Alternate: Application of a Risk-Based Asset Management Framework for the Des Moines Stormwater Master Plan

The City of Des Moines, Iowa (the City) awarded a contract to CDM Smith for development of a comprehensive city-wide stormwater master plan (SMP). This session will communicate the value of applying a risk-based asset management framework to the City's SMP development. Municipalities will benefit from this discussion by learning about risk-based asset management principles for stormwater systems. This framework is adaptable, eases prioritization efforts, and enhances communication with stakeholders. The SMP was developed to provide a systematic, prioritized, and proactive framework for addressing the City's stormwater management challenges. To date, the SMP has consisted of two phases with the first focusing on a needs assessment and programmatic framework, and the second phase began implementation of the city-wide risk analysis and the more detailed application in the initially selected watersheds. The needs assessment and programmatic framework phase (Phase 1) was conducted by completion of a program audit, review of best practices, and identification of new practices to enhance the City's stormwater management program, including the initial development of a risk-based asset management framework. During the subsequent implementation phase (Phase 2), processes identified during the initial needs assessment were applied to characterize the existing stormwater system and provided insight for short- and long-term financial planning. Overall, the SMP informs future strategies by providing actionable recommendations and processes to manage assets more efficiently. Continued evaluation of level of service objectives, public engagement, and process refinement bring life to the SMP, allowing for future application and adaptation by the City. During Phase 1, a risk-based asset management framework was developed to prioritize stormwater asset inspections, maintenance, renewal, and capital projects. Under this structure, the Likelihood of Failure (LoF) and Consequence of Failure (CoF) are used to calculate the Risk associated with each asset. Each of these parameters ' LoF, CoF, and Risk ' range in value from 1 to 5, with 5 being the worst. LoF is based on the assessment of an asset's condition and performance, while CoF is based on an asset's significance to the stormwater system and the impact severity of failure. Condition may be evaluated through field investigations or estimated using a surrogate parameter easily obtained through analysis of asset properties, such as age and material. The preliminary LoF based on surrogate parameters may be used in conjunction with CoF to determine an initial Risk score and inform inspection priorities. This assessment allows itself to be conducted with limited field investigations to provide an initial estimate of system risk and needs. Initial estimates of system risk may then be used to identify priority catchments for detailed investigation and recommended capital improvement projects (CIPs). Specific processes for this purpose were developed as part of Phase 1. Phase 2 of the SMP applied the processes identified during Phase 1 to the City's stormwater system. A desktop analysis was performed to determine the LoF, CoF, and resulting Risk score of each asset. Surrogate parameters were used to determine LoF, because inspection data was not widely available. GIS-based algorithms were developed to calculate these LoF, CoF, and Risk scores for each asset. From this, three priority catchments were identified in the City. Upon review of priority catchments with City stakeholders, the project team deployed for field investigations to fill data gaps and determine a more accurate LoF condition score. Investigations included pole camera and CCTV of pipes and adjoining structures and visual inspections of stormwater basins. Parallel to field investigations, SWMM models were created for the priority catchments. Inspection-based LoF condition scores and LoF performance scores from the SWMM models were used to identify assets that should be included in a capital improvement project (CIP) due to the need for renewal, either by rehabilitation (lining) or replacement. Conveyance improvements and opportunities for additional storage were modeled to provide a preliminary CIP approach. Results of the desktop analysis used to inform priority catchment selection were also used to identify potential CIPs in non-priority areas. These projects were identified by focusing in areas with the highest LoF and Risk scores. Although these CIPs require additional design, the preliminary analyses results in short-term financial planning data. The necessity and reach of these identified CIP locations will be confirmed through final field investigation and detailed design. In additional to the risk-based asset management framework and identification of potential CIPs, other key outcomes of the SMP included: - Development of level of service (LOS) objectives - Development of a public outreach plan - Development of white papers regarding policy development to support the asset management framework - A summary of recommended operation and maintenance activities per asset type - Creation of Lucity-based asset management dashboards, improved asset inventory, inspection forms, and other tracking resources, as well as staff education on use of Lucity resources - Development of an Excel-based tool to estimate asset inspection and renewal needs based on surrogate parameters of age and material for use in long-term planning - A strategy for implementing SMP recommendations and processes, including identification of staffing needs - Short- and long-term financial planning recommendations Final deliverables of the Phase 2 Des Moines SMP are currently under review and will be finalized in early 2023. As the City implements SMP recommendations, the assessment methodology, data collection approach, and other processes may be refined to better support the City's system. Efforts should focus on ramping up proactive inspections to help shift asset management from reactive to proactive, further developing the asset inventory and understanding of the system's current condition. Moving forward, the developed risk-based asset management framework provides a clear path for asset evaluation and CIP prioritization, while providing flexibility for future iterations.