Mn Wetland Conserv Act Tech. Eval.findings

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i Inundation would have resulted in a conversion of wetland communities adapted to saturated soils(i.e.wet meadow communities and lowland wet forest communities)to the shallow marsh community that exists today.The culverts probably have had less of an impact over time.However,they are impounded and reduce flow out of the wetland and result in fluctuating hydroperiods of inundation that stress native wetland plant communities. III. Restoration Restoration In the WCA(8420.011 Subp 62)refers to the reestablishment of historic wetlands or wetlands that are degraded.The subject wetland has been degraded due to disturbance of its natural condition by human activities.This has resulted in low to moderate wetland functions and values under the existing condition.The wetland has moderate water quality and storm water retention functionality.However,it is nearly a monotypic stand of hybrid cattail and supports little wildlife. To truly restore the historic hydrology of the wetland that would have supported saturated soils and wet meadow communities,the culverts under Tonkawa Road would have to be expanded or lowered.Expanding or lowering the culverts would draw down water levels to promote saturated soils and the establishment of wetland vegetation communities adapted to these soil conditions.Drawing down water would be prohibited by the WCA.It would be considered an impact because it is an activity that drains a wetland and would likely reduce the overall size of the wetland.The applicant has proposed an alternative restoration technique that still achieves hydrologic and vegetative restoration,but will not result in loss of wetland quantity. The applicant has proposed restoring the historic wet meadow community by excavating approximately 2,588 cubic years of wetland soil from a 0.5 acre portion of the wetland and thin-spreading the material over lower portions of the wetland to a maximum elevation of 964.5 feet in order to maintain wetland conditions.A wet meadow seed mix will be broadcast over the thin-spread area to restore a wet meadow community.Plugs of marsh plant species will be installed in the excavated area.This will improve biodiversity of the wetland by creating two additional wetland community types.In addition to a lowland wetland forest community that exists now and will remain,the wetland will have a wet meadow component that will have greater floristic diversity and will attract birds and pollinators,as well as a deep marsh habitat that will promote amphibian and waterfowl habitat.The restoration will also Increase beta diversity at the landscape level by creating a diverse wet meadow wetland. High quality wet meadow wetlands are lacking within the Minnehaha Creek Watershed District because they have been degraded and are dominated by invasive species.The TEP recommended including a fallen log in the proposed deep marsh portion of the wetland to provide an area for heron and turtle perching,and to have an area for tadpoles to hide.The applicant agreed to include this. Aside from Improvements to the wetland itself,the proposed project includes restoration of the wetland buffer plant community through removal of invasive species and planting of native forest species.The proposal also includes improvements to water quality.The applicant plans to install two rain gardens that will treat an area of approximately 1.42 acres of runoff prior to entering the wetland.Therefore,the proposed restoration will increase the public value(MN Rules 8420.0522 Subpart 1)of the wetland by improving water quality,native plant habitat,and wildlife habitat.It will also promote advancement in wetland restoration science as an innovative and replicable wetland restoration technique. IV. Restoration Technique The success of the restoration depends on the ability to limit the growth of cattail in the wetland.Other cattail management techniques were researched and are outlined below.However,most are ineffective if not paired with the direct manipulation of water levels.The thin spreading of material is a technique that will manage cattails as well as provide an area for native wetland plant re-establishment. Cut and Flood The most effective cattail management technique is to cut the cattail stems and leaves and subsequently flood the wetland area for a prolonged period of time.This method works well because it precludes germination by reducing light to cattail seeds and it disrupts the function of the aerenchyma.Aerenchymha are channels in