SBCT Final EIS - Govsupport.us

Chapter 5 – Environmental Consequencesconstruction equipment typically generate noise levels of 80 to 90 dBA at a distance of 50 feet. Withmultiple items of equipment operating concurrently, noise levels can be relatively high during the dayat locations within several hundred feet of active construction sites. The zone of relatively highconstruction noise levels typically extends to distances of 400 to 800 feet from the site of majorequipment operations. Locations more than 1,000 feet from construction sites seldom experiencesignificant levels of construction noise.Table 5-15Summary of Potential Noise Impacts from Alternative ALocationActivity Group SBMR DMR KTA/KLOA PTAImpacts from Cantonment Construction N/A N/A N/A N/AImpacts from Range Construction ☼ ☼ N/A ☼Impacts from Live-Fire Training 1 ☼ ☼/ N/A Impacts from Maneuver Training ☼ ☼ ☼/ N/A ☼ = Significant + = Beneficial Impact = Significant but mitigable to less than significant N/A = Not Applicable☼ = Less than Significant = No Impact1The proposed action would have a minor increase in noise impacts. The determination of significance is based onexisting noise levels.Construction activities would generate average daytime noise levels of about 55 dBA at the closestnoise-sensitive area. Because incremental Ldn contributions from construction activities would belower than 65 dBA at the nearest noise-sensitive areas (1,950 feet distant), impacts from constructionnoise would be less than significant. Most other construction projects would be further removed fromnoise-sensitive locations than the projects discussed above. Noise effects from these projects wouldbe less significant than the noise effects discussed above. No mitigation is necessary for impacts fromrange construction. Impacts from range construction would be less than significant.5.2.12.3 Impacts from Live-Fire TrainingSignificant ImpactsImpact 1: Noise from ordnance use. Noise levels from weapons firing and ordnance detonations arequite variable, with noise levels at long distances influenced in part by weather conditions. Smallarms firing can produce relatively high peak noise levels at localized areas around the range.Equations for estimating noise from small arms firing typically predict the peak unweighted dB value(Lpk). Because human hearing does not respond as rapidly to impulse noise events as do noisemonitoring instruments, the 1/8 second Lmax noise level measurement is a better indicator of howpeople perceive impulse noise than the unweighted peak dB measurement. The 1/8 second Lmaxvalue typically would be about 15 to 20 dB lower than the Lpk measure. Limited studies ofannoyance from noise near civilian shooting ranges have found that the A-weighted 1/8 second Lmaxvalue is the most useful predictor of annoyance. For most small arms types, the A-weighted decibelvalue would be about 3.5 dB lower than the unweighted decibel value. Thus, the A-weighted Lmaxfor small arms firing is about 20 dB lower than the peak unweighted dB value.As indicated by past estimates of noise contours around WAAF and by the noise contours for largecaliber weapons, firing noise levels associated with SBMR do not cause noise levels in off-postFebruary 2008 5-59 2/25th SBCT Final EIS