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Roadway improvement projects in Urban Areas without Regional Ponding proved to be the most difficult setting for meeting the District standards. The main reasons for tlus difficulty were: . Limited vacant land . Added design constraints such as existing grades and utilities . General hesitancy by city staff to incorporate small scale stormwater practices tlu'oughout the road cOlTidor. The permitting history of roadway improvement projects within tius setting shows, nevertheless, an attempt to incorporate local water quality ponds within available open-space. Again, this was problematic as there was usually not sufficient vacant land for a traditional pond. In some cases, other smaller measures such as rain gardens, infiJtration trenches and structural devices were incorporated. NEED FOR SPECIFIC ROADWAY STANDARDS The assessment of historic road permitting reveals that the stormwater management standard for roadway projects is not defined as extensively as it could or should be. This review also found that there are varying levels of resource impact for different types of road projects. Therefore, it would be preferable for specific stOlIDwater standards for each type of roadway project to be defined in the District Rules. Types of roadway projects could be categorized as: . New Constmction . ExpansionJReconstmction . Ruml to Urban (the addition of curb and gutter or additional stOlIDsewer) . Mill & Overlay In addition to clarifying the District Rules, the other main benefit of incorporating explicit roadway standards would be the recognition of the constraints typically associated to these projects. Tlus will allow provisions for increased flexibility in the means to attain District standards. For instance, recognizing and giving credit for the fact that infiltration practices are also very efficient water quality practices is paramount. Such approach is typically not considered in development of stOlIDwater management plans for roadways. APPROACH TO ROADWAY STANDARDS The first step towards defining roadway standards was to deterIDine tire amount of average annual runoff from a site that would have to be retained via BMPs (e.g. raingardens, trenches) to meet the cUlTent District standards for total phosphorus removal (60%). This arumal mnoff volume was then cOlTelated to the rainfall event that should be used as the basis of for BMP sizing. This approach has tlu'ee main benefits: I. Effective Peliormance: Manage sufficient runoff volume on an annual, average-year basis to still protect resources to the level intended by the District's Rules. Emmons & Olivier Resources, Inc. Page 2 of7