SBCT Final EIS - Govsupport.us

Chapter 3 ⎯ Affected EnvironmentParcel are subject to wind erosion at lower wind speeds than most soils. Wind speeds on the westernside of PTA exceed the likely wind erosion threshold of 12 mph about 15 percent of the time.Although Hawaii is in a PM 10 attainment area under the CAA, the Island of Hawaii and the surroundingland at PTA have experienced discrete events in which dust impacts have had adverse effects.PM 10 emissions are important because they are easily airborne and are small enough to be inhaleddeep into the lungs, creating potential adverse health effects. Because of the extremely small particlesize of the soils found on Keamuku Parcel, the particles easily become airborne during high-windevents and other disturbances once vegetation has been removed. In July 1999, a severe dust stormresulted from wind blowing over areas denuded of vegetation by a recent fire. The result was fugitivedust emissions at high enough levels to require temporary evacuation of residences at Waikii Ranch.In January 2006, the Army installed seven air-monitoring stations around PTA (Morrow 2007). Thepurpose of the monitors was to monitor concentrations of total suspended particulate matter (TSP)and particulate matter (PM 10 ). TSP was included because it is more representative of fugitive dustthan the finer, inhalable PM 10 .The monitors were installed as close to PTA’s boundaries as access andsafety would allow. Between January 29, 2006 and June 30, 2007, the monitors sampled particulatematter following the EPA’s once-every-6-days schedule.Analysis of the data collected during the sample period indicates that concentrations of particulatematter at PTA under current activity levels are well within federal and state air quality standards(Morrow 2007). The 24-hour PM 10 concentrations at the seven sites ranged from 0 to 72 µg/m 3 with amean value of 7.2 µg/m 3 for all sites. The federal and state standards for PM 10 are 150 µg/m 3 (24-hour) and 50 µg/m 3 (annual average). The 24-hour TSP levels ranged from 1.4 to 132 µg/m 3 for allsites with an annual mean of 14.4 µg/m 3 . Although there are no longer federal or state standards forTSP, the former standards were the same as the PM 10 standards cited above.Sampling particulate matter occurred during training of the 2/25 th SBCT in 2007. This training includedboth maneuver and live fire training (small arms training, and mortars). All 24-hour PM 10 concentrationsfrom the sampling events were below the federal and state standards for PM 10 of150 µg/m 3 (24-hour).3.1.11 NOISENoise levels are commonly referenced as average A-weighted decibels (dBA) levels for stationarynoise sources, or peak dBA levels for brief noise events and noise sources moving past a fixed point.Decibel (dB) scales are not linear. Apparent loudness doubles for every 10-dBA increase in noiselevel, regardless of the dBA values. Data have been compiled from various published sources, noisemonitoring studies, and noise modeling analyses.Although the A-weighting scale is the most widely used decibel weighting procedure, other weightingscales have been developed. The C-weighted scale and unweighted decibel values are commonly usedfor blast noise, sonic booms, or other low-frequency sounds capable of inducing vibrations in buildingsor other structures. In addition, evaluations of blast noise or sonic boom events sometimes use apeak overpressure measurement. The peak overpressure normally is an unweighted decibel measurementfor the dominant octave band or ⅓ octave band component of a sound. In most cases, the specificoctave or ⅓ octave band for the peak overpressure measurement is not reported. The peak overpressurelevel will be slightly lower than the corresponding composite unweighted decibel measurement.Varying noise levels often are described in terms of the equivalent constant decibel level. Equivalentnoise levels (L eq ) are not a simple averaging of decibel values, but are based on the cumulative acous-February 2008 3–82 2/25th SBCT Final EIS