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2020 Eugene Wastewater Master Plan Chapter 5: Rehab of Existing Systems 36 Excessive infiltration and inflow: In addition to age-related structural concerns, the older wastewater pipes are also the primary source of excessive I/I. Excessive I/I creates a series of related problems: • Treatment plant operation: High water flow rates increase plant operational costs and reduce treatment effectiveness. Given that the Oregon Department of Environmental Quality wastewater discharge permits are issued with increasing restrictions, plant efficiency becomes more critical. • Treatment plant capacity: The existing treatment plant was designed for a maximum hydraulic capacity of 277 MGD. The average dry weather flow at the plant is under 30 MGD. Since the completion of major upgrades to the plant, the maximum flow experienced at the plant has been 231 MGD. As development occurs in both Eugene and Springfield, reducing I/I is critical to maintaining flows within the design capacity of the plant. • Wastewater system capacity: As indicated above, high I/I rates at the treatment plant are an indication of higher flows throughout the piped system. Increased I/I reduces the available capacity for development and densification. These preservation needs can be addressed through a managed rehabilitation program. Map 5-A indicates the types and areas of rehabilitation that have taken place over the last 25 years, and Map 5B shows the type of current pipe materials. WASTEWATER SYSTEM REHABILITATION PROGRAM Eugene’s wastewater collection system rehabilitation program is primarily centered on the reduction of infiltration and inflow. The overall program consists of several rehabilitation methods and quality-control procedures addressing the operation, maintenance and preservation of Eugene’s wastewater system. Methods for Problem Identification • Smoke testing is the process of flooding a blocked-off segment of the wastewater collection system with inert, artificial smoke to see where it emerges. It is used to locate collection system defects, improper connections, and storm-wastewater cross connections. System-wide smoke testing was done in the mid-1970s and again in the mid-2000s. Many defects were found in both public and private wastewater lines. A large percentage of the defects were corrected; however, it was not possible to determine the I/I reduction that was accomplished due to a lack of measurable data. Smoke testing in 2018 in the Friendly Street neighborhood, which lasted most of the summer, resulted in only 6 work orders and 2 notices to correct cross connections. Also, it was difficult to determine if the defects were public or private. • Video inspection is the process of video recording the interior of a pipe using specialized equipment. It is used to observe and document pipe deficiencies (pipe cracks, offset joints, settlement or dips in the pipeline, root intrusion, protruding taps) and detect infiltration in the mains and laterals; The inspection program has been ongoing since about 1965 and is now on about a five-year cycle to inspect all pipes that are less than 24 inches in diameter. • Manhole inspection is the process of manually investigating and reporting on the features of a wastewater manhole looking for infiltration in covers, frames, cones, structures, and connecting lines. • Flow monitoring is the process of measuring the amount of water passing by a point in the wastewater system over time. It was started in 1989 and measures wastewater flow rates at key manholes throughout the system. Flow monitoring information has two key uses: it is used to