02-16-2016 Planning Commission Packet

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, � engineered soil medium with an underdrain 6" above the native soils base to some na.tural infiltration. The basin's underdrain and overflow storm sewer will be routed downstream to the wetland. The proposed ponds will provide rate controt and water quality for the remaining roadway drainage prior to dischargi.ng to the onsite wetland. The stormwater management system will reduce the peak discharge rate offsite and it will provide water quaiity treatment ta reduce the phosphorous loading downstrearn. The design includes voiume reduct.ion in accordance ivICWD guidelines inciuding abstraction by filtratian, wetland buffer enhancement, tree preservation and ptanting and by a sma1l amount of infilt�ration where feasible. Wetlands The site consists of three wedands that were delineated by Jacobson�;nvironmental, PLLC. The wetlands were identif ed as Wetland 1,2, and 3. Wetlands 1 and 2 were identified as wet meadow/shallow marsh and aze classified as a"Vlanage 2"by Minnehaha Creek Watershed District. The final governmental review of the delineations determined that wetland 1 anc�2 are actually connected. Wetland 3 is a marginal seasonally flooded basin unclassified by MCWD. The plans propose an impact and removal of wetland 3. Preliminary meetings have occurred vv�th�ICWD and the Army Corps of Engineers and they are accepting of the wetland 3 removal. At that time, it was tentazively planne�for wetland mitigation to be done offsite. The proposed wetland buffers have been designed in accordance with the following MCWD regulations: VICWD classification of wetland 3 and 2 =Manage 2 _Vianage 2 base buffer width = 30' Manage 2 minimum app�ied buffer with =24' (per mcwd) • Applied buffer width=the rec�uired average buffer width for project and equals the base buf�'er width minus reductions far beneftcial slopes or soil canditions). • For every S%decrease in average buffer from 20%the base buffer width may be reduced by 2 feet. • Buffer widtli may vary(be averaged) as lang as min.Width is 50%of applied buffer width or max. Width is 24Q% of applied buffer width or less. The City of Orono has the following additional wetiand setba.ck requirement: • WetEand building setback=35'from wetiand edge or 10'from proposed wetland buffer,whichever is greater. The design started with a base buffer of 30' but reduced to 28' as a result of the very flat wetland buffers proposed. The 28' base buffer ca,u then be averaged with allowable min. buffer width of 14' and max.buffer of 56'. The bu.f�er area required was deterinined by taking the full lineai frontage of wetland 1 and 2 (as combined in final NOT}and multiplied by the requirec�28' buf�er width. i 'Wetland 1+2 Buffer Requirements Buffer Area Buffer Area Provide � Summa Pro osec! Required � Lineal ( Bonus Provided Class. Area Min, Max. Avg, Per Rqmt , � Frontage ; (exceeds 56'width) '_vlana e 2 3.07 ac 2,163 ft 15' S6' 28' 60,564 sf' GO 568 sf I 6,7C6 sf PRD. Rezonin�, and Preliminarv PIaE Submittal January_20 2016 Orono Preserve Page 6 of 7