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<br /> ~ i <br /> <br /> ~ I <br /> METHODOLOGY: <br /> City of Eugene Systems Development Charges <br /> Appendix E <br /> ' Stormwater System Charge Detail <br /> 1.0 Formula <br /> The impact nalysis for the stormwater system is based on square footage of impervious surface <br /> which create an impact on the stomiwater system by land use type. Impervious surface is defined <br /> in Section 7.2 5, Eugene code, 1971 as "earth surface made impervious by development to vertical <br /> downward p netration by water". Impervious surfaces typically consist of concrete, asphalt and <br /> roofing mat vials. The impervious surface of a residential unit is usually the roof, sidewalks, <br /> driveway and any patio areas. The cost of the existing stormwater system is used as the basis for <br /> determining t e Stormwater SDC. <br /> The Stormw ter SDC is an improvement fee, as new development will require the construction of <br /> additional sy tem capacity. The per unit cost of additional capacity is based on existing system <br /> replacement alue divided by impervious surface area. The total value of the system is estimated <br /> based on the eplacement cost of the Stormwater System components which include miles of pipe <br /> and drainag channels, stormwater cleanouts, catch basins, inlets/outlets, and manholes. For <br /> current total alue (Total Replacement Cost) of the stormwater system, see Table 6, section 1. <br /> Assessable sts were calculated using the approach specified in the City Code. The city assesses <br /> up to and inc using the first 24 inches of pipe diameter and in excess of 60 inches. For pipe over <br /> 24 inches in diameter, the city pays a proportion of the cost. The non-assessable portion of <br /> stormwater ystem costs (SDC eligible costs) is based on replacement costs, minus assessable <br /> costs. Table 6 provides a detailed breakdown of the calculation and numerical supporting data of <br /> the Stormwa er SDC. Figure 6 illustrates the calculation formula of the Stormwater SDC. The <br /> Stom~water S rates per unit of capacity can be found in Appendix G in the current adopted SDC <br /> fee schedule. <br /> To determine cost per square foot of impervious surface, the non-assessable portion (SDC eligible <br /> costs) of the tormwater system cost was first divided by the total impervious acres within the city <br /> limits. The tot I impervious surface calculated for each development is assumed to contribute to the <br /> public sto ter system. The number of acres of impervious surface in each type of land use was <br /> determined u ing runoff coefficients currently employed by the city. The cost per impervious acre <br /> is estimated ased on dividing the non-assessable costs (eligible SDC Costs) by the total number <br /> of acres of im ervious surface in the city limits. The cost for a square foot of impervious surface is <br /> calculated by dividing the cost per acre of impervious surface by the number of square feet in an <br /> acre (43, 560) <br /> <br /> it <br /> I <br /> May 1, 199 City of Eugene SDC Methodology Page E-1 <br /> <br />