Composite Training Unit Exercises and Joint Task ... - Govsupport.us

COMPTUEX/JTFEX EA/OEA Final Chapter 44.3.1.7.14 Underwater Explosives - Acoustic Effects Analysis ModelingMarine mammals may be harassed due to noise from operations involving underwater and near-surfacedetonations. The potential numbers and species exposed by explosive noise are assessed in this Section.The operations are described in Chapter 2 and include Air-to-Surface Missile/Bombing (ASM)Operations, Mining Operation, SINKEXs, Demolition (DEMO), Ship Mine Countermeasures (SMCM)Operations. The three primary sources of information necessary for estimating potential acousticexposure on marine resources are: (1) the number of distinct firing or test events; (2) the zone of influence(ZOI) for noise exposure; and (3) the density of animals that potentially reside within the ZOI.For the acoustic analysis, the exploding charge is characterized as a point source. The impact thresholdsused for marine mammals relate to potential effects on hearing from underwater detonation pressure andenergy. The same noise thresholds will also be applied to ESA-listed species.For the explosives in question, actual detonation would occur at depths of 5, 40, 65, or 150 feet below thesurface. Potential exposure of a marine mammal to detonation noise could theoretically occur at thesurface or at any number of depths with differing consequences. The acoustic analysis assumed thegreatest direct path for the harassment ranges to estimate the greatest impact range for the injurythresholds.4.3.1.7.15 Criteria and ThresholdsCriteria and thresholds that are the basis of the analysis of COMPTUEX/JTFEX noise impacts tocetaceans were initially used in U.S. Navy Environmental Impact Statements for ship shock trials of theSEAWOLF submarine and the WINSTON S. CHURCHILL vessel (U.S. Department of the Navy, 1998;2001) and adopted by the National Marine Fisheries Service (NMFS) (NOAA, 2001). Supplementalcriteria and thresholds have been introduced in the Eglin Gulf Test and Training ProgrammaticEnvironmental Assessment (U.S. Air Force, 2002) and subsequent Eglin Gulf Test and Training Letter ofAuthorization (LOA) (U.S. Air Force, 2003) permit request. Much of the information in this section istaken from the Eglin Air Force Base LOA permit request incidental to the Naval Explosive OrdnanceDisposal School testing within the Eglin Gulf Test and Training Range (U.S. Air Force, 2004) and theNMFS IHA authorization for conducting Precision Strike Weapon Testing and Training by Eglin AirForce Base in the Gulf of Mexico (NMFS, 2005).4.3.1.7.16 MetricsStandard impulsive and acoustic metrics were used for the analysis of underwater pressure waves in thisdocument.Energy flux density (EFD) is the time integral of the squared pressure divided by the impedance.EFD levels have units of dB re 1 Pa 2 -s. 1/3-Octave is the energy flux density in a 1/3-octave frequency band; the 1/3 octave selected isthe hearing range at which the subject animals’ hearing is believed to be most sensitive.4.3.1.7.17 Criteria and Thresholds: LethalityThe criterion for mortality for marine mammals used in the CHURCHILL Final EIS is “onset of severelung injury.” This is conservative in that it corresponds to a 1 percent chance of mortal injury, and yetany animal experiencing onset severe lung injury is counted as a lethal take. The threshold is stated interms of the Goertner (1982) modified positive impulse with value “indexed to 31 psi-ms.'” Since theGoertner approach depends on propagation, source/animal depths, and animal mass in a complex way, theFebruary 2007 4-48