Over the past 15 years the elimination of Infiltration/Inflow (I/I) has allowed Johnson County Waste-water (JCW) to successfully reduce excess flows from its sanitary sewer collection system during wet weather conditions.
The Kansas county spent approximately $45 million to identify and address the needed improvements to the public sector of its sewer system. While those improvements reduced I/I by approximately 30 percent, the district found that the majority of its I/I originated from private property. To address that problem JCW began an aggressive program to identify and remove sources of I/I from private property. It was one of the first programs of its kind in the country and probably the most successful yet.
The project area involved the county?s three oldest watersheds, which have piping systems about 55 years old and primarily comprised of vitrified clay pipe (VCP) and brick manholes. The project area consisted of 742.6 miles of sewer, 17,768 manholes, and approximately 51,700 buildings. It covers approximately one half of the sewer system in Johnson County. The area is primarily composed of single-family homes, commercial properties, and a small amount of light industry.
History
Prior to the Sanitary Sewer Evaluation Study (SSES) and the system improvements, JCW staff members spent the majority of their resources addressing emergency situations. Closed circuit television inspections and sewer line maintenance were not performed on a regular basis.
Many neighborhoods experienced recurring sewer backups and overflows (SSOs) during wet weather, especially during a series of intense storms in the early 1980s. That prompted the Johnson County Board of Commissioners and the JCW department to implement a program to correct the system?s capacity problems.
The goals of the program were to protect basements from sewer backups during a 10-year storm event and prevent bypassing of untreated sewage during wet weather. After conducting the SSES, the utility determined that the most cost-effective solution was to build relief lines and make needed repairs to the aging system.
In conjunction with repairs to the sewer system, I/I removal from private property was essential to achieve the 10-year storm level protection. Early studies determined that private I/I removal would be the most cost-effective means of flow reduction during wet weather. The Private I/I Removal Project consisted of 11 phases and required that every building be inspected and tested to identify sources of I/I entering the sewer system.
Private I/I Removal Project
Implementation of the private I/I removal program required careful planning. The idea of spending public funds on private property could have been a controversial issue. With the support of the Johnson County Board of Commissioners and a tremendous amount of time from the county?s Legal Department, Resolution No. 85-96 was adopted. This decree allowed JCW to use public funds to implement the private I/I removal project. A database was established to track the identification and disconnection of I/I sources on private property.
The resolution required disconnection of the following private I/I sources and provided a maximum reimbursement per source:
- Foundation drain sump pit,$800
- Directly connected storm sump pump, $800
- Directly connected combination sump pumps or pits, $1,800
- Area drains (driveway, patio, yard, window well), $2,200
- Area drains (basement entry), $850
- Downspouts, $100
- Service line cleanout, $250
Beginning in 1985, JCW began notifying property owners that an I/I source(s) had been identified on their property and that it had to be disconnected from the sanitary sewer. To date, 15,760 sources of I/I have been disconnected from private property at a cost in excess of $11 million.
The list in Table 1 indicates the average removal cost for each I/I source disconnected on private property and the total number of each source removed.
While many different methods were used to disconnect the various I/I sources, the majority required the installation of a sump pump system to pump water away from the sanitary sewer system. All sump pumps were required to discharge outside of the house or building.
The program?s biggest obstacle was to convince property owners who were not having backup problems that they needed to install a sump pump system to help someone else. This problem was addressed by educating property owners that their existing I/I connection was contributing to sewer backups in others? basements.
It was decided early on in the project that all property owners would be treated equally and that 100 percent compliance would be achieved. Since the majority of the work was completed 8 to 10 years ago, the sump pumps are reaching the end of their life expectancy. JCW has received many telephone calls recently from property owners requesting that their sump pump be replaced. JCW required the plumbing contractor to warrant the work for a period of one year; after that time, maintenance and repair became the property owner?s responsibility. JCW reinspects all I/I disconnection?s after a period of five years to ensure continued compliance and to again inform the property owner of required maintenance.
Post rehabilitation flow monitoring revealed that I/I reduction was exceeded in all 11 phases of the project.
JCW has inspected all but four properties and disconnected all but one identified I/I source in the project area. In order to ensure 100 percent compliance with the project, JCW has issued citations to property owners who have failed to disconnect an identified I/I source and issued fines totaling thousands of dollars. Recently, JCW was forced to file suit against a group of property owners that refused an initial inspection of their property and pursued the issue to the Kansas Supreme Court, where JCW prevailed. JCW intends to pursue the few remaining property owners until there is 100 percent compliance with the program.
Conclusion
The number of sewer backups into basements and the bypassing of untreated sewage into streams and creeks have been greatly reduced. Currently, JCW has a collection systems engineer, I/I planning coordinator and four inspectors that continue to investigate the sewer system in problem areas. JCW has implemented a routine maintenance program that is designed to prevent problems before they occur.
Proactive maintenance of the collections system has played a major role in the program?s success. JCW also has established a term and supply contract with a Cured-in-Place Pipe (CIPP) vendor to repair pipes as needed. JCW now is focusing on the creation of a hydraulic model of the entire system that will be useful in evaluating problem areas.
JCW also has continued to address problems on private property. Following a 150-year storm event on Oct. 4, 1998, JCW implemented a backup prevention program that provides funding for the installation of a backwater valve or plumbing modification to prevent future sewer backups.
The completion of the private I/I removal program has been instrumental in the successes JCW has achieved over the past 15 years. Johnson County will continue its efforts until all wet weather related sewer backups and sanitary sewer overflows are eliminated.
About the Author:
Ron Thomann is Planning Coordinator for the Infiltration.Inflow Removal program at Johnson County Wastewater. For more information, contact Thoman at 913-681-3200, extension 2104 or e@mail at [email protected].