Volpe Journal Spring 98
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Restoration of Natural Quiet:
The Department of
Transportation's Initiatives in the National Parks
Every summer, millions of Americans travel to our national parks to experience nature and spectacular land forms. In increasing numbers, park visitors are complaining that their experiences are diminished by the intrusion of aircraft and aircraft noise, primarily from local operators of tour helicopters and fixed wing aircraft. Responding to legislation and a special Earth Day message from President Clinton, the Federal Aviation Administration and the National Park Service are working jointly to develop a National Rule to mitigate the impact of overflight noise on these treasured landmarks. Gregg Fleming and his team at the Volpe Center Acoustics Facility are playing a major role in the development of a scientific basis for the National Rule.
Although America's National Parks are administered by the United States Department of the Interior's (USDOI) National Park Service (NPS), since the passage of the 1958 Federal Aviation Act, the airspace above them has fallen under the jurisdiction of the United States Department of Transportation's (USDOT) Federal Aviation Administration (FAA). This act specifically requires the FAA to help preserve public parks and recreation lands. The FAA has made reduction of aircraft noise an important objective, and the Human and Natural Environment Section of the Secretary of Transportation's Strategic Plan, 19972002, has designated it a key target area.
The current cooperative effort between the FAA and NPS originated in the 1980s, when the NPS responded to growing public concern about excessive aircraft activity and noise over the Grand Canyon National Park (GCNP). Despite the regulation of tour flights over the GCNP, their continued growth led park managers to raise similar concerns about ever-increasing noise levels. Beginning in the summer of 1986, the FAA initiated regulatory action to address increasing air traffic over GCNP. In March 1987 it issued Special Federal Regulation (SFAR) 50, which, among other goals, was meant to reduce the impact of aircraft noise on the park environment. SFAR 50 was later refined with the release of SFAR 50-2 in May 1988. The primary goal of SFAR 50-2 was the restoration of natural quiet to GCNP. (View Photo: Grand Canyon National Park)
CONGRESS ZEROES IN
The National Parks Overflights Act of 1987 (Public Law 100-91) addressed the problem directly, saying that "a significant adverse effect on the natural quiet and experience of the park and current aircraft operations at the GCNP have
Specifically, the President required
the Secretary "to continue the
ongoing development of rules...to
address overflights of the National
Parks," and went on to note that
"the Secretary of Transportation has
both valuable expertise and
regulatory authority" to address
certain overflight issues.
raised serious concerns regarding public safety including concerns regarding the safety of park users." The Act required the Department of the Interior (DOI) to submit to the FAA recommendations to protect the natural resources of the GCNP from the adverse effects of aircraft overflights. Specifically, the NPS was required to provide for "the restoration of natural quiet and experience" in the GCNP, prohibit most flights below the rim of the Canyon, and designate flight-free zones. The explicit recognition of "natural quiet" as a significant social value happened much earlier and is in the language of the 1975 GCNP Enlargement Act.
In response to the directive to report back on noise-related progress, as required by Public Law 100-91, the NPS produced the important 1994 Report to Congress, published in July 1995 as the Report on Effect of Aircraft Overflights on the National Park System. This landmark report, among other things, made numerous recommendations for changes at GCNP to existing special flight restrictions, including expanding flight-free zones, phasing in use of quieter aircraft, instituting flight-free time periods, and having park managers monitor noise in cooperation with the FAA.
ThenSecretary of Transportation Federico Pe&#ntilde;a and Secretary of the Interior Bruce Babbitt formed an inter-agency working group (IWG) in December 1993 to address the overflight problem in all affected national parks. The FAA's role in the IWG focuses on balancing aviation safety and the efficient use of airspace with environmental values. The NPS focuses more on the effects of public use of the area at ground level, and on enjoyment of the parks.
The most recent congressional action is the National Parks Overflights Act of 1997, introduced by Senator John McCain (R-AZ), Chair of the Senate Commerce, Science, and Transportation Committee and an outspoken leader on this issue. Senator McCain authored the similarly titled 1987 legislation, and in this "preventative legislation" he pushed for prioritizing implementation of restrictions at the parks most seriously affected, promotion of quieter aircraft technology, and setting of minimum altitudes. Senator McCain, looking back over 10 years of legislative history, noted that "this long-fought battle has taught me that we cannot afford to wait until natural quiet has been lost before we take steps to preserve and protect that resource."
THE PRESIDENT SPEAKS
Another milestone in this legislative saga was President Clinton's 1996 Earth Day Memorandum, which specifically directed the Secretary of Transportation "to continue the ongoing development of rules . . . to address overflights of the national parks." The memorandum went on to note that "the Secretary of Transportation has both valuable expertise and regulatory authority" to address overflight issues. Specific actions suggested by the President included issuing draft regulations that "at a minimum, establish a framework for managing air traffic over those park units identified in the 1994 [Report to Congress] study for (1) resolution of airspace issues and (2) maintaining or restoring natural quiet." In response to this directive, in December 1996 a draft Notice of Proposed Rulemaking (NPRM) was issued by the FAA together with the Environmental Assessment (EA) for a proposed airspace redesign over GCNP. The Volpe Center Acoustics Facility was responsible for the noise-related analyses in support of these documents (View Figure 1; View Figure 2).
THE PEOPLE SPEAK
Public review and comments in response to the NPRM and EA for GCNP drew much interest, given the potential for conflict between the tour operators and environmental advocates. Tour flight proponents prophesied the collapse of the industry and complained about the cost of acquiring quieter aircraft. Jim Petty, president of Air Vegas and chairman of the U.S. Air Tour Association, testified, "until there are measurable improvements in quiet aircraft technology, we oppose the disqualification, elimination, or preclusion of any air tour aircraft" from operating in the parks. The air tour industry also raised safety concerns over compressed flight periods that resulted from extended no-fly time curfews. Other aviation industry representatives argued that air tourists were becoming the object of discrimination and that these restrictions would prevent the elderly and physically disabled from enjoying the parks. This constituency also argued that airborne environmental impact should be compared and balanced with the trash, noise, automobile pollution, congestion, and general trampling by terrestrial visitors to the GCNP.
Rob Smith of the Sierra Club argued that "the one great value of our national parks should be that visitors don't have to listen to the clatter of everyday life." He noted that with 95,000 air tours flying 800,000 passengers per year, "visitors don't have a park experiencethey have an airport experience" in the GCNP. Many environmental groups and individuals expressed frustration with NPS standards for restoration of natural quiet that they felt to be too liberal. Specifically, some groups discounted the value of flight-free zones in reducing noise impacts to sensitive areas, primarily because aircraft noise can travel several miles laterally beyond "theoretical" zones. This group also argued that commercial activities on the ground in national parks are heavily regulated, and air tour companies should be held equally accountable.
Native American groups also expressed their concern over new flight-free zones that, they argued, relocated noise impacts from the GCNP to the skies over their tribal lands. These groups also testified that the impacts were severe enough to trigger a full Environmental Impact Statement (EIS).
THE BURDEN OF PROOF
The Administrative Procedures Act directs public agencies to avoid arbitrary and capricious rulemaking and holds them to rational, reasoned, scientific, and data-based methodologies. Over the past eight years, the NPS has conducted fairly extensive noise measurements in GCNP and Hawaii's Volcanoes and Haleakala National Parks. In addition, limited noise data were also collected by the NPS at Bryce Canyon National Park (BCNP), Cumberland Island, Yosemite, and Glacier National Parks, as well as Mount Rushmore National Memorial and Petroglyph National Monument.
The challenge for the Volpe Center Acoustics Facility, in support of the FAA Office of Environment and Energy, is to provide the technical leadership needed to develop a scientific basis for a National Rule on overflight noise. This will be accomplished by improving and building upon the technical work performed previously by the NPS. The first step in that process was the measurement of quantitative noise dose along with simultaneous human-response sampling (dose-response) in BCNP during the summer of 1997.
THE MEASURE OF THE THING
For Gregg Fleming and his team at the Volpe Center Acoustics Facility, taking on a critical role in helping to develop the scientific basis for a National Rule on aircraft noise in the parks presents numerous challenges. Dose-response studies, based on the methodology developed and refined in the 1997 BCNP study, are slated for five more parks by the year 2000.
Specifically, the methodology consists of the following four types of quantitative measurements, which will be taken simultaneously at an acoustic monitoring site by a highly sensitive, low-noise microphone system:
- Continuous measuring of one-second sound-level data;
- Periodic digital audio tape (DAT) recording of sound;
- Continuous logging of all audible aircraft and non-aircraft sounds; and
- Continuous logging of meteorological data, including temperature, relative humidity, wind speed, and direction.
Noise monitoring equipment is located at a position adjacent to the park trail, where it cannot be seen by passing visitors (View Figure 3). An aircraft observer log is maintained that classifies noise events into one of three categories: aircraft, human related but not from aircraft, and natural. If several of these categories occur simultaneously, the observer can rank them in a hierarchy, with aircraft taking the highest priority and natural ranking at the bottom of the scale. For example, if a bus and an aircraft are audible at the same time, the aircraft would be documented, and if a natural noise and a bus are heard together, the bus noise is logged. In this hierarchy, natural sounds are documented only in the absence of sounds of human origin.
Subjective human response to the aircraft noise is documented via a park visitor survey process. The goal is 300 park visitors at each measurement site. A team of trained field interviewers administers an on-site survey via a formal questionnaire. These interviewers are responsible for tracking the arrival times and movements of visitors in the park, which will be used to help compute the visitors' noise-related descriptors, or dose. Initially, questionnaires will be administered to all visitors passing the monitoring site who are English speakers and over the age of sixteen. Large numbers of visitors in excess of the interviewing team's capacity will trigger use of a random sampling methodology.
The noise monitoring data are then correlated with the visitor response. Data analysis takes into consideration such factors as percentage of time aircraft were audible, equivalent sound level due to aircraft, change in sound level due to aircraft, and some variant on the number of aircraft events experienced by a visitor. The goal of the analysis is to determine the point at which the average park visitor becomes "annoyed" by aircraft sounds.
LOOKING TO THE FUTURE
Gregg Fleming and his team face three more years of exhaustive research in the national parks before the data are in place to form a basis for the National Rule on overflight noise. Their current schedule anticipates dose-response measurements at five additional parks over the next three years. At the end of this process, they expect to have a strong database and proven methodology that will enable the DOT/FAA and the DOI/NPS to develop a set of regulations that are far from "arbitrary and capricious."
Contributor: Gregg Fleming
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