Raftelis was engaged by the City of Tacoma Public Works Department (City) to conduct a cost-of-service study for wastewater, surface water, and solid waste utilities. The study involves developing user-friendly cost-of-service models for all three utilities. The project involved training City staff on the use of the models and developing a manual on the use of the models. One of the features of the models is to integrate the data from the City’s mainframe system directly into the models so the models can be easily updated. The models will also be capable of comparing actual and budgeted revenues and expenses so the City can take corrective action if needed.
The cost-of-service analysis for the solid waste utility incorporates changeover from weekly collection to bi-weekly collection and accounting for the corresponding potential reduction in revenues. Surface water analysis included credits for properties that have direct discharge, revised rates for the incorporation of the open space program, and consideration of peaking factors. Wastewater cost-of-service analysis allocations to strength are currently at 34%, 33%, 33% to flow, BOD, and SS, respectively. The analysis includes a review of the strength cost allocation parameters to ensure greater equity. All three utilities also had discounts for low-income customers, which would continue in this analysis. Dave Davis of MSW Consultants also assisted on the solid waste components of the project.
Raftelis was also contracted by Tacoma Public Utilities (TPU) to develop water demand and production forecasts. The demand forecast predicted 10 years of water demand by rate category econometric models developed in SAS based upon annual historical demand data from TPU’s water billing system, SAP, and numerous independent variables such as weather and economic indicators. The production forecast predicted 60 years of daily production values based upon decades of historical daily data including daily weather conditions. These forecasts were created to support planning activities at TPU by supplying inputs for the cost-of-service model as well as for assisting with infrastructure master planning needs.
In another study, Raftelis worked with Tacoma Public Utilities (TPU) to develop water demand and production forecasts. Utilizing rate category econometric models developed in SAS based upon annual historical demand data from TPU’s water billing system, SAP, and numerous independent variables such as weather and economic indicators, the demand forecast predicted 10 years of water demand. The production forecast predicted 60 years of daily production values based upon decades of historical daily data including daily weather conditions. These forecasts were created to support planning activities at TPU by supplying inputs for the cost-of-service model as well as for assisting with infrastructure master planning needs.
