UNIQUE PERFORMANCE-BASED I/I REDUCTION CONTRACT EXCEEDS GOAL
Abstract:As part of the Overflow Abatement Program for Nashville (Tennessee) Metro Water Services (Metro), work under a unique performance-based contract for infiltration/inflow (I/I) reduction significantly exceeded the goals for the project. The design-build team of ARCADIS U.S., Inc. and Reynolds Inliner, Inc. successfully completed the five-year “find and fix” sewer rehabilitation contract in late 2005 and achieved a 41 percent reduction in total I/I from the Whites Creek basin. Due to the documented results, Metro awarded a monetary bonus for exceeding the performance guarantee. The paper will describe the unique contractual arrangement, the performance requirements, the methodologies for successful I/I reduction, and the final documented results of the five-year project.
Under the 5-year contract, which began in late 2000, the team was responsible for determining the most cost-effective rehabilitation program for the Whites Creek sewer basin, which covers some 20,000 acres. The contract stipulated either a 500,000 bonus for documenting a 30 percent reduction in I/I or a 500,000 penalty for failure to achieve a minimum reduction of 20 percent.
When the final rehabilitation was completed, the team had completed over 94,000 linear feet (LF) of cured-in-place pipe (CIPP) relining from 8-inch to 24-inch, rehabilitation of 415 manholes, renewal of over 860 service laterals, and cleaning and televising over 250,000 LF of sewer lines. The final construction cost for all rehabilitation work was approximately 6.8 million, within Metro's budget.
Following completion of the find-and-fix rehabilitation efforts, Metro analyzed flow monitoring data to document the effectiveness of the find-and-fix rehabilitation program. They confirmed that I/I volume had been reduced by 41 percent – well over the guaranteed reduction. As a result, Metro awarded the bonus to the team. In addition, Metro documented that the peak hour I/I had been reduced by 42 percent, over 400 million gallons of annualized I/I had been eliminated, and overflows from the Whites Creek pumping station had been reduced by approximately 75 percent.
The Whites Creek I/I Reduction Contract was recognized by Trenchless Technology magazine as the 2006 Rehabilitation Project of the Year. In addition, the project was awarded the 2006 Honor Award for Engineering Excellence for water and wastewater projects in Tennessee by the American Council of Engineering Companies.
Document Type: Research Article
Publication date: 2007-01-01
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