Stormwater Permit Renewal Update

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~~.. + _ - 6.2.1 Permit Area The updated annual pollutant load estimates are based on the estimated permit area at the end of the third permit cycle (i.e. 2013). An assumption was made that future development will occur at similar rates as compared to actual development trends from the year 2000 to 2008. This approach identified the future, five-year development demand for vacant parcels by land use category, and assumes development will occur within the Eugene City limits either as an existing vacant parcel currently located within the city limits or as an existing vacant parcel located outside city limits but inside the Eugene urban growth boundary which would be annexed to the city limits upon development. The area within the Eugene city limits as of 2008 is 27,763 acres, and based upon actual development trends from 2000 to 2008, the projected area within Eugene city limits by 2013 will be approximately 28,220 acres (an increase of 457 acres or 1.6%). , 6.2.2 Land Use Existing City of Eugene Land Use descriptions were generalized into six categories corresponding to those for which land use pollutant concentration and impervious information either specifically existed or could be approximated using another representative land use category, as follows: Residential (Single Family); Commercial; Multi-family Residential; Open Space; Industrial; and Vacant. The updated annual pollutant load estimates assume that current land use information is still accurate for currently developed parcels and that the future development will occur in accordance with Eugene-Springfield Metropolitan Plan land use designations. The projected permit area acres by generalized land use category are provided in Table 6-1. Table 6-1. City Limits Area Projected to 2013 by Generalized Land Use Category Total Projected Pro'ected Area b Generalized Land Use Cate ories acres , 2013 Area, 2013 Multi- (acres) Residential Commercial family ~ ace P Industrial Vacant Residential 28,220 13,205 5,108 1,446 4,712 1,739 2,011 6.2.3 Impervious Surface Area Factors Effective impervious percentages for select land use categories were taken from the City's Stormwater Basin Master Planl l, and adjusted to incorporate non- tax-lotted streets and rights- of-way into each generalized land use category. Table 7-5 shows the associated impervious values used for modeled land use types. The impervious surface percentages are then used to calculate the runoff coefficient for use in generating the update pollutant loads. t t See City of Eugene Stormwater Basin Master Plans (2002), Appendix B. 10-82