Indian Bend Wash Side Inlet Pipe Assessment Using the NASSCO Pipe Certification Assessment Guidelines

The Indian Bend Wash is a drainage channel in Scottsdale and Tempe that provides flood protection for residents and businesses. As the wash approaches the Salt River (Tempe Town Lake), levees provide protection from the higher flows that would typically flow out of the banks in this area. The levee design incorporates pipelines, or side inlets, to safely convey impounded storm flows on the landward side of the embankment into the wash. These side inlets pose a potential threat to the structural integrity of the levees. The U.S. Army Corps of Engineers (Corps) periodically inspects structures in the rehabilitation program (RP) to ensure continued flooding protection. A periodic inspection report (PIR) is created to document the results of the inspection. Project Engineering Consultants, Ltd., (PEC) provided a condition assessment of twelve side inlet pipes in the City of Tempe (Tempe) portion of the levee system under the direction of Tempe and the Flood Control District of Maricopa County (FCDMC). The Corps recently adopted the National Association of Sewer Service Companies (NASSCO) standard for assessment of pipes and culverts that penetrate the levees. PEC relied on the NASSCO Pipe Assessment Certification Program (PACP) to provide the side inlet pipe assessment. The PACP assessment, the first to be implemented on these levee pipes, identified potential issues and provides a baseline condition rating for the side inlet pipes. Using this baseline, future assessments will indicate the rate of change in pipe deterioration and estimate the remaining useful life of the facility. This paper presents several aspects of the NASSCO PACP procedures for the levee side inlet assessment. The discussion will include methods employed to overcome the challenges not typical in sanitary or storm sewer systems during pipeline assessments. The pipeline assessment produces large amounts of data during the inspection and assessment process, which categorizes and summarizes the data for ease of use. This data includes information that helps develop structural, operational, and maintenance defect ratings for each segment of the side inlet. The narrative discusses the ratings and other observations, including the interpretation and summary of the assessment results. An organized reporting table was also developed to succinctly present the results of the assessment to the agencies for a response to the inspection findings noted in the PIR.