Curecanti National Recreation Area: Personal Watercraft Use Enviornmental Assessment

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PURPOSE OF AND NEED FOR ACTION high concentration of exhaust from many engines, such as in an engine maintenance shop (Kado, Kuzmicky, and Okamoto 2001). At Curecanti, personal watercraft do not congregate in areas where exhaust would be concentrated. As engines are converted from two- stroke to four - stroke types, the emissions of PAH are expected to decrease. In August 2002, EPA proposed additional rules that would further reduce boating emissions. The proposal includes evaporative emission standards for all boats and would reduce emissions from fuel tanks by 80% (67 FR 157, August 14, 2002, pp. 53049 - 53115). Noise Personal watercraft - generated noise varies from vessel to vessel. No literature was found that definitively described scientific measurements of personal watercraft noise. Some literature stated that all recently manufactured watercraft emit fewer than 80 decibels (dB) at 50 feet from the vessel, while other sources attributed levels as high as 102 decibels without specifying the distance. None of this literature fully described the method used to collect noise data. The National Park service contracted for noise measurements of personal watercraft and other motorized vessels in 2001 at Glen Canyon National Recreation Area (Harris et al. 2002). The results show that maximum personal watercraft noise levels at 25 meters (82 feet) ranged between 68 to 76 decibels on the A- weighted scale (dBA). Noise levels for other motorboat types measured during that study ranged from 65 to 86 decibels at 25 meters (82 feet). Noise limits established by the National Park Service require vessels to operate at less than 82 dB at 82 feet from the vessel. Personal watercraft may be more disturbing than other motorized vessels because of rapid changes in acceleration and direction of noise. However, this regulation does not imply that there are no noise impacts from vessels operating below that limit. Noise impacts from PWC use are caused by a number of factors. Noise from human sources, including personal watercraft, can intrude on natural soundscapes, masking the natural sounds, which are an intrinsic part of the environment. This can be especially true in quiet places, such as in secluded lakes, coves, river corridors, and backwater areas. Also, PWC use in areas where there are non - motorized users (such as canoeists, sailing enthusiasts, people fishing or picnicking, and kayakers) can disrupt the "passive" experience of park resources and values. Komanoff and Shaw (2000) note that the biggest difference between noise from personal watercraft and that from motorboats is that the former continually leave the water, which magnifies noise in two ways. Without the muffling effect of water, the engine noise is typically 15 dBA louder and the smacking of the craft against the water surface results in a loud "whoop" or series of them. With the rapid maneuvering and frequent speed changes, the impeller has no constant "throughput" and no consistent load on the engine. Consequently, the engine speed rises and falls, resulting in a variable pitch. This constantly changing sound is often perceived as more disturbing than the constant sound from motorboats. PWC users tend to operate close to shore, to operate in confined areas, and travel in groups, making noise more noticeable to other recreationists (e.g., if identical boats emit 75 dB, two such boats together would be expected to emit 76 dB, 3 together would emit 77 dB, etc.) Motorboats traveling back and forth in one area at open throttle or spinning around in small inlets also generate complaints about noise levels; however, most motorboats tend to operate away from shore and navigate in a straight line, thus being less noticeable to other recreationists (Vlasich 1998). 10