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4. WASTEWATER CHARACTERISTICS flow rates. The studies recommended continued and additional funding to rehabilitate the respective systems to correct structural deficiencies and reduce RDII contributions. Comprehensive RDII reduction programs in both cities fulfill NPDES waste discharge permit requirements. Both cities' programs include varying degrees of flow monitoring, TV inspection, smoke testing, and manhole inspections as appropriate. Unfortunately, the programs have not been as effective in controlling excessive peak flows as estimated in the 1978 SSES study. Limited success with RDII reduction programs has also been the case for many other communities around the state and country. The inability of RDII rehabilitation programs to achieve desired targets formed the impetus for the September 2000 Wet Weather Flow Management Plan (WWFMP; CH2M HILL, 2001), which evaluated and recommended individual technologies or combinations of technologies to manage wet weather flows. The WWFMP estimated more up-to-date and realistic rates of RDII reduction that could be expected as a result of collection system rehabilitation projects. For the purposes of the WWFMP study, two groups of system rehabilitation were evaluated: (1) rehabilitation of main lines and laterals within the public right-of-way (lower lateral), and (2) rehabilitation of the same but including portions of the laterals that are outside the public right-of-way (upper lateral). The two types of rehabilitation are referred to as "public only" and "public and private." Public only includes the entire collection system within the right-of-way limits, independent of ownership. The cities of Eugene and Springfield have collected a large amount of data in the last 5 to 10 years to measure the effectiveness of their system rehabilitation programs. The data comprise flow records taken before and after implementation of rehabilitation in specific areas. These data were used for estimating the operational and economic benefits of further system rehabilitation activity. All local data from both cities represented system rehabilitation within the public rights-of-way. Neither city has performed comprehensive system rehabilitation of the private laterals outside of rights-of-way; consequently, all local data used in the WWFMP analyses represent the public-only condition. CH2M HILL performed a three-phase analysis of the data. The first phase involved a preliminary review of the raw data that resulted in a general assessment of system rehabilitation benefit. The second involved a quantitative comparison of basin-specific data. This examination reviewed pre- and post-rehabilitation RDII quantities relative to type and amount of system rehabilitation per sub-basin. Both local and other agency data were reviewed. The third phase identified performance measures to be used in later analyses of wet weather flow management strategies. Along with performance measures, the economic costs of system rehabilitation were reviewed. Rehabilitation Practices and History Most of the data used in estimating RDII reduction as a result of public-only system rehabilitation are from City of Eugene projects and monitoring. The data are relatively recent and considered appropriate as a basis for RDII reduction estimates. The City of Springfield has also performed public-only system rehabilitation, but their data are not as current and often represent unique system conditions. Post-rehabilitation monitoring was not typically performed in Springfield. Therefore, the description of rehabilitation practices in this section is based on work performed by the City of Eugene. It was assumed that RDII MWMC_4.0_REV8. DOC 4-5