Dynamic Prioritized System-wide Cleaning Schedule

The City/County Utility (CCU) manages more than 2,800 kilometers of gravity sewer pipes in the City of Winston-Salem and Forsyth County. The goal of this presentation is to describe the innovative approach developed by CCU to clean their entire small diameter sewer system (46 cm and less) over a 10-year period. This presentation will focus on tools and business processes that were implemented to achieve CCU’s goal of developing a plan that balances the economic viability of a system-wide cleaning program with the risk of a catastrophic sanitary sewer overflow (SSO) in the system.At the time the cleaning program objectives were defined, CCU did not have any pipelines on recurring maintenance schedules. The majority of the cleaning performed by CCU was in reaction to customer calls and complaints. This reactive cleaning occupied almost all of the CCU’s cleaning resources. The remaining cleaning capacity was dispatched to high risk areas annually defined by CCU’s Geographic Information Systems (GIS) group. In order to develop a system-wide schedule and change the makeup of the cleaning work from reactive to proactive, it was essential for CCU to evaluate their cleaning history and SSO history in order to minimize the risk of a catastrophic failure through cleaning prioritization.CCU needed a way to prioritize and plan out pipe cleaning work, in order to evaluate their internal and external resource needs. Additionally, in order to ensure effective cleaning was performed, CCU wanted pipes to be grouped by geographic proximity. Once the manner of dispatch was developed, the system was prioritized for cleaning based on the risk of failure. The risk of each pipe was calculated by taking all applicable data sources and weighing the data in accordance with the goals of the system-wide cleaning requirement.Once a risk-based schedule was developed, it was loaded into the City’s Computerized Maintenance Management System (CMMS), Cityworks. A tool was developed for tracking the data collected as each pipe is cleaned on the new schedule. This Cleaning Optimization Tool (COTools), imports the cleaning findings collected as each pipe is cleaned. An algorithm then processes this data and makes recommendations to modify the cleaning frequencies to ensure a continuous improvement cycle for the cleaning frequency decisions. Once the data is processed, the updated schedule is imported into Cityworks for the next cleaning cycle.At present, the initial schedule has been rolled out, and COTools has been in operation for more than one full year. COTools has been used to schedule both hot-spot and system-wide cleaning work. Both internal crews and contracted crews are now issued work orders based on the cleaning schedule exported from this tool. COTools is a dynamic tool, ergo as operating conditions change or new data become available, modifications can be made to the tool to best represent current conditions.The results to date have been outstanding; CCU has cleaned more pipes than in any of the previous five fiscal years. The optimization tool, which features risk-based schedule and the positive feedback mechanisms, and the cleaning increase contributed to a 25% decrease in SSOs during the last fiscal year as compared to the previous year.