Independent Evaluation of Sewer Repair Techniques For the Upper Waller Creek Basin Rehabilitation Project: Material Assessment

This thesis summarizes a study to evaluate the overall effectiveness of three proprietary methods of "trenchless" spot repair of wastewater pipe for the City of Austin, Texas. The objective of that portion of the study encompassed in this report is to evaluate and compare, through field observation and laboratory testing, the structural integrity and watertightness of the repair processes. All of the repair methods were fieldd demonstrated in Austin, Texas on 8-inch unreinforced concrete wastewater pipelines. Two of the methods investigated are in-line epoxy resin repair techniques: one method employs a robot to prepare substrate surfaces and to inject epoxy into pipe defects; the other method of epoxy repair employs an inflatable rubber bladder to form a continuous epoxy collar at the defect. The third method, a joint effort between the City of Austin and a pipeline rehabilitation company, achieves its repair from the exterior of the pipe: a vacuum excavator is employed to provide small-hole access to the pipe for subsequent placement of a cement grout collar around the pipe defect. The testing regimen investigates repair material properties and repaired pipe performance. Test specimens were obtained by excavation of actual damaged pipe repaired by the epoxy injection techniques. Standard property tests of the epoxy repair materials showed that the two epoxies differ significantly in strengths and behavior; relative advantages and disadvantages are discussed. Tests of the repaired pipe specimens yield results for bond strengths and watertightness of the repair, which also differ significantly between the repair methods. Recommendations are made for improved effectiveness of repair.Waller Creek Working Grou