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Memorandum Date: March 30, 2016 To: File From: Teri Higgins, P.E. Subject: Validation of Industrial/Commercial Design Flow Rates Unlike residential flow rates, commercial and industrial flow rates have an extreme range of values depending on the industry. The table on the following page shows the highest industrial users in Eugene & Springfield which clearly indicates the wide variation in flows. An examination of multiple municipalities also indicated a wide range of design values and methodologies. Springfield, for example, has a short list of mostly commercial uses (motels, restaurants, nursing homes, etc,) and flow rates per person, bed, etc. There is essentially no guidance on industrial flows. This method of estimation assumes that one knows the exact industry that is up stream, and yet to be identified. Philomath and Albany assign values based on Land Use, similar to Eugene, but only have a couple of categories. Clean Water Services also assigns values based on Land Use, and has a more extensive list, similar to Eugene, but typically their values are significantly higher. A summary spreadsheet is included at the end of this memo. In general, flow rates for commercial and industrial flows should be based on an assumed employment density and a flow per employee, in addition to the process flow rate for the type of industry. An EWEB graph attached indicates a relatively steady trend in water consumption for industrial and commercial users over a 20 year period. The design values included in the 1992 Urban Sanitary Sewer Master Plan were established based on the 1961 Sewer Study Report prepared by CH2M Hill and utilized a per employment flow plus an estimated industry flow. Without further evidence to the contrary, the 1992 flow rates will be carried forward in the new Master Plan. In addition, 1 new category will be established to more directly correspond to land use designations (a complete description is included in the master plan): Campus Industrial: The target employment is 21 persons/acre. The Campus Industrial land use category could include industries that have a varying water demand, but also may have less dense development than other commercial/industrial uses. Utilizing the pure per capita rate of 67 gallons may grossly underestimate the flow rate. A more reasonable value similar to the Light-Medium Industrial rate of 3040 will provide a low cost factor of safety. The flow rates listed for commercial and industrial uses are for upstream master planning purposes only, when no additional information is available as to proposed developments. Always consider other factors and use the best engineering judgement when assigning flow rates. Appendix B 2020 Eugene Wastewater Master Plan Appendix B-1