What are CSOs and why are they important?
Combined sewer overflows, or CSOs, are remnants of the country's early infrastructure. In the past, communities built sewer systems to collect both stormwater runoff and sanitary sewage in the same pipe. These systems transport wastewater directly to the sewage treatment plant during dry weather. In periods of rainfall or snowmelt, however, the wastewater volume can exceed the capacity of the sewer system or treatment plant. For this reason, the systems are designed to overflow occasionally and discharge excess wastewater directly to nearby streams or rivers.
Why are CSOs a concern?
CSOs contain stormwater and untreated wastewater and can potentially carry pathogens, solids, debris, and toxic pollutants to receiving waters. This may impact public health and the environment. This is a major water pollution concern for cities with CSOs. CSOs are among the primary sources responsible for beach closings, shellfish bed closures, contamination of drinking water supplies, and other environmental and public health problems.
Are CSOs illegal?
No. If a CSO community complies with its NPDES (National Pollutant Discharge Elimination System) permit, CSO discharges during wet weather are authorized. Note that CSO discharges during dry weather conditions are prohibited.
Why is it important to address the CSO problem now?
The City of Peru has been addressing its CSO problems for many years. Early projects included major stormwater separation projects on West Main Street, Oakdale, and Parkview Heights Subdivision. We also significantly increased the capacity of the wastewater treatment plant. In 2010, the city agreed to complete a Long Term Control Plan by 2030. The plan includes separation projects, manhole and sewer lining projects, and a storage facility to temporarily hold polluted stormwater until it can be treated at the wastewater treatment plant. This plan would eliminate combined sewer overflows up to a 10-year, one-hour rain event (1.88 inches of rain). Completing this project will help improve water quality in the Wabash River.
How much is this going to cost?
The city has spent over $26 million to this point. The proposed wastewater treatment plant and storage facility are estimated to cost $121 million.
How will the sewer improvements be paid for?
Ratepayers will pay for the improvements unless state and federal funding assistance is secured. Without outside funding assistance, we expect sewer rates to almost triple over the next five years. An average resident using 3000 gallons a month can expect their wastewater bill to go from $27.37 per month to $92.37 in 2028.
How long will this proposed solution last? Will we have to fix this again in a few years?
The plan is a long-term solution; the storage facilities and treatment plant will be operational for many decades.
Will the construction displace anyone?
The construction will occur on public rights-of-way and city-owned property. Minimal displacement is anticipated.
What is the purpose of the storage facility system?
The storage system is a series of tunnels and a large (6.5 million gallon) tank designed to capture and store overflows (CSOs) from combined sewers resulting from rainfall. The overflows are stored until the rainfall is over. The captured CSO volume is conveyed to the wastewater treatment plant to remove pollutants and disinfection before discharge to the Wabash River.
