Integrated Training Area Management EA and Final FNSI

Some mechanical operations would require pulling of trees or tree clumps, which would remove root ballsand associated soil. This would initially increase erosion by removing the root systems that help absorbwater and retain soils. However, downed trees would be piled and burned, chipped and spread out, orburied and left to decompose, all of which would return nutrients to soils rather than remove biomass offsite. Prescribed burning would be typically used for drop zone management and may result in increasederosion and potential permafrost impacts through increased soil temperatures. Projected burning projectsinclude 800 acres impacted at Donnelly Training Area (Appendix A).Best management practices for erosion control would be utilized in support of LRAM projects (AppendixB). These would include controlling runoff from land grading activities by creating temporary andpermanent diversions or dikes that would reduce slope length, collect storm water runoff, and deflectrunoff to outlets able to convey it by non-erosive means. Gradient terraces may be incorporated into thegrading plan to shorten the slope length and reduce storm water velocity. Check dams would be used toreduce the energy of storm water and help prevent erosion. Filter berms are temporary ridges that slow,filter, and divert flow from an open traffic area and act as an efficient form of sediment control. Grasslinedchannels would also be used in some areas to filter and convey runoff, and riprap would be used inareas of concentrated runoff to prevent erosion by stabilizing slopes, drainage ways, and outlets.Vegetated buffers would reduce the velocity of storm water runoff, help prevent soil erosion, provide anarea for the runoff to permeate the soil, and act as filters to catch sediment. Temporary storm draindiversions, earth dikes, and interceptor dikes would be used to contain storm water on-site or redirectstorm water to discharge into a sediment trap or basin. Subsurface drains would be used to preventsaturated soils that can hinder growth of certain types of vegetation and sometimes cause slope failure. Ahigh water table can saturate soils and prevent growth of certain types of vegetation. Mulch or sod wouldbe applied to stabilize exposed soils and reduce storm water runoff velocity. Permanent seeding would beused to reduce erosion, decrease sediment runoff from disturbed areas, and provide permanentstabilization in disturbed areas by establishing perennial vegetative cover. Soil roughening would often beused in conjunction with land grading and seeding practices for temporary erosion control to reducerunoff velocity, increase infiltration, reduce erosion, trap sediment, and prepare soils for seeding andplanting. Chemical soil stabilization would use soil additives or palliatives (including calcium chlorideand anionic asphalt, latex, or resin-water emulsions) to provide temporary soil stabilization. Soilpalliatives would only be used on mineral soils.Stand pipes (drain tubes placed perpendicular to the ground in areas susceptible to ponding) would beinstalled to maintain ponding water below levels that would overtop a road or pad and would helpminimize erosion due to flooding. Cobble drains would be installed underneath roads crossing subsurfacewater flows to prevent soil saturation and road impairment. Gabions would help reduce the impactof erosive, seasonal water flows. Log cribbing may be used to retain soil or gravel firmly in place.Asphalt or reinforced concrete may be used to control erosion (particularly, at stream crossings) or toreinforce specific erosion-prone areas along roadways or within training areas. Grid pavers made ofcement or plastic would be used to line ditches or stream bottoms where vehicles cross in order to preventerosion, stabilize the creek bottom, and minimize rutting or shifting of material.Construction sequencing, which involves timing land disturbance activities to minimize soil erosion andsedimentation, would be used. Construction entrances would be designed to minimize the amount of mudand sediment attached to motorized vehicles leaving a construction area. Temporary stream crossingswould be erected when necessary to provide streambank stabilization, reduce damage to streambeds orchannels, and minimize sediment loading from construction traffic. Soil retention structures and practiceswould be used to hold soil in place, prevent slope failure, or keep soil contained within a site boundary.Geotextiles would protect soil surfaces from wind and water erosion while also allowing vegetation_____________________________________________________________________________________________Environmental AssessmentUnited States Army Alaska, Integrated Training Area Management ProgramManagement Plan 21