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2020 Eugene Wastewater Master Plan Chapter 4: Design Criteria 30 <br />rate of 67 gal/capita/day. This flow rate is less than the 1992 rate of 73 gal/capita/day, which is an <br />expected result of low-flow fixtures and other water conservation efforts. <br />For new construction, the Envision Eugene Comprehensive Plan estimates the average number of <br />dwelling units per gross acre for low-, medium- and high-density designated areas. Those units and the <br />estimated base flow rates are shown in Table 4-2. <br />Table 4-2: Estimated Base Flow Rates for Residential Land Use <br />Type of Land Use <br />(Designation) <br />Dwelling Units <br />Per Gross Acre1 <br />Population Per <br />Gross Acre2 <br />Base Flows Per <br />Gross Acre3 <br />Base Flows <br />Per Net Acre4 <br />Low-Density Residential 4.0 9 600 750 <br />Medium-Density Residential 5 10.7 24 1,605 2,000 <br />High-Density Residential 21.5 48 3,230 4,040 <br />1 From Envision Eugene Comprehensive Plan estimates <br />2 Dwelling units x 2.24 persons/DU – 2010 census <br />3 Population x 67 gal/capita/day – 2004 EWEB Water Master Plan <br />4 Gross acres include 25% street right-of-way. Flow per net acre = 1.25 x flow per gross acre. <br />5 Includes Row Houses <br />Base Wastewater Flow Rates for Commercial and Industrial Areas <br />Commercial and industrial developments have a wide range of flow rates. This is due to the variety of <br />products, services, and intensity of site development that may occur. Without specific development <br />plans, base wastewater flow rates can be estimated on a basis of mixed development. The 1992 USSMP <br />included a detailed analysis to establish base wastewater flow rates for each of the major land use <br />categories. A thorough review of that analysis was completed, in addition to a review of current master <br />plans for EWEB and the City of Springfield, and a review of current industrial wastewater permits. It has <br />been determined that there is no basis to modify the methodology included in the 1992 plan. A copy of <br />that analysis is included in Appendix B of this document. <br />In addition to the four commercial and two industrial base flow rates included in the 1992 master plan <br />(see Table 4-3), one additional category has been established: Campus Industrial. A brief description of <br />this is included in Table 4-1. Calculation of base wastewater flow rates are described below. <br />Campus Industrial <br />An economic opportunities analysis prepared by ECONorthwest as part of the Envision Eugene process <br />found an average of about 21 persons/acre on a sample of Campus Industrial sites in Eugene (see <br />Envision Eugene Comprehensive Plan, Employment Land Supply Study, Part II, Table 25.) The study is <br />planning for 10 employees per acre on industrial sites smaller than 10 acres (Table 31) and 6 to 14 <br />employees per acres on industrial sites larger than 10 acres (Table 32). The Campus Industrial land-use <br />category could include industries that have a varying water demand, but also may have less dense <br />development than other commercial/industrial uses. Utilizing the per capita rate of 67 gallons may <br />grossly underestimate the flow rate. A more reasonable value similar to the Light-Medium Industrial rate <br />of 3,040 gallons per gross acre per day provides a factor of safety. <br />At best these flow rates are rough estimates that may be used for preliminary planning and system <br />design. They may be checked against actual water usage in existing commercial developments and