Botany and Wetlands Study Report - McMillen, LLC

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Botany and Wetlands Study ReportSoutheast Alaska Power Agencyproposed project activities associated with construction of the expanded dam are not currentlyknown, acres of potential impacts to wetlands from these activities have not been calculated.Direct impacts to wetland resources from the proposed project include acres of wetland affectedby construction activities, either as permanent or temporary wetland fill, or as a result ofinundation due to the 15‐foot increase in maximum full pool reservoir elevation. The majority ofactivities associated with expansion of the new dam would occur in areas already disturbed ordeveloped for construction of the existing dam; however, wetland impacts in these areas couldpotentially be impacted. Direct impacts to wetland resources would primarily occur due toinundation.4.7.1 Effects from Rising Reservoir Levels Within the Analysis AreaRising reservoir levels would flood areas of emergent and forested wetlands and moss andforested muskegs within the analysis area. These areas of wetland resources would bepermanently lost due to inundation. Similar wetland communities may develop adjacent to thenew reservoir margins depending on steepness of the adjacent slope. Alternatively, risingreservoir levels could indirectly alter the nature and stability of the adjacent wetland vegetation.Approximately 75.9 acres of forested wetlands, 6.1 acres of emergent wetlands, 1.5 acres ofmoss muskegs, and 10.5 acres of forested muskegs would be permanently lost due to inundationfrom rising reservoir levels.Indirect impacts to wetland resources could also occur from rising and fluctuating water levels inthe reservoir in association with dam operation. Changes to hydrology in wetlands adjacent tothe new maximum full pool reservoir elevation could impact the functions of these wetlands andalter the species composition of these areas. Alteration of species composition and hydrologicregimes in these wetlands could also result in the loss or modification of wetland habitat.Indirect impacts on wetland habitat through changes in hydrology and soil structure and stabilitycould occur not only from rising reservoir levels but also from fluctuating reservoir levels.4.7.2 Effects from Construction Activities Outside the Analysis AreaNo forested wetlands or moss muskegs would be directly or indirectly impacted by constructionactivities associated with expansion of the new dam. Small amounts of emergent wetland couldbe directly impacted from construction of temporary staging areas and widening or improvingexisting roads. Emergent wetlands in areas where construction activities would occur are highlydegraded and located in heavily disturbed areas (i.e., adjacent to roads and in roadside ditches).Impacts to wetlands from construction of staging areas would be temporary. Impacts towetlands would be permanent in areas where existing roads are widened or improved.Functions and values of temporarily impacted emergent wetlands would be restored followingthe removal of temporary fill and revegetation. Wetland acreage permanently impacted wouldresult in a loss of wetland functions, including water quality improvement, wildlife habitat, andhydrologic functions. However, wetlands that would be permanently impacted are highlySwan Lake Hydroelectric Project January 2013FERC Project No. 2911 Page 29 Version: Agency Review
Botany and Wetlands Study ReportSoutheast Alaska Power Agencydegraded and are associated with or adjacent to heavily disturbed areas. Additionally,permanent loss of emergent wetland acreage from construction activities is expected to beminimal.Indirect impacts to wetland resources could occur from changes to hydrology associated withconstruction activities. If hydrology of wetlands adjacent to construction activities is altered itcould result in a change in the species composition and a loss of wetland functions. Indirecteffects to emergent wetlands could also result from invasive plant spread. Ground or soildisturbance to or adjacent to wetland resources would increase the risk for invasive plantestablishment.4.8 Management Requirements and Mitigation Measures for WetlandResourcesThe effects of the Swan Lake Dam Expansion Project on wetlands would be limited, to the extentpossible, through the site‐specific application of Forest Plan Standards and Guidelines as well asBMPs for all action alternatives. Temporary staging areas and road improvement or wideningactivities would be constructed in accordance with the BMPs identified in FSH 2509.22.Due to the preponderance of wetlands along the perimeter of Swan Lake, avoidance of impactsto wetlands resulting from the proposed 15‐foot increase in pool elevation; , would not befeasible.5 REFERENCESAKNHP (Alaska Natural Heritage Program). 2008. Alaska Natural Heritage Program Rare VascularPlant Tracking List. Available online at: http://137.229.141.57/wpcontent/uploads/2010/11/Rare‐Plant‐List‐2008.pdf.AKNHP. 2012. Alaska Natural Heritage Program Rare Vascular Plant Tracking List. Availableonline at: http://aknhp.uaa.alaska.edu/botany/rare‐plants‐species‐lists/2012‐rarevascular‐plant‐list.Connor, Cathy, and Daniel O’Haire. 1988. Roadside Geology of Alaska. Mountain PressPublishing Company, Missoula, Montana.Consortium of Pacific Northwest Herbaria. 2012. Herbarium Specimens from the PacificNorthwest. Available online at: http://www.pnwherbaria.org/index.phpCooke. 2005. Cooke Scientific Services, Inc. Pacific Northwest Forested Wetland LiteratureSurvey Synthesis Paper. April 2005. 95 pp.Swan Lake Hydroelectric Project January 2013FERC Project No. 2911 Page 30 Version: Agency Review
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