Rain and wastewater mixing together is a costly problem for countless municipalities with aging sewer systems. As rain leaks into water filtration systems, there is added strain to the sewer systems and municipal operating costs rise. North Kansas City, MO, has teamed up with Insituform Technologies, Inc., to rehabilitate its sewer system and successfully fight the problem.

North Kansas City's 2001 annual report offered evidence of the resulting cost savings from this initiative. The report states that during the last four years, while Insituform has been rehabilitating the municipal sewer pipes, there has been a decrease of approximately 1.1 million gallons of water going through wastewater treatment daily. Since North Kansas City pays 88 cents per hundred cubic feet of water in treatment costs, that decrease translates to approximately $1,294 per day, $38,820 per month (based on a 30-day month), or $472,310 per year in savings for the municipality.

"Rehabilitating our sewer system was vital to our community," said Randy Casey, North Kansas City superintendent of utilities, who is responsible for water, sanitary sewer and storm sewer services. Casey said he was very pleased to see the big decrease in the amount of water that was pumped for treatment as Insituform's rehabilitation work progressed.

Founded in 1833 and incorporated in 1912, North Kansas City is a well-planned community that had homes, paved and lighted streets, a waterworks system and parks in advance of its inhabitants. Although North Kansas City currently has a residential population of less than 5,000 people, it is home for more than 1,000 companies engaged in manufacturing, warehousing, transportation, wholesale and retail trade, and business and personal services.

Aging concrete sewer pipes, ranging from 8 inches to 36 inches in diameter, had begun to create inflow and infiltration problems. As sewers age, they deteriorate in many ways. Cracks appear and joints separate. Infiltration through these cracks and joints creates external voids and accelerates structural deterioration that can overload collection systems and treatment plants.

In 1992, North Kansas City chose Insituform Technologies to begin the sewer rehabilitation process using its "trenchless technology." Instead of digging or excavating, Insituform uses a "cured-in-place" method that restores the structural integrity of deteriorated sewers. A felt tube is manufactured to fit inside the existing sewer. The tube is soaked in polyester resin, which is liquid when cooled. Later, workers feed the resin-filled tube into the existing sewer pipe from a manhole, using water pressure to push it inside the sewer. Once the liner is in place, the water circulating through the pipe is heated to harden and cure the resin, producing a hard, dense pipe. This new "pipe-within-a-pipe" has a life span comparable to that of a new sewer. With this process, Insituform offered the least disruptive solution to present and potential problems.

Wastewater and treatment services in North Kansas City are contracted through its metropolitan neighbor Kansas City, MO. The municipal managers knew that leakage into the sewer system were adding to the amount of water pumped for treatment. When the sewer rehabilitation began, North Kansas City pumped approximately 4.6 million gallons of daily (mgd) water. On a rainy day, however, there could be spikes of between 8 and 12 million gallons of water pumped daily.

In 1997, North Kansas City began to regularly measure the amount of rainfall received monthly and the average mgd flow. As the work on its sewer collection system continued, North Kansas City continued monitoring how much water flowed through the system and rainfall amounts. In the figures released in its October 2001 annual report, North Kansas City announced the results. The average of 4.6 mgd in 1997 had been reduced to 3.5 mgd, or by 1.1. mgd.

The rainfall, it seemed, was having less and less impact on the amount of water treated, even during very rainy months. In July 2000, for instance, North Kansas City received 8.32 inches of rain, as compared to only 3.62 inches of rain in July 1997, but it still reduced the amount of water pumped to Kansas City.

Additional cost savings resulted from Insituform blocking off of obsolete pipes that should not be connected to the system, Casey reported.

Insituform has rehabilitated approximately 50% of North Kansas City's 30 miles of sanitary sewer lines since 1992. Casey estimates that if water levels had been closely monitored and measured since the project began, the drop in water which was pumped for treatment might be as much as two million gallons of water daily.