SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental Consequencesranges because it is based on sampling that was purposely selected for areas expected to containhigher than average concentrations of contaminants. Also, the sample results indicate that thecontaminants occur in some areas but not others, so the distribution is not even. Many contaminantsare not highly mobile in water, and sediments may require many months or years to migratedownslope to streams. Meanwhile, some contaminants, such as explosives, would be undergoingchemical degradation.The assumption of the lifetime health advisories is that the water is consumed at a rate of 2 liters perday for a year. The stream water would not be consumed without filtration, and filtration wouldremove the contaminants because they are bound to the suspended sediment. Therefore, after dilutionin the main stems of Kaukonahua or Waikele Streams, the concentrations of contaminants would bebelow detection levels and would not reduce the beneficial uses of the streams.A similar analysis can be conducted for metals using the concentrations observed in the soil sampleson the ranges. The results would show that metals could be transported to streams at concentrationsthat might exceed drinking water standards. The loading rates would increase with increased soilerosion. Implementing the mitigation measures discussed in the mitigation section would reduce theimpacts on surface water quality to acceptable levels.Regulatory and Administrative Mitigation 3: Implementing the ITAM and ORAP programs asdescribed above would reduce water quality impacts from soil contaminants to less than significant.Less Than Significant ImpactsImpacts on surface water and groundwater quality. Alternative A may increase the amount ofexplosives residues in soils. It also may result in dispersion of these residues by wind and watererosion. PTA lacks any permanent streams or water bodies; therefore, impacts on surface water wouldbe of short duration, and if they occurred, are expected to be less than significant. Due to the depth ofgroundwater beneath the PTA and SBMR and the relatively low concentrations of explosives residuesin soils, groundwater is not expected to be affected.The following mitigation measures would be implemented to protect water resources from potentialimpacts resulting from live-fire training. The Army would develop and implement a DuSMMoP forthe training area. The plan would address measures such as, but not limited to, restrictions on thetiming or type of training during high-risk conditions, vegetation monitoring, soil monitoring, andbuffer zones to minimize dust emissions in populated areas. The plan would determine how trainingwould occur in order to keep fugitive dust emissions below CAA standards for PM 10 and soil erosionand compaction to a minimum. The Army would monitor the impacts of training activities to ensurethat emissions stay within the acceptable ranges as predicted and environmental problems do notresult from excessive soil erosion or compaction. The plan would also define contingency measures tomitigate the impacts of training activities that exceed the acceptable ranges for dust emissions or soilcompaction.5.2.3.4 Impacts from Maneuver TrainingSignificant Impacts Mitigable To Less Than SignificantImpact 4: Impacts on surface water quality from nonpoint source sediment loading. Trainingactivities are expected to include an increase in mounted maneuver training area in the SRAA, KTA,and in SBER compared to existing conditions. The resultant increase in soil erosion is likely to resultin an appreciable increase in suspended sediment in adjacent streams. Of most concern are the majorFebruary 2008 5-20 2/25th SBCT Final EIS