Developing Spill Risk Factors for Sewer Renewal Prioritization

The City of Los Angeles (City) is committed to renewing its entire 10,500-kilometer (6,500 miles) sewer system in 240 sewer tributary basins. By fiscal year 2014, the City will be completing the planning and renewal of 4,700 kilometers (2,950 miles) of sewers in the 100 highest priority basins that were prioritized based on Sewer Spill Overflow (SSO) analysis. The City is to strategically prioritize the 5,800 kilometers (3,550 miles) of sewers in the remaining 140 basins in order to cost-effectively identify and correct sewer deficiencies and provide a reliable sewer system and reduce SSO occurrences. This is particularly important in difficult economic times. This article explains the new prioritization approach adopted in this effort, which incorporates factors such as SSO, pipe physical characteristics, maintenance history, condition assessment, and proximity to ecological sensitive areas, into a weighted scoring system. Every sewer segment is scored and collectively calculated to evaluate the condition of the sewer basin. It is proven that the new prioritization approach provides more in-depth risk analysis of future sewer failure, not only addressing SSO issues, but also taking potential sewer deterioration into consideration.