SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental ConsequencesOff-road maneuvering by Stryker vehicles on DMR is expected to occur on 364 acres that are alreadycurrently used for other types of military vehicle maneuver training. The ATTACC model resultsindicate that land condition on DMR would substantially decline to a severely degraded conditionunder the assumption that maneuver training would be unrestricted over the entire accessible areawhere slopes are less than 30 percent. ATTACC modeling assumptions considered current landcondition on DMR as mildly impacted. However, under the Alternative A, it is expected that annualtraining load would increase from 2,286 MIMs to 4,837 MIMs (about a 111 percent increase).Moderate impacts on land condition (for example, reduction in vegetation and exposure of soils) areexpected to occur for a range of about 3,000 to 4,000 MIMs, and land condition is expected to declinemore rapidly when MIMs exceed 4,000. However, similar to the discussion on SBMR, if the Strykeris restricted to existing training roads, the land damage would be limited to the existing roads insteadof distributed over the entire DMR, but the restriction to the roads would mean that damage to theroad areas and the indirect impacts of increased surface runoff and erosion of the areas adjacent to theroads would be increased because the vehicle use would be concentrated onto a smaller area.Drum Road would be used by to transport vehicles and Soldiers to KTA. Off-road maneuver trainingis limited on KTA under Alternative A. Such training would include mounted maneuver training andother dismounted military training on approximately 4,569 acres at KTA. ATTACC modeling resultssuggest that a proportion of the land area in the maneuver areas could be affected. However, becauseKTA is currently used for military training activities, and the impact assessment is based on the levelof predicted use by the Alternative A, the modeling results predict a less than significant impact.Steep slopes occur on the margins of the CACTF. ATTACC modeling of the maneuver training areasat the CACTF suggests that the effects on land condition would be severe after the Alternative A isimplemented. These impacts would occur in addition to the ongoing erosion stresses due to knownlevels of public access and unauthorized use of portions of KTA.Increased soil erosion may result from mounted and dismounted SBCT maneuver training from use ofthe PTA Trail, the new BAX at PTA, and the Keamuku Parcel. The intensity of off-road vehicle usewithin the current boundaries of PTA would increase with implementation of the Alternative A. Offroadmaneuvering is expected to occur on approximately 1,800 acres currently used for other types ofmaneuver training on PTA and also on 23,000 acres not previously used for maneuvers on theKeamuku Parcel.ATTACC modeling for PTA assumed an increase in the number of MIMs from 16,293 under existingconditions to 34,480 (about a 111 percent increase). ATTACC modeling assumed that about 56,661acres, or about 50 percent of the total land area within PTA, is maneuverable, but that only about12,000 acres (11 percent of the total area) are currently being used. Much of this area is locatedadjacent to Saddle Road. The ATTACC model distributed the total MIMs over the available landarea, resulting in an average of 1.36 MIMs per maneuverable acre under existing conditions, andabout 2.87 MIMs per acre as proposed. Under existing conditions, it was assumed that the MIMsresult in “mild” impacts on land condition in the PTA boundaries, meaning that relatively littlerestoration is needed to sustain the land. This may be reasonably accurate on average, but it is notaccurate when applied to specific locations. For example, the INRMP for PTA identifies denudationof vegetation, major soil erosion, and severe windblown dust problems associated with maneuvertraining in Range 10. ATTACC modeling found that the Alternative A would result in degradation ofland condition to a “severe” condition on average, meaning that it would be much more difficult torestore and sustain the land over the long term than under existing conditions. The threshold for“severe” was assumed to occur at about 29,000 MIMs.For the Keamuku Parcel, the ATTACC modeling estimated that new SBCT maneuver training wouldresult in a total of 34,480 MIMs and degradation to a “moderate” land condition (lower than theFebruary 2008 5-11 2/25th SBCT Final EIS