MCAS Miramar Airport Land Use Compatibility Plan - San Diego ...

APPENDIX CAIRPORT LAND USE COMPATIBILITY CONCEPTSIn places where the noise exposure is not so severe as to warrant exclusion of new residential development,the ideal strategy is to have very low densities—that is, parcels large enough that the dwelling canbe placed in a less impacted part of the property.In urban areas, however, this strategy is seldom viable. The alternative is to encourage high-density,multi-family residential development with little, if any, outdoor areas, provided that the 65 dB CNELstandard and limitations based upon safety are not exceeded. Compared to single-family subdivisions,ambient noise levels are typically higher in multi-family developments, outdoor living space is less, andsound insulation features can be more easily added to the buildings. All of these factors tend to makeaircraft noise less intrusive.Sound insulation is an important requirement for residential and other noise-sensitive indoor uses inhigh noise areas. The California Building Code requires that sufficient acoustic insulation be providedin any habitable rooms of new hotels, motels, dormitories, and dwellings (other than detached singlefamilyresidences) to assure that aircraft noise is reduced to an interior noise level of 45 dB CNEL orless. To demonstrate compliance with this standard, an acoustical analysis must be done for any residentialstructure proposed to be located where the annual CNEL exceeds 60 dB. This Compatibility Planextends the 45 dB CNEL interior noise limit standard to single-family dwellings.Basis for Setting CriteriaCompatibility criteria related to cumulative noise levels are well-established in federal and state laws andregulations. The California Airport Noise Regulations (California Code of Regulations Section 5000 etseq.) states that:“The level of noise acceptable to a reasonable person residing in the vicinity of an airport is establishedas a community noise equivalent level (CNEL) value of 65 dB for purposes of theseregulations. This criterion level has been chosen for reasonable persons residing in urban residentialareas where houses are of typical California construction and may have windows partiallyopen. It has been selected with reference to speech, sleep and community reaction.”No airport declared by a county’s board of supervisors as having a “noise problem” is to operate in amanner that result in incompatible uses being located within the CNEL 65 dB contour. In San DiegoCounty, only San Diego International Airport has been so designated. Incompatible uses are defined asbeing: residences of all types; public and private schools; hospitals and convalescent homes; and placesof worship. However, these uses are not regarded as incompatible where acoustical insulation necessaryto reduce the interior noise level to CNEL 45 dB has been installed or the airport proprietor hasacquired an avigation easement for aircraft noise.As noted in the regulations, the CNEL 65 dB standard is set with respect to urban areas. For many airportsand many communities, CNEL 65 dB is too high to be considered acceptable to “reasonable persons.”Through a process called “normalization,” adjustments can be made to take into account suchfactors as the background noise levels of the community and previous exposure to particular noisesources. This process suggests, for example, that CNEL 60 dB may be a more suitable criterion forsuburban communities not exposed to significant industrial noise and CNEL 55 dB may be appropriatefor quiet suburban or rural communities remote from industrial noise and truck traffic. On the otherhand, even though exceeding state standards, CNEL 70 dB may be regarded as an acceptable noise exposurein noisy urban residential communities near industrial areas and busy roads.C–4 MCAS Miramar Airport Land Use Compatibility Plan (Adopted October 2008)