Long Term Control Plan for Combined Sewer Overflow
October 17, 2018
The City of Quincy will begin implementing a Long Term Control Plan for Combined Sewer Overflows in the near future. The City recently received notification that the Environmental Protection Agency has accepted the City’s plan that was submitted in August of 2017.
There are 860 communities in the United States with combined sewers, which are sewers that are intended to collect both sanitary sewage and rainwater from roofs, streets and other surfaces, into a single pipe. Although combined sewers may have been originally constructed to discharge the combined sewage directly to a body of water, such as a river or sea, advances in sanitation practices have resulted in combined sewers being modified to divert the sewage to a treatment plant under normal circumstances. During rain events, the capacity of the diversion sewers may be exceeded, at which point the excess sewage is discharged directly to the body of water without any treatment. This discharge is called a “combined sewer overflow,” or “CSO” for short.
In 1994, the U.S. EPA issued the Combined Sewer Overflow Control Policy, which is the basis for the requirements in the City’s National Pollution Discharge Elimination System (NPDES) permit addressing CSOs from Quincy’s sewers. One key part of the Combined Sewer Overflow Control Policy is the development and implementation of a Long Term Control Plan (LTCP), which is a community’s plan to reduce the frequency and volume of CSOs. Quincy submitted its LTCP to the Illinois EPA in June of 2013, as required by its NPDES permit. The LTCP that was submitted indicated that the City would control CSOs by constructing a new diversion sewer along the riverfront that would collect additional flows of sewage during rain events, at an estimated cost of $59 million. That LTCP had a development and construction period of 10 years following acceptance of the LTCP.
In early 2016, the Illinois EPA had not yet accepted the LTCP that was submitted in June 2013. Acting upon the recommendation of the Utilities Committee, the City Council authorized a comprehensive review of this LTCP due to concerns about its cost effectiveness and potential impacts for citizens and other rate payers. A collaborative effort between the Quincy Department of Utilities & Engineering and the consulting engineering firm Crawford, Murphy and Tilly (Springfield, IL) produced a radically different approach to the LTCP, which was submitted to the Illinois EPA in August of 2017 as a wholesale replacement of the former LTCP. The revised LTCP relies upon improvement to the existing CSO diversion structures to divert additional flows to the sewage treatment plant and utilizes the large diameter combined sewers as temporary storage devices during smaller rain events. The revised LTCP has an estimated cost of $25.6 million and will be implemented in several phases over a 20 year period. The revised LTCP was formally accepted by the Illinois EPA on August 30, 2018.
“Implementation of the revised Long Term Control Plan will assure compliance with all CSO regulations for the next 20 years at less than half the cost of previous plans. The City is now in a great position to renew its infrastructure while maintaining very low rates,” said Jeffrey Conte, Director of Utilities and Engineering.
The revised LTCP will save the City an estimated $33 million over the original LTCP. This equates to a savings of $2,100 for each sewer customer. The rate structure that went into effect in May of 2018 was intended to fund $56 million in improvements to the City’s water supply and sewage collection & treatment systems, which included an allocation of up to $26 million for implementation of the LTCP. If the City had not revised and resubmitted the LTCP, each sewer customer would have needed to pay an additional $126 per year in sewer fees over and above the rate structure that is in effect presently. However, the present rate structure is sufficient to fund the approved LTCP.
“Utilities Director Jeffrey Conte and the Quincy City Council should be commended for their commitment to reduce the cost of this unfunded mandate by our Federal Government. Through their hard work and partnership with the EPA, Quincy now has an environmentally friendly and cost effective solution towards combined sewer overflows. This partnership saved our customers an estimated $2,100 per customer and avoided any additional rate increases,” Mayor Kyle Moore said.