Botany and Wetlands Study Report - McMillen, LLC

Botany and Wetlands Study ReportSoutheast Alaska Power Agency4.5.2 Young Growth ForestAs stated above, the majority of construction activities associated with expansion of the newdam would occur in areas already disturbed or developed for construction of the existing dam.Therefore, young‐growth forest would likely not be impacted by construction activities. Directimpacts to young growth would potentially result from inundation due to rising reservoir levels.As stated above, the majority of dam construction activities would occur in areas alreadydisturbed or developed for construction of the existing dam. Temporary staging areas andimprovements to existing roads; however, may be needed for dam construction and may impactyoung growth forest. Areas cleared for temporary staging areas would eventually revegetate andbecome young‐growth forest again. If widening of existing roads is required this could result inthe permanent loss of young growth forest. Similar to old‐growth forest, rising reservoir levelswould result in the permanent loss of young growth trees that would be submerged. Risingreservoir levels could also indirectly alter the nature and stability of the adjacent forest. Indirecteffects on young‐growth forest could occur through changes in hydrology and soil structure andstability not only from rising reservoir levels but also from fluctuating reservoir levels.Indirect effects to young growth could also occur from invasive plant spread. Due to the lack of adense forested canopy, disturbance to or adjacent to young‐growth forest could increase the riskfor invasive plant establishment. It is assumed that all young growth within the analysis area(approximately 4.6 acres) would be lost.4.6 Management Requirements and Mitigation Measures for GeneralVegetationThe effects of the Swan Lake Dam Expansion Project on forested portions would be limitedwithin the existing FERC boundary as much of the vegetation was removed prior to inundation;however, some additional removal adjacent to the reservoir may been needed. Approximately26 acres have been identified in the Lost Creek area, which were not part of the originalconveyed lands and that additional ground surveys determined the 350‐foot contour extendingfurther upstream. The entirety of this area is owned by the USDA Forest Service.Avoidance of impacts to productive old‐growth resulting from the proposed 15‐foot increase inpool elevation; however, would not be feasible. Trees that require removal within the activityarea (i.e., between 330 feet and 350 feet) will follow Forest Plan Standards and Guidelines aswell as BMPs. This will include conducting a timber cruise and working closely with the AlaskaDNR in the development of timber settlement agreement prior to removal. As previously stated,no timber would be cut and removed on Forest Service land.4.7 Identified Issues and Concerns to Wetland ResourcesImpacts to wetlands are based on the acres of wetland affected by inundation due to the 15‐footrise of reservoir levels to a new maximum pool elevation of 350 feet. As locations and extent ofSwan Lake Hydroelectric Project January 2013FERC Project No. 2911 Page 28 Version: Agency Review