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. ~ <br />• <br />i ., : <br />6.2.4 Stormwater Runoff Pollutant Concentrations <br />The geometric mean stormwater runoff pollutant load concentrations for generalized land use <br />categories from the ACWA land use study were used in estimating the annual pollutant loads. <br />The pollutant concentrations used for updating the annual stormwater pollutant load estimates <br />are presented in Appendix G. <br />6.2.5 Rainfall <br />Average annual rainfall used in the model is 46 inches/year. The average rainfall is based upon <br />the long term rainfall record as recorded by the National Weather Service at the Eugene Airport. <br />6.3 Results <br />The results of the pollutant load calculations are presented in Table 6-1. It should be noted that <br />the annual pollutant load estimates presented in Table 6-1 do not include the same assumptions <br />as those made in the original Part 2 application and therefore, are not comparable with those in <br />the original application. The following is also noted in tfie original application 12: <br />As stated in EPA 's guidance manual for completing Part 2 of the permit <br />application (EPA, 1992), the estimates of annual pollutant loads may be <br />imprecise because of the limitations of currently available methods and <br />data. The relative values, and not the absolute values, of the pollutant <br />loads are intended by EPA to be used to assign priorities and allocate <br />resources for reducing stormwater pollution. <br />• Cite Strecker report if valid: <br />• Describe changes in land use and any system expansions. - <br />• Describe actions taken to adapt the stormwater program. <br />• Provide a finding' as to whether or not there will be a substantial increase in area, <br />intensity, or pollutant loads. <br />Table 6-2. Estimated Annual Pollutant Loads 2013 <br />Pollutant Load, Ibs <br />Total Dissolved Solids 12,698,852 <br />Total Sus ended Solids 9,004,609 <br />Biochemical Ox gen Demand ~ 1,326,705 <br />Chemical Oxygen Demand 6,575,876 <br />Nitrate 88,454 <br />Total Kjeldahl Nitrogen 160,630 <br />Total Phos horus 40,284 <br />Ortho-Phos hate 12,757 <br />Total Cadmium 105 <br />Total Co er 2,262 <br />Total Lead 3,382 <br />Total Zinc 18,852 <br />'Z City of Eugene XXX3CX, Part II, page 7=3. <br />10-83 <br />