HOW EFFECTIVE IS COLLECTION SYSTEM REHABILITATION?
Abstract:When considering the option of utilizing collection system rehabilitation as a method to eliminate Sanitary Sewer Overflows (SSOs), a major issue that has to be determined is how effective rehabilitation is in reducing Infiltration and Inflow (I/I). Current literature offers little assistance. Past studies have proposed rehabilitation to be very effective to completely ineffective in removing infiltration and inflow (I/I). Carollo Engineers, working with the Vallejo Sanitation and Flood Control District in California, have recently completed a pilot rehabilitation program to comprehensively evaluate the effectiveness of collection system rehabilitation. The purpose of this paper is to describe the methods and results of this pilot rehabilitation program. The methods applied to this project included selecting representative test basins, monitoring the wet weather flows, rehabilitating both sewer mains and laterals, and then measuring the reduction in both peak flow and volume. Several rehabilitation techniques were utilized including conventional dig and replace, cured in place pipe, pipe bursting, and other trenchless technologies.
Rehabilitation effectiveness was calculated by applying a model to effectively normalize the pre and post monitored flows to a standard design event. The rehabilitation effectiveness calculated from this program was then utilized across the system to determine if it could be a cost competitive method compared to conveyance and storage, or conveyance and treatment. The pilot program resulted in an approximate removal of 30 percent of the I/I (on both a peak and volumetric basis). The results obtained from this pilot rehabilitation program provide new insights into the effectiveness of rehabilitation to remove I/I from a collection system. Few programs have been completed in the past that provides this type of comprehensive analysis under controlled conditions, using continuous simulation modeling. The innovative modeling and analysis, and the lessons learned from this program will help the District and others to better apply cost-effective rehabilitation techniques to support capital improvements as well asoperation and maintenance programs.
Document Type: Research Article
Publication date: January 1, 2004
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