Condition Assessment of Sanitary Sewer Lines Using Acoustic Inspection

Sanitary sewer overflows (SSOs) continue to be an issue for collection system managers, and performing additional cleaning without knowledge of the pipe condition results in a significant waste of resources. Rapid acoustic inspection technology can quickly determine the extent of blockage in a pipe and enables the user to deploy cleaning resources much more effectively. Municipal wastewater utilities struggle to effectively manage the vast underground network of pipes that handle the transportation of raw sewage through our nation's cities and towns. Capital investment needs for wastewater and stormwater collection systems are estimated at $298 billion over the next 20 years (ASCE, 2013), further squeezing operating budgets. Condition based maintenance (CBM) can assist by efficiently targeting maintenance to locations prior to an overflow or other failures. This requires cost effective/timely information to implement. A CBM program for collection system operations can substantially lower operating costs, but until recently obtaining the required assessment information was cost prohibitive. There are two key factors influencing a CBM program's viability: inspection cost, and the fraction of pipes requiring maintenance. A novel acoustic inspection technology (recently commercialized and evaluated by the EPA) is an enabling technology that allows for economical pre-cleaning assessment of sanitary sewer lines. The acoustic inspection technology is cost effective with inspections costing 1/10th the cost of CCTV inspections. In addition, based on acoustic inspection (and validated by CCTV during pilot projects) on average 50-70% of the pipes in a system do not need immediate maintenance or further detailed inspection. It's important to note that the acoustic inspection does not replace CCTV, it helps to prioritize where and when to use more expensive CCTV resources. Using acoustic inspection to prioritize cleaning operations could provide a breakthrough enhancement for moving collection systems maintenance towards efficient CBM programs. Economic analysis and productivity measurements will be presented that evaluate the effectiveness of using a preliminary inspection tool. Multiple case studies will be discussed, while also evaluating the substantial financial and operational impacts of using acoustic inspections to prioritize cleaning operations.