Henderson Water Utility (HWU) operates a combined sewer system (CSS) with 16 permitted combined sewer overflows (CSOs), where untreated wastewater mixed with rainwater can be allowed to overflow to a waterway without treatment. Five of our overflows have been closed and are no longer active.
These CSOs are a vestige of a time when many communities in the United States first constructed sewer systems to take sanitary and stormwater flows from developed areas and discharge them directly to the nearest natural waterway. This was the most direct and least costly solution at the time. Years later, the effects of untreated wastewater on these streams became better known, as studies showed degradation of water quality and impacts on fish and wildlife. In the 1950’s, cities were required to begin treating waste flows prior to discharge with processes characterized as primary treatment, which consisted of removing trash and floatable waste from the flow.
In the 1974 Clean Water Act, the United States set a goal of having all waters of the US suitable for swimming, fishing and recreation. After about 1975, cities across the nation began improving their wastewater treatment systems to provide a higher level of treatment, called secondary treatment, which typically involved biological processes that cleaned the water of most impurities. As time has passed, requirements for treatment and the level of purity of wastewater discharges has ratcheted up, and the quality of U.S. surface waters has steadily improved. Combined sewer discharges in wet weather became the next regulatory target. Approximately 772 communities in the U.S. have combined sewer systems of varying size and scope. Large cities like Chicago and Milwaukee were required to reduce discharges first, and many constructed deep tunnel projects to capture extremely large amounts of water for pumping and treatment after rainfall ended. As of 2010, most cities with combined sewers are under court order or are in negotiations with U.S. EPA to come up with plans to reduce and control those discharges.
Henderson’s Consent Judgment
Federal and State environmental regulations now require all operators of combined sewer systems to prepare a Long-Term Control Plan (LTCP) that demonstrates mitigation of CSOs in conformance with the Federal CSO Control Policy. Henderson entered into a Consent Judgment on August 30, 2007, requiring that HWU’s Long-Term Control Plan meet the following goals:
- Ensure that CSOs, if they occur, are only the result of wet weather.
- Bring all wet weather CSO discharge points into compliance with the Clean Water Act and Kentucky Revised Statutes, KRS Chapter 224.
- Minimize the impacts of CSOs on water quality, aquatic biota, and human health.
Our LTCP was prepared using the Presumptive Approach, following the guidance provided in the Long-Term Control Plan-EZ (LTCP-EZ) Template: A Planning Tool for CSO Control in Small Communities (EPA-833-R-07-005). The template outlines LTCP requirements for communities of fewer than 75,000 residents.
The LTCP guidance documents require several discrete action plans which, taken together, are designed to implement the water quality standards found in the Clean Water Act. First among these is a series of actions referred to as the Nine Minimum Controls (NMC). These controls were first elucidated in a document published in 1995, aptly entitled Guidance for Nine Minimum Controls. Many of the NMCs were simply ongoing operation and maintenance (O&M) programs that well-run wastewater systems will have already been doing, like proper maintenance and operation of the sewer system, and maximizing storage in the piping, prior to overflows. HWU is in compliance with the NMC policy.
Other sections of the LTCP dealt with categorization of sensitive areas, characterization of the combined sewer system, public participation, and affordability. This last section is very important, as an LTCP with too high a price-tag would place an undue burden on Henderson’s poor, elderly, or fixed-income customers.
HWU’S CSO Control Plan Strategy
Since 1995 and consistent with the CSO Control Policy published in 1994, HWU has been actively engaged in sewer separation projects and other improvements to reduce CSO volumes and occurrences. HWU has developed a proactive, three-fold approach to CSO abatement:
- Separate sewers in the older developed areas to reduce the amount of stormwater entering the combined sewer system (CSS).
- Reroute flows that currently travel through the Downtown Interceptor away from the downtown area to increase capacity within the CSS and reduce the frequency of overflows.
- Make improvements to the North Wastewater Treatment Plant to increase treatment capacity, to allow us to process additional peak flows at the NWWTP.
The above figure shows the area within the CSS that has been separated. In all, HWU has separated approximately 60 percent of the land area in the original combined sewer system.
Projects In Our Plan
Sewer separation projects completed between 1995 and 2010 have included the Center & Julia separation project, the Fifth Street separation project, the Ershig project on South Green Street, as well as many others. The total costs of these projects was $ 17.3 million.
The centerpiece of the separation projects was the Downtown Sewer Separation project. A 16 block area (later expanded to 20 blocks) bounded by 4th Street, Ingram Street, Washington Street and the Ohio River was included in this project. Construction lasted from June 2010 to November 2012. This core area of Henderson was the first area platted in 1797, and included the oldest sanitary sewers in HWU’s system, installed around the turn of the 20th century. The Downtown project involved installation of totally new sanitary sewers and water lines, and renovation of the combined sewers into stormwater-only piping. The renovation of the existing combined pipes extended the life of these assets, and saved millions of dollars by not requiring excavation and replacement of these deep sewers. The final phase of the project included paving of all the disturbed areas. The total Downtown Sewer Separation project cost, including design, construction and engineering, was $14,424,000.
The Canoe Creek Interceptor project was designed to provide a conveyance system to redirect flows that traveled through the CSS and the Downtown Interceptor, to a new pumping station and force main where they will be pumped directly to the NWWTP, avoiding the CSS. Separate sanitary flow from outside the CSS and a significant portion of the downtown area were redirected to this Canoe Creek Interceptor. Overall, 77 percent of the contributing area of flow was disconnected from the CSS through separation and redirection of flows. The project was constructed in three phases, and all have now been completed. The total Canoe Creek Interceptor cost for all phases was $13,453,380.
The North Wastewater Treatment Plant (NWWTP) project is the last LTCP project in the pipeline, and is currently under construction. The project increases the peak capacity of the plant from 15 million to 25.5 million gallons per day. This will allow the North Fork pump station and the Janalee Drive pump station to send more flow to the plant, reducing the volume of combined sewer discharges to the Ohio River and Canoe Creek. The NWWTP project includes a new headworks structure, replacing the dilapidated and deteriorating existing screening systems. It also includes an ultraviolet disinfection system that will reduce chemical usage and the lingering after-effects of residual chlorine discharged to the Ohio River. See the Projects page under the “Departments > Engineering” tab for more information on the NWWTP improvements.
Our LTCP requires us to implement a comprehensive flow metering program of HWU’s active CSOs to track the effectiveness of CSO controls on reducing overflow volumes. This program is in place, and a multi-year summary of data from this monitoring is available here.
In addition, HWU has devised a web-based system that provides nearly real-time tracking of CSO discharges to the Ohio River, which is available here. This system allows boaters and other recreational users to directly access information on times when river water may be at risk of contamination, and to adjust their activities accordingly.
We provide an annual update of progress to KDOW on the LTCP projects in accordance with the Consent Judgment. The latest version of that report is available here.
Henderson submitted an amendment to our LTCP, representing a re-thinking of priorities and deleting some projects that were in the original plan. This amendment was approved by Federal and State authorities on February 7, 2014.
Lastly, Henderson will submit a request to terminate the Consent Judgment when all of our Long Term Control Plan projects have been completed.