02-19-2002 Planning Packet - Laserfiche WebLink

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following area of wetland replacement: 8,590 fr wetland fill x 2 = 17,180 ft* (0.39 acres) replacement. Replacement for wetlands that are filled due to the project will be done through the creation of a single mitigation site. The location of the mitigation site will be on-site and will be located south of the drainage ditch and along the eastern and southern property boundaries (Appendix B). Wetland Mitigation Design Site Selection The opportunity for on-site mitigation exists within the project area. Examination of the site indicated that there was potential to create new wetland by excavating an area adjacent to the ditch in the southeast comer of the property. Currently, this area of the property is a monotypic stand of buckthorn. Few other species have been observed. This is also true of the area north of the drainage ditch, which will be converted into upland buffer and a storm water treatment pond. This area is owned by the City of Orono and will be placed under an easement associated with the fire station. A utility easement may be placed over the storm water pond. Construction of the mitigation site will be concurrent with construction of the fire station. The site has not been used for prior wetland restoration or construction. Mitigation Design Plan The mitigation site is proposed to be constructed adjacent to the unnamed drainage ditch in the southeast comer of the property. This area of the property is currently undeveloped, and has become overgrown with buckthorn. This area is not wetland currently, and is not known to have been a wetland based on a review of historical aerial photographs. Plan sheets detailing the grading, planting, and erosion control for the mitigation site are available in Appendix B. Grading, Hydrolog}', and Soils Grading of the mitigation site has been designed as a floodplain wetland that will intercept floodwater and slow ly release it back to the ditch (Appendix B, Sheet 1). Functionally, this is similar to the wetland impacted by the construction of the fire station. Grading elevations have been designed so that the mitigation site will remain an average of one-foot higher in elevation than the adjacent ditch. This is lO keep the wetland isolated from the ditch except dunng flooding events. A low berm, designed to be one-foot tall by three-feet wide, will be constructed at the far eastern and western portion of the mitigation site where floodwater will enter and leave. The grading has Minnehaha Creek Watershed District Permit Application City of Ororw, Minnesota A-LONGL0204 00 Page 8