Resolution No. 4793 - Laserfiche WebLink

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MWMC FACILmES PLAN reduction conclusions developed using City of Eugene data would also apply to the Springfield system. The City of Eugene has foc~ased its wastewater rehabilitation efforts on sUb-basins with high wet weather to dry weather flow ratios. The City has extensive video inspection data showing collection system defects. These data have been evaluated by staff who have assigned deficiency ratings to pipe reaches. These deficiency ra~-~gs, along with flow monitoring, have been the basis for prioritizing and implementing City of Eugene public- only system rehabilitation. The majority of the lines rehabilitated to date were 8 inches in diameter. For the most part, the main line was 5 to 10 feet deep and the average depth of the service lines was about 4 feet deep at the edge of the right-of-way. Eugene's comprehensive public system rehabilitation approacA includes rehabilitating the majority of the main line, building services and connections, and manholes with_in the right- of-way. City staff have most often selected trenchless liner as the rehabilitation method. Replacing building service cormections at the main and sections of service lines located within the public fight-of-way has also been a major component of the City's rehabilitation effort. For building service lines within the public right-of-way, the City has installed, through open excavation, new PVC pipe with rubber-gasketed joints and taps at the main line. An additional component of the rehabilitation program involves mod/b/Lng manholes to reduce the surface inflow potential, and sealing the interior barrel sections and bases (where needed) with internal cement-based material to reduce or elLminate iruCiltration. In a few cases, the City performed, a spot repair on a segment of pipe instead of lifting the whole pipe. For these cases, the whole segment and its associated length were cour~ted as being rehabilitated. With regard to RDII reductions attributable to system rehabilitation, Eugene-Springfield's experience was compared with that of other agencies within and outside of Oregon. As in Eugene and Springfield, monitoring data from other agencies were ~j/3ically obtained within a few years of completing system rehabilitation projects, so the data were not necessarily representative of RDII reduction over the long-term. Data representing RDII reduction over the long-term were not identified. In general, agencies were found to address system rehabilitation in one of three ways: 1. Rehabilitation of main lines only (no portion of the lateral). 2. Rehabilitation of main lines and lower laterals (that portion of the lateral in the public right-of-way). 3. Rehabilitation of main lines as well as upper and lower laterals (the entire lateral, both in the public right-of-way and on private property to the struch~e served). Hydraulic Modeling A hydraulic model was developed to depict existing and future flows in the wastewater collection system, and the expected RDII reduction benefits in the system for both public- only and public and private rehabilitation efforts based on the estimated RDII reductions attributable to system rehabilitation. MW~C_40_REV8 DOC