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2020 Eugene Wastewater Master Plan Chapter 5: Rehab of Existing Systems 37 calibrate the wastewater model, and it helps locate areas with rehabilitation needs based on infiltration. The most important information is obtained during heavy rainstorm events which determines the existing amount of I/I. The flow monitoring is also used to measure flow before and after rehabilitation work to measure I/I reduction. Methods for Correction and Quality Control • Inflow source correction eliminates stormwater that reaches the wastewater system through direct connections. Historically, the connections were identified by the smoke-testing program. Roof drains, area drains, foundation drains, catch basins, sump pumps, cross-connections, etc., are disconnected from the wastewater system and rerouted to the storm or street drainage system. Manhole covers are also a source of inflow. When leaking manhole covers are identified they are corrected. • Infiltration correction needs to be accomplished in both the public wastewater system and the private building service lines to reduce flows caused by infiltration. Correction of pipe defects is accomplished in several ways: reconstruction; chemical grout; sealing; slip lining; and cured-in- place pipe (CIPP) lining.. • Structural correction is accomplished by reconstruction or lining. If pipe condition, pipe size, and capacity requirements are all acceptable, then structural conditions may be improved by lining the host pipe. Structural correction and I/I reduction are planned and constructed at the same time to allow use of the most cost-effective construction methods. • Wastewater construction inspection is essential in new construction and equally important – and even more difficult – in rehab construction. The City has established construction specifications and performs comprehensive and thorough inspections. A trained engineering technician from the Engineering Division is provided to witness and document construction or rehabilitation. Special attention is paid to lateral connections, which can be a major source of infiltration. • Design and design review of proposed wastewater systems is performed by the Engineering Division to ensure compliance with design criteria and public improvement design standards. Wastewater lines are constructed in public street rights-of-way whenever possible to provide best access for wastewater maintenance. When easement construction is necessary, more consideration is given to preserving maintenance access. Allowing the installation of private wastewater systems is minimized. When private systems are allowed, the owners must agree to provide equal construction, maintenance, and I/ I control. Long, private service lines within the public right-of-way are replaced with direct access into the public system where possible. Wastewater Model Development Eugene's complex wastewater collection system has been simulated as a digital hydraulic model in DHI's Mike Urban software. This model allows Engineering to perform complex analyses on the wastewater collection system. The model was substantially completed in 2016. It was developed and is maintained by in-house staff. The initial simulated network included only pipes 10 inches in diameter and larger and associated pump stations. The model was calibrated using 30 flow monitors which recorded both wet weather and dry weather flows. This calibration means that when a historical rainstorm is simulated, the model's output closely matches the graph of the measured flow for that storm.