With the coming of age of civil aviation in the 1930s and 1940s, the rural settings of many U.S. airports began to change. By the 1950s, expanding metropolitan centers surrounded formerly remote airfields with residential and commercial developments. As more powerful airliners rolled off the drawing boards, noise became an issue for those living nearby. With the arrival of commercial jets in the late '50s, neighborhoods under the flight paths of major airports became almost unlivable.

Mounting complaints, declining property values and class-action lawsuits by residents and cities prompted the aviation industry and state and federal governments to find solutions to the problem. California passed Title 21 and Title 24, mandating that airports and local governments provide mitigation measures. By 1979, Federal Aviation Regulations Part 150 enabled airports and local jurisdictions to apply for funding to either sound-insulate affected homes or acquire them and relocate their owners. In the 1960s and 1970s, the Los Angeles Department of Airports -- now Los Angeles World Airports (LAWA) -- removed 2,800 homes and relocated 7,000 residents from around Los Angeles International Airport (LAX).

Airport Noise Mitigation Program

In compliance with California regulations, the LAWA Noise Management Bureau (NMB) recently completed plans for an Airport Noise Mitigation Program (ANMP) to sound-insulate approximately 25,000 residences surrounding LAX. The construction phase of the program, begun in 1996, will be completed in the next five to seven years, at a cost of more than $200 million. Funding for the LAWA program is generated from "passenger facility charges," a $3 surcharge on departing passengers, authorized by the Federal Aviation Administration. Jurisdictions in the program areas can use LAWA funds and/or FAA grants to underwrite sound-insulation work in their respective areas. At present, ANMP applies only to residences. In the future, schools, churches, hospitals and other sensitive land uses may be added to the program.

To determine which land uses (number and type of parcels) qualified for sound-insulation, LAWA set up a sophisticated network of noise-monitoring stations in jurisdictions surrounding LAX. Data from the network is loaded into an ArcInfo GIS running a program that models noise contours at the 65, 70, and 75 decibel (dB) levels. The contours are overlaid on a parcel-level basemap. Detailed information on parcels within the contours is then obtained from the related database, also used to phase qualifying residences into the sound-insulation schedule.

NMB Environmental Supervisor Mark Adams pointed out that contours also help define costs. "For example, we know that a single-family home at the 75dB contour is going to cost more to insulate than one at 65dB. To estimate the total cost of the project and compute a construction schedule, we need a fairly accurate estimate of the number and type of homes at these noise levels. The contours help us to access that information."

Data, tables, maps and information on all ANMP phases were required to be submitted in a lengthy annual report to the California Department of Transportation's Division of Aeronautics. Preparation and publication of the documents required a month or more. Wyle Laboratories, acoustical engineers and prime contractor for the program, was responsible for coordinating development of the initial report. Psomas and Associates, civil engineers with GIS expertise, had the task of updating and expanding a parcel-level database, and developing tools to speed up preparation of ANMP reports.

According to Psomas Vice President Matt Rowe, the Santa Monica, Calif.-based firm began with a parcel-level database developed and maintained by NMB since the early 1980s. Although originally intended for a different project, the database covered much of the LAWA noise-mitigation planning area. An updated and expanded version, Rowe explained, could be used not only for spatial data management and noise analysis but also for monitoring the sound-insulation phase of the program.

"Obviously, LAWA is not going to insulate and/or acquire 25,000 properties all at once," he said. "They will use the database