SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental Consequences5.3.10.4 Impacts from Maneuver TrainingSignificant Impacts Mitigable To Less Than SignificantImpact 1: Impacts to wetlands. Damage to wetlands occurs from off-road maneuvers during summerwhen the wetlands are unfrozen (Radforth and Burwash 1977). Impacts of military operations towetlands include breaking and crushing of plants and disturbance to soils or wetland substrate.Unintentional removal of vegetation from clearing with heavy equipment has also resulted in wetlanddegradation. These off-road impacts are less harmful during winter when wetlands are frozen andsnowpack protects vegetation. Impacts could occur to the surrounding environment as a result ofwetland disturbance and loss.Maneuvers can directly or indirectly alter the composition of plant communities and vegetativestructure. If wetlands are disturbed, small annual plants or invasive species often replace largeperennial plants. Maneuver impacts could decrease plant cover and densities of woody vegetation,resulting in reduced wetland function and habitat quality. In severe cases, damaged plant communitiescould be replaced by lower quality plant communities.Soils at disturbed sites also tend to become more compacted, which can affect seedling establishment,water and nutrient uptake, and root penetration. Reestablishment of plant communities may beimpeded by changes in soil properties. Soil erosion and transport may increase due to a loss instability from the removal of vegetative cover and the underlying supportive root system. Damage towetlands in northern climates, such as Alaska, can affect the insulating layer that protects permafrost(Section 5.3.2). This could create thermokarst conditions, possibly leading to subsidence, and couldincrease sediment delivery to nearby waterways. As a result, the water quality and aquatic habitatscould be degraded.Severe adverse impacts would be expected if the Stryker vehicle were used in summer. Use of theStryker vehicle in wetlands during summer, however, is not likely because the vehicles quicklybecome stuck. This would also result in wetland degradation (Bagley, unpublished data). Use of theStryker on wetlands during winter would result in minor damage to wetland plants, but minimaldamage to the root systems and soil substrate due to frozen conditions.The number of large maneuver rotations would not be expected to differ greatly from current IBCTrotations, but there are qualitative differences between IBCT and SBCT maneuver training. TheSBCT uses existing roads and trails more than the IBCT; however, it requires larger maneuver areas.The SBCT causes less surface disturbance during maneuver rotations and does less digging than theIBCT. There are more vehicles of heavier gross weight in the SBCT, and the quantity of small-unitcollective maneuver rotations would be expected to increase by 50 percent.Overall, impacts to wetlands from maneuver training would be significant but mitigable to less thansignificant. The amount of impacts from SBCT would increase with the need for larger training areas;however, the intensity of the impacts would decrease through their more frequent use of existingroads. Mitigation measures for impacts to wetlands from maneuver training would be the same asthose described in Impacts from Range Construction.Impact 2: Impacts to vegetation. Maneuver training could cause long-term adverse impacts tovegetation under Alternative B. Off-road maneuver training when vegetation is not dormant couldresult in vegetation damage. Vehicles can indirectly affect plant communities through soil compactionand by altering competitive relationships (Milchunas et al. 1998, 1999). Use of vehicles can result indecreased plant litter, ground cover and basal cover, and increased bare ground (Shaw and DiersingFebruary 2008 5-109 2/25th SBCT Final EIS