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STORMWATER SITE PLAN <br />FEBRUARY 26, 2018 <br />MUKILTEO SCHOOL DISTRICT - TRANSPORTATION PAGE 9 <br />Rain gardens: The infeasibility criteria are found under BMP T7.30. <br />A rain garden is infeasible due to the lack of space on a redevelopment site. The proposed <br />pavement is at the top of a wall. The base of the wall will be the new buffer for the adjacent <br />wetlands. There are no pervious locations that are not critical areas. <br />Furthermore, Geotest's field tests found groundwater in Test Pit 2 at 2.8 feet below grade. The <br />rain garden would have 18" of amended topsoil and at least 6" of water ponding depth placing <br />the groundwater at less than 1 ft below the system. <br />3) Sheet Flow Dispersion or Concentrated Flow Dispersion <br />Sheet Flow Dispersion <br />Sheet Flow Dispersion is infeasible due to lack of space on the redeveloped site. All areas of <br />pervious surfaces are in critical areas. <br />Concentrated Flow Dispersion. <br />Concentrated Flow Dispersion is infeasible due to lack of space on the redeveloped site. All <br />areas of pervious surfaces are in critical areas. <br />Proposed: <br />The flow from new impervious will flow into the existing storm systems on -site. <br />P:\Work\Projects\2012\l2-185 Mukilteo SDME\DOC Mansportation Facility Drainage 12-185.doc <br />