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I* fY <br /> METHODOLOGIES: <br /> ,City of Eugene Systems Development Charges <br /> Appendix E <br /> Stormwater System Charge Detail <br /> 1.0 Formula <br /> The impact analysis for the Stormwater system is based on square footage of impervious surface <br /> which creates an impact on the stomiwater system by land use type. Impervious surface is defined <br /> in Section 7.275, Eugene code, 1971 as "earth surface made impervious by development to vertical <br /> downward penetration by water". Impervious surfaces typically consist of concrete, asphalt and <br /> roofing materials. 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 the Stormwater SDC. <br /> The Stormwater SDC is an improvement fee, as new development will require the construction of <br /> additional system capacity. The per unit cost of additional capacity is based on existing system <br /> replacement value divided by impervious surface area. The total value of the system is estimated <br /> based on the replacement cost of the Stormwater System components which include miles of pipe <br /> and drainage channels, stormwater cleanouts, catch basins, inlets/outlets, and manholes. For <br /> current total value (Total Replacement Cost) of the stormwater system, see Table 6, section 1. <br /> Assessable costs were calculated using the approach specified in the City Code. The city assesses <br /> up to and including 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 system 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 Stormwater SOC. Figure 6 illustrates the calculation formula of the Stormwater SDC. The <br /> Stormwater SDC rates per unit of capacity can be found in Appendix G in the can-ent adopted SDC <br /> fee schedule. <br /> To determine a cost per square foot of impervious surface, the non-assessable portion (SDC eligible <br /> costs) of the stomiwater system cost was first divided by the total impervious acres within the city <br /> limits. The total impervious surface calculated for each development is assumed to contribute to the <br /> public stormwater system. The number of acres of impervious surface in each type of land use was, <br /> determined using runoff coefficients currently employed by the city. The cost per impervious acre <br /> is estimated based on dividing the non-assessable costs (eligible SDC Costs) by the total number <br /> of acres of impervious 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 /> March 01, 1997 Methodologies: City of Eugene SDCs Page E-1 <br /> <br />