2300 KASCH PARK RD 2018-01-01 MF Import

Expanded Environmental Checklist Prepared for the Office of Cortmunit,y Planni�g S�ohomish County, Washington Proposal: Cortmunit;y Transit Operating Base Page 4 field noise monitoring equipment was place6 in the residential neighborhood at a point approximately 4,000 feet to the east of the site of the Operating Base. This equipment was used to help establish existing ambient non-aviation noise levels near the airport. Testing was conducted in 1980 during preparation of the Paine Field Compatibility Study. Although the tests were lirnited in duration, an ambient noise level of 48 dBA was determined to be useful for a point near 9th Ave. SW and 96th St. SW. This level of bar_kground noise was typical of reside�:tial areas near the airport (excluding airport noise), and can be considered to be appropriate for those residences located clasest to the project site� Forty-foot buses, constructed since 1976, generate approximately 76 dBA duriny acceleration when detected by a receiver fifty fee' from the Dus. Older buses can produce up to 82 dBa, as do sixty-foot articulated buses under similar conditions. A "worst case" scenario could envision the simultaneous acceleration of ten articulated b��ses. Although the probability of such an event is extremely remote, this example is useful for understznding the pote�tial noise impact of the Operating Base' s activities upon the nearest residential units. Assuming the simultaneous acceleration of ten articulated buses, an observer stationed fifty feet away would hear a noise level of 92 dBA (82 dBA + 10 dBA). However, since the nearest residence to the hypothetical event is 1,600 feet away rather than at fifty feet, 30 d6A' s should be subtracted for a resulting 62 dBA. Substituting ten forty-foot buses (new) would result in a noise level of 56 dBA as perceived from the nearest house. This level is S dBA ab�ve the assumed ambient level. The derived hypothetical noise levelc of 62 and 56 d6A compare favorably with the "Qualitative Descriptors Applicable To Residential Areas" as shown on Table 5, page 31, of the Seminar Notes, Noise Control Plan Develoqnent, 197S, presented for the U.S. Department of 7ransportation, FAA, by Bolt, Beranek and Ne��an, Inc. QUALITATIVE DESCRIPTORS APPLICABLE TO RESIDENTIAL AREAS Threshold Speech Cortmunication O�tdoor Judgnents Exceeded Disturbance Indoors of Single Eve:it (dBA (A)) --------------------------- Maxima Windows Windows Ope� Closed _______________________________________'=____---------------- 6� just noticeable none quiet 7� moderate just noticeable generzlly acceptable 85 severe moderate noisy 95 extreme severe excessively noisy