misconception:  When the County took over the Fawell Dam they raised the height of the dam and changed its operating plan causing flooding in upstream communities, like Warrenville and Carol Stream.


  • The only changes made to the dam were to bring the structure into compliance with modern dam safety regulations. 
  • The height of the dam was lowered by three ft and the top was armored to create an emergency spillway. 
  • The flank levee protecting the Cress Creek area of Naperville was raised and extended.  The flank levee does not impact downstream flowing water, rather it keeps water stored behind the dam from spilling sideways into the area.
  • These changes made Fawell Dam safer for upstream communities from rain events larger than the original design for the facility.  Fawell Dam is in compliance with current dam safety regulations.

Misconception:  The operation of the Fawell Dam causes flooding in upstream communities, including Warrenville and Carol Stream.


  • Operation of the Fawell Dam stores floodwaters upstream of the dam in the McDowell Grove Forest Preserve.
  • The Dam is operated in conjunction with the procedures outlined in the operating plan and this operation does not cause flooding within Warrenville, Carol Stream or any other upstream community.
  • The County utilizes the original plan designed by the State and verified by the County at the time we took over the facility.

Misconception:  The operation of Fawell Dam is destroying the McDowell Grove Forest Preserve. 


  • This Forest Preserve property was originally purchased by the State in order to provide storage of flood waters. 
  • The property only later was turned into Forest Preserve property to provide an additional use during dry weather. 
  • Floodwater is not stored in the upstream pool long enough to adversely affect the flora of the preserve.

Misconception:  The County lowers the gates at the Fawell Dam, and then does not raise them.


  • The County lowers and raises the gates at Fawell Dam as a function of stream elevations. 
  • Gages are upstream, downstream and at the Dam to monitor elevations, and these elevations determine the operation of the facility as outlined in the operating plan.
  • Cameras with real-time images are available on our website, to see the operation of the gates.

Misconception:  The County is not opening the Wood Dale - Itasca Flood Control Facility soon enough to prevent flooding.


  • Wood Dale Itasca Reservoir is designed to minimize the peak flow of water moving downstream on the mainstem of Salt Creek to prevent flood damages.
  • Proper gate operating positions are determined by engineers using various inputs including downstream and upstream river elevations, rainfall totals, projected rainfall totals and results from our Salt Creek flood forecasting computer model.
  • Operation of the gates varies for each event, but they are always operated to provide the maximum flood height reduction downstream.
  • No gate operations occur unless the downstream river elevation at Irving Park Road reaches 676.00.  The County maintains a river level sensing station at Irving Park Road for this purpose.
  • Camera images of the river gage can be viewed on the County's flood operations web page at

Misconception:  People's houses are flooding and the Elmhurst Quarry is not full or taking in enough water to prevent the flooding.


  • The County operates the Elmhurst Quarry in conjunction with the facility operating plan to mitigate overbank flooding from Salt Creek.
  • The 7 ft by 7 ft sluice gated weir is opened based on flood levels reaching a trigger elevation at Harger Road in Oak Brook.  The sluice gate allows the Elmhurst Quarry to take in water at a lower stage than the fixed weir.
  • Additional water is diverted into the Quarry when water levels overtop the fixed weir and flow into the Quarry along with the water diverted from the sluice gate.
  • Until Salt Creek tops the fixed weir, no more water can possibly be diverted than is allowed through the fully opened sluice gate. 

Misconception:  The Spring Creek Reservoir fills up too quickly and doesn't provide any flood relief.


  • The facility is a limited capacity reservoir and fills up quickly during storm events. 
  • The reservoir was designed to provide flood relief up to a 4 percent chance of occurring in any one year storm (commonly referred to as the 25-yr return period storm). 
  • Storms with greater than a 25-yr return period will fill the facility before the flood peak passes along Springbrook Creek.  There is simply not enough capacity at the facility to provide protection in these larger events. 
  • This reservoir is operated in conjunction with our Meacham Grove gravity in - gravity out reservoir located in the Meacham Grove Forest Preserve.  Together they provide flood relief for Roselle, Bloomingdale and Itasca.
  • When elevations reach safe levels, the reservoir is pumped back into the Creek to make room for storage for the next storm event. 

It is important to note that local and regional flood control facilities cannot stop all flooding, especially when a hundred year event occurs.  When these events occur, the infrastructure in place cannot handle the sudden rush of water that occurs. Therefore, it is important for homeowners to ensure they are taking the necessary steps to protect their property from the dangers of flooding.

Prepare your house.

  • First make sure your sump pump is working and then install a battery-operated backup, in case of a power failure. Installing a water alarm will also let you know if water is accumulating in your basement.
  • Clear debris from gutters and downspouts.
  • Anchor any fuel tanks.
  • Raise your electrical components (switches, sockets, circuit breakers, and wiring) at least 12 inches above your home's projected flood elevation.
  • Place the furnace, water heater, washer, and dryer on cement blocks at least 12 inches above the projected flood elevation.
  • Move furniture, valuables, and important documents to a safe place.

Safeguard your possessions. Create a personal "flood file" containing information about all your possessions and keep it in a secure place, such as a safe deposit box or waterproof container. This file should have:

  • A copy of your insurance policies with your agent's contact information.
  • A room-by-room inventory of your possessions, including receipts, photos, and videos.
  • Copies of all other critical documents, including finance records or receipts of major purchases.