SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental Consequencesperiodically bare land susceptible to soil erosion. With the implementation of mitigation measures,soil erosion from cantonment construction would be less than significant.Regulatory and Administrative Mitigation 1: The Army would construct stormwater runoff controlstructures as part of standard construction BMPs, which would divert water from the constructionsites. Near the completion of construction, the Army would implement standard restoration BMPs,such as revegetation and landscaping to address any remaining exposed soils. Compared to existingconditions, increased soil erosion resulting from cantonment construction activities is expected to beshort-term, local, and less than significant with implementation of standard construction erosioncontrol BMPs and erosion and sediment control measures specified in the FTC INRMP and ITAMannual work plan.Less than Significant ImpactsExposure to Soil Contaminants. FTC has some of the highest naturally occurring documented levelsof Selenium in the United States. Naturally occurring selenium can acutely and chronically affectboth aquatic and terrestrial wildlife when land disturbances, such as excavation and trenching occur.Selenium that has leached into lower soil profiles over millions of years is exposed by landdisturbance and is taken up by non-native selenium-receiving plants, which then invade and overtakedisturbed sites. When selenium-loaded soils are exposed to water, selenium can directly enter surfacewater systems and biologically accumulate in the systems of aquatic and terrestrial animals. Deeprooted,selenium receptor plants can also redistribute selenium onto the ground surface and into thesoil. Other heavy metals naturally occurring at high levels on FTC, such as mercury, follow the samegeological and biological pathways as selenium. The impact associated with exposure to naturallyoccurring metals contamination during cantonment construction is considered less than significantbecause selenium study results, described in Chapter 3, provide FTC managers with site-specificselenium knowledge. Resulting management decisions ensure that land user activities do not create aselenium environmental reception hazard.Seismic Hazards. FTC is located within the low-risk Seismic Zone 1 (DECAM 2002b) and there islow potential for significant seismic activity near the cantonment. Any new structures developed inthe future would likely be designed to withstand the expected range of seismic shaking; therefore, theimpact is considered less than significant.5.4.2.2 Impacts from Range ConstructionSignificant Impacts Mitigable to Less than SignificantImpact 2: Soil Erosion. Construction of the two new weapons training ranges at FTC is expected tocause direct, short-term, localized soil erosion impacts when ground surfaces are disturbed toconstruct live-fire villages, trench lines, stationary armor targets, machine gun bunkers, and othertypical weapons training range features. However, the MPMG range would be developed byupgrading or renovating an existing range and the UAC would only involve 3 acres of newconstruction that would occur on a previously undisturbed site. Potential increases in soil erosioncaused by range construction would be temporary because construction of the structures and otherfeatures associated with weapons training ranges would create bare land only periodically. Comparedto existing conditions, increased soil erosion resulting from range construction activities is expectedto be short-term, local, and less than significant with mitigation.Regulatory and Administrative Mitigation 2: The Army would construct stormwater runoff controlstructures as part of standard BMPs, which would divert water from the construction sites. OtherFebruary 2008 5-134 2/25th SBCT Final EIS