SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental ConsequencesAdditional mitigation measures that would be implemented specifically to address impacts resultingfrom activities proposed under Alternative B are discussed in the appropriate activity group impactdiscussions below.5.3.2.1 Impacts from Cantonment ConstructionSignificant Impacts Mitigable to Less than SignificantImpact 1: Soil Erosion Resulting from Cantonment Construction Activities. Cantonment constructionto expand the motorpool parking area would be required. The motorpool would be expanded to adisturbed area adjacent to the existing parking area.Construction of the parking area would cause direct, short-term, localized impacts to soils.Construction activities, such as excavation, grading, trenching, and other earth-disturbing activities,could remove vegetation and disturb soils in the immediate construction footprint, increasing thepotential for soil erosion. Temporary soil disturbance caused by construction may also result inindirect, short-term soil erosion and delivery of sediment to streams and wetlands, as well as fugitivedust from heavy construction machinery. The impacts of surface water sedimentation and fugitivedust are discussed in Sections 5.3.3 and 5.3.11, respectively.Potential increases in soil erosion caused by construction in cantonment areas would be temporary,only periodically exposing bare land susceptible to soil erosion. Additionally, the Army wouldconstruct stormwater runoff control structures as part of standard construction BMPs, which woulddivert water from the construction sites. Near the completion of construction, the Army wouldimplement standard restoration BMPs, such as revegetation and landscaping to address any remainingexposed soils. Compared to existing conditions, increased soil erosion resulting from cantonmentconstruction activities is expected to be short-term, local, and less than significant.Regulatory and Administrative Mitigation 2: Implementation of standard construction BMPs and theland management practices specified in the USARAK INRMP and ITAM annual work plan wouldreduce these impacts to less than significant.Less than Significant ImpactsVolcanic and Seismic Hazards. Cantonment construction on FRA is not expected to have any effecton the frequency of volcanic eruptions or earthquakes, nor are cantonment improvements expected tobe susceptible to seismic hazards. The Anchorage area is seismically active and has experiencedearthquakes and ash fall from volcanic eruptions in the area. While the hazard associated withvolcanic eruptions and earthquakes is high if directed toward an area occupied by people or structuresduring construction, and the probability of seismic activity in the Anchorage area is moderately high,existing warning systems are expected to generally provide sufficient warning of an earthquake oreruption such that personnel and equipment would likely have time to evacuate. The impactsassociated with seismic and volcanic hazards during cantonment construction are considered less thansignificant.Exposure to Soil Contaminants. Because of the nature and type of training conducted in the past(especially prior to 1986), previously unidentified contamination could be found. All work involvingthe modification of facilities or excavation of any kind shall be coordinated via the USAG-AK "WorkClearance Permit" a minimum of five working days prior to mobilization to the site. Coordinationrequirements are outlined on the permit. Any soil or groundwater removed from the work site shall becontainerized in approved containers (specified in 49 CFR 178.500). Soil and groundwater shall notFebruary 2008 5-73 2/25th SBCT Final EIS