Laserfiche WebLink
2020 Eugene Wastewater Master Plan Chapter 5: Rehab of Existing Systems 38 <br />For the model to be a useful tool, continued refinement, expansion, and maintenance of the model is <br />necessary. A flow monitor only measures the flow at a discrete point, which then represents the <br />wastewater system upstream of that point. With 30 initial flow monitor locations, each of those points <br />represents many thousands of feet of pipe. Monitoring and modeling more points increases data <br />resolution so that each measured flow represents fewer, more localized upstream pipes. The next <br />milestone in model refinement is to reach flow data resolution at no larger than 50,000 feet. <br />Furthermore, by including only pipes 10 inches and greater in diameter, the initial model contained only <br />20 percent of existing wastewater pipes. As flow monitors are deployed in upstream reaches that were <br />not included in the initial model, the model is expanded by adding the associated upstream network of <br />8-inch pipes. The location of these upstream monitors is often driven by measuring the flow in micro- <br />basins to determine areas of extreme I/I for rehabilitation. <br />Map 5-C shows the layout of the model at the start of 2020. As seen on the map, there are localized <br />areas that have been filled in with all existing 8-inch pipes. The map also shows all monitoring points <br />where the model is currently calibrated. <br />The model is maintained by analyzing flow data over time. Some flow monitors are permanently <br />deployed in key locations so that the model can be re-calibrated when system changes are detected. <br />Rehabilitation Planning Process <br />The rehabilitation needs of the wastewater system far exceed the available capital resources. Prioritizing <br />projects requires integration of many factors, including an analysis of the wastewater model, review of <br />flow monitoring data, video inspection, consideration of future development, operational capacity of <br />pump stations, and available budget. These tasks are divided among the Engineering, Wastewater, <br />Maintenance, and Administration divisions of Eugene Public Works. <br />Rehabilitation projects are generally identified 18 to 24 months prior to construction. The process to <br />prioritize capital projects begins with updating the wastewater model and the ranked micro-basin list <br />with the latest flow data. Engineering, Wastewater and Maintenance divisions meet to evaluate the <br />current areas of high I/I on the ranked list. Generally, the micro-basin with the worst I/I is given the <br />highest priority. However, the evaluation also includes: <br />• What areas of the city are expected to have development that could increase flows beyond the <br />downstream capacity if I/I efforts do not take place? <br />• Are pump stations having operational difficulties due to high I/I rates upstream? <br />• What is the pipe type and age of the system under consideration? <br />• Which areas can be rehabilitated most efficiently within the budget? <br />• What system defects are causing an inordinate impact on Maintenance operations? <br />The next step is video inspection by Maintenance or a contractor in the selected micro-basin. These <br />videos and reports enable the Engineering team to scope and design the capital rehabilitation project, <br />including mains, cleanouts, laterals, and manholes. Engineering Division prepares and bids the project for <br />construction. Once construction is complete, flow monitors are deployed to measure the effectiveness <br />of the rehabilitation, and the flow monitoring data is once again used to update, expand, and refine the <br />model.