DuPage and Cook Counties Hinsdale, Illinois
Flagg Creek originates in DuPage County in the Village of Clarendon Hills, then flows eastward underground in a pipe through the Village of Hinsdale until it surfaces near Veeck Park. It then flows approximately nine miles in a southerly direction before discharging to the Des Plaines River just downstream of Willow Springs. Its 18 square mile watershed receives runoff from suburban Cook and DuPage counties.
In 2007, the Village of Hinsdale renewed their five-year National Pollutant Discharge Elimination System (NPDES) permit for their combined sewer overflows (CSO). This permit included a new CSO with an excess flow storage and treatment facility (facility or storage facility) to be built in Veeck Park which is adjacent to Flagg Creek. Veeck Park is located in Cook County near where 47th Street crosses Interstate 294. Construction has started on the excess flow storage and treatment facility.
An excess flow storage facility is able to hold sewage and stormwater when rainfall events exceed the capacity of the wastewater collection and treatment system. The storage facility will hold the wastewater until the treatment system can process it. If the flow exceeds the storage capacity, then the wastewater will be discharged to a local creek. At this storage facility, any discharge to Flagg Creek will be screened, disinfected with sodium hypochlorite and stored in the one million gallon underground storage tank prior to discharge.
A combined sewer overflow system has one pipe for managing both sewage (municipal wastewater) and stormwater. Under normal circumstances, the wastewater treatment facility can handle these combined flows. However, when rainfall events exceed or overwhelm the ability of the system to handle the volume, excess flow is discharged into local creeks. The discharge of this excess flow is necessary to minimize sewer backup into homes.
The Veeck Park storage and treatment facility is under construction and will be operational later in 2009.
This CSO will only discharge if the sewer system and storage tank capacity is exceeded. Much of the chlorine in the sodium hypochlorite will be used up in the disinfection process. There will be little excess chlorine beyond what is needed for disinfection. Any remaining chlorine is not expected to persist in the creek. A rainfall event will also increase the amount of water in Flagg Creek such that any discharge from the CSO will be greatly diluted by the water already in the creek. Therefore, there will be no impact on the aquatic life.
CSOs are legal under the federal Clean Water Act. The Village of Hinsdale has an NPDES permit for CSOs that was reissued on April 9, 2007, and became effective on July 1, 2007.
The Village of Hinsdale NPDES permit currently lists four CSOs plus the treated combined sewage outfall at Veeck Park currently under construction. Flagg Creek is the receiving stream for all of these CSOs.
The Flagg Creek Water Reclamation District (District) discharges treated municipal and industrial wastewater from the communities of Hinsdale, Clarendon Hills, Oakbrook Terrace, Oakbrook, Westmont, Burr Ridge, Willowbrook, Villa Park, Lombard and Elmhurst to Flagg Creek. The District NPDES permit includes one treated combined sewage outfall. The Village of Western Springs NPDES permit also includes two CSOs that discharge to Flagg Creek.
Discharges occur when the capacity of the treatment and collection system is exceeded by rainfall events. During 2008, the Village of Hinsdale reported five CSO discharges. The goal is to minimize CSO discharges to less than four per year.
The village has undertaken this project to address previous violations of the federal Clean Water Act. In order to minimize the impact of untreated discharges, flow volume monitoring and modeling was completed by Hinsdale. Based on the results of the study, the Village of Hinsdale determined that a treated excess flow facility should be installed at Veeck Park. Some of the untreated flows, which previously were directly discharged to the creek, would now be screened, disinfected and stored in the one million gallon underground tank. As the volume of water in the collection system decreases, the flow from the tank would be conveyed south through the sewer system to the Flagg Creek Water Reclamation District treatment facility for further treatment. Combined sewer overflows at this facility would only occur when the tank exceeded capacity. Please keep in mind that any excess flow discharges from the tank to Flagg Creek will now be screened and disinfected.
The village owned the property necessary for locating the one million gallon underground storage facility, the site is at a low elevation relative to the wastewater collection system and is close to Flagg Creek. This site is a former wastewater treatment facility.
No. The Agency is not providing grants or loans for this facility.
Better water quality will benefit the aquatic life in Flagg Creek. Currently, all of the Hinsdale CSOs are discharging untreated wastewater to Flagg Creek. Any discharges from the new facility will be screened for solids and disinfected. The excess flow storage facility can store one million gallons of wastewater. This will give the Flagg Creek Water Reclamation District additional time to collect and treat wastewater during rainfall events. Any wastewater stored in the underground tank can then be piped to the sewage treatment plant for further treatment.
No. The amount of water in the creek will be similar to existing conditions. Less water will actually enter Flagg Creek in the vicinity of Veeck Park since the new facility will hold one million gallons. If the excess flow to the collection system is less than one million gallons, this CSO will not discharge to Flagg Creek. If this storage tank were not built, then all of the untreated CSOs and stormwater would be discharged to Flagg Creek.
Any discharge from a Hinsdale CSO must be reported on the monthly discharge monitoring report (DMR) which the Village of Hinsdale is required to submit to the Agency as regulated by the NPDES permit.
The Village of Hinsdale is required by its NPDES permit to develop a Long Term Control Plan for assuring that the discharges from the CSOs (treated and untreated) do not cause or contribute to violations of water quality standards or cause use impairment in the receiving stream.
included the plan to build the Veeck Park facility?
Yes. The NPDES permit was public noticed for 30 days beginning February 28, 2007. The Village of Hinsdale posted the public notice at its offices. NPDES permit public notices are also available on our Agency website at www.epa.state.il.us.
for the Veeck Park wet weather treatment-storage facility?
No. The Agency is not required to public notice construction permits. The concept of the excess flow treatment facility was approved in the NPDES permit of July 1, 2007. However, the construction of this facility could not commence until the Illinois EPA approved the actual engineered construction plans. A construction permit application for the project was submitted to the Illinois EPA on October 8, 2008. Based on our review, the design complied with the regulations and a construction permit was issued on January 20, 2009. The Village of Hinsdale also conducted a special community meeting, two planning commission meetings and two public hearings regarding the proposed facility. Village board meetings and public hearings are public noticed in the Doings Newspaper and in the Hinsdalean the week before any given meeting. The treatment tank will not eliminate all overflows, but will be part of Hinsdale’s Long Term Control Plan to assure that any discharges comply with water quality standards.