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• Quantification of the vehicular traffic in the municipal separate storm sewer at <br />levels that would correspond to a high pollutant loading in stormwater discharges; <br />Other indications of increased potential for stormwater pollutant loading, <br />including a large non-resident population (such as seasonal or year-round tourism, <br />university students, adjacent military bases, or other types of commuters) or high- <br />use commercial traffic areas. <br />Factor 3: Does the municipal separate storm sewer serve a substantial population or area? <br />Management of stormwater runoff from growing municipal separate storm sewers is a <br />primary goal of the regulations. High growth may be measured by a rate of increase in <br />population, or directly by the number of people added, or by the increase in the amount <br />of impervious surfaces in the municipal separate storm sewer. Ecology will evaluate <br />whether the municipal separate storm sewer has experienced high growth by one or <br />more of the following measures: <br />• Residential population has grown or is projected to grow by a rate of 15% (the <br />average rate of growth in Washington State from 1990-2000) or more within a 10 <br />year period; this applies only to municipal separate storm sewers serving a <br />minimum population of 1,000. <br />• The municipal separate storm sewer is projected to serve a population of 10,000 <br />or more outside an Urbanized Area, or a population of 1,000 or more inside an <br />Urbanized Area, when the next census takes place. (Note: Municipal separate <br />stone sewers that met this criterion for the 2000 census have already been <br />designated by Ecology as regulated municipal separate storm sewers.) <br />• The amount of total impervious area served by the municipal separate storm <br />sewer has increased by a rate of 10% or more within a 10 year period; this applies <br />only to municipal separate storm sewers serving a minimum population of 1,000. <br />Ecology's determination will be based on the best available information, including the <br />latest U.S. Census Bureau or State of Washington Office of Financial Management <br />data. <br />Factor 4: Is the municipal separate storm sewer contiguously located to an already regulated <br />municipal storm sewer? <br />Potential impacts on a neighboring regulated municipality and shared water bodies will <br />be considered for jurisdictions that are directly adjacent to an already regulated <br />municipal separate storm sewer. <br />Factor 5: Is the municipal separate storm sewer physically interconnected to another, ahead <br />regulated municipal storm sewer? <br />If a municipal separate stone sewer is physically interconnected to another municipal <br />separate stone sewer that is regulated by the NPDES stormwater program and <br />contributes substantially to the pollutant loading in the regulated municipal separate <br />storm sewer, then it must be designated as a "regulated municipal separate storm <br />sewer." Ecology will determine whether the physically interconnected municipal <br />separate storm sewer contributes substantially to the pollutant loadings of the already <br />regulated municipal separate storm sewer. <br />To determine whether a physically interconnected municipal separate storm sewer is a <br />"substantial contributor" to the regulated municipal separate storm sewer, Ecology will <br />consider the following factors and any other factors Ecology's determines are <br />appropriate: <br />Modified October 13, 2014 2 <br />