environmental assessment us border patrol, tucson sector

3-401234567891011121314151617181920212223242526272829303132333435363738394041424344Acceptable noise levels have been established by the U.S. Department of Housing and UrbanDevelopment (HUD) for construction activities in residential areas (HUD 1984):Acceptable (not exceeding 65 dBA) – The noise exposure may be of some concern, butcommon building construction will make the indoor environment acceptable, and theoutdoor environment will be reasonably pleasant for recreation and play.Normally Unacceptable (above 65 but not greater than 75 dBA) – The noise exposure issignificantly more severe; barriers may be necessary between the site and prominentnoise sources to make the outdoor environment acceptable; special building constructionmay be necessary to ensure that people indoors are sufficiently protected from outdoornoise.Unacceptable (greater than 75 dBA) – The noise exposure at the site is so severe that theconstruction costs to make the indoor noise environment acceptable may be prohibitive,and the outdoor environment would still be unacceptable.As a general rule of thumb, noise generated by a stationary noise source, or “point source,” willdecrease by approximately 6 dBA over hard surfaces and 9 dBA over soft surfaces for eachdoubling of the distance. For example, if a noise source produces a noise level of 85 dBA at areference distance of 50 feet over a hard surface, then the noise level would be 79 dBA at adistance of 100 feet from the noise source, 73 dBA at a distance of 200 feet, and so on. Toestimate the attenuation of the noise over a given distance, the following relationship is utilized:Equation 1: dBA 2 = dBA 1 – 20 log (d2/d1)Where:dBA 2 = dBA at distance 2 from source (predicted)dBA 1 = dBA at distance 1 from source (measured)d 2 = Distance to location 2 from the sourced 1 = Distance to location 1 from the sourceSource: California Department of Transportation 1998All alternative sites are located in a remote rural area with no sensitive human noise receptorswithin a distance that would perceive any noise associated with the construction, operation, andmaintenance of the proposed FOB.3.10.2 Environmental Consequences3.10.2.1 No Action AlternativeImplementation of the No Action Alternative would have no impact on ambient noise quality inthe San Bernardino Valley. Indirect impacts from illegal activity would continue. More agentswould be required to patrol the remote eastern zones of the USBP Douglas Station’s AOR toaccount for the necessary drive time to their patrol areas. Indirect impacts from CBV activitiesand subsequent USBP interdiction activities would be greater under the No Action Alternativethan any of the other alternatives.Douglas FOB EADraftAugust 2011