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HomeMy WebLinkAboutCorrespondence APPLICANT 3/19/2004 ~ ,. . " C 0 U S T I tA L I-N-H RECRIVRD MAR 1 9 2004 Mike EvansBY: Land Planning Consultant 1071 Harlow Rd Springfield, OR 97477 ea,.rthur M. Noxon, PE. ACOUSTIC, NOISE AND VIBRATION CONTROL engineering survey and ctnidysfs. project design and management Date: 3/3/2004 RE: Community Noise Impact from Proposed Mountain Gate Crushing Operation The plan for developing the Mountain Gate Project includes converting the rock from the mountain into base material and gravel for roads and residential sites. This will requirll blasting, hauling and crushing operations. This noise study concentrates on the crushing aspect of the noise generated during the rock handling part of the project. It should be mentioned here that "site work" is exempt from DEQ noise regulation standards. The mining, crushing and hauling of rock on this housing project site appears to meet the temporary condition of "site work" and the noise should be exempt from DEQ regulation. Crusher Noise Crusher noise at a distance has been measured many times. Typical noise levels will be about 66 dB;A at 1200 feet, with an open line of sight into the crusher operation. The present plan calls for two crushing sites. Site A will be located in the future detention pond area and is about 350 feet from the nearest house, located 40 feet lower and to the southwest. Site B will be up on top of the mountain and is located just over 900 feet from the nearest house, some 220 feet lower, again to the southwest. Noise from rock crushers is a well studied and documented topic. Line of sight noise from a typical crusher operation registers 66 dB,A at 1200 feet. At this distance, the lateral expanse of the crusher operation is relatively small and the sound can be considered to bc coming Irom a point source. Site A The direct line of sight noise impact on houses near the Site A crusher will be 79 dB,A. However, a very large berm is planned to be positioned between the crusher and the houses to the southwest. This berm will rise well above the top of the crusher and block the line of sight between all parts of the crusher line and any houses below. ". ~~~. Date Received: ;rlCf-O* Planner: J r 6T 2fX~GJ~ 3690 County Farm Rd, - Eugene, OR 97408 - Ph: 54t-343-9727 - Fax: 541-343-9245 ';'"' ~ " . . A 15 dB noise berm for an elevated noise source here should block the line of sight between the top of the crusher and the upstairs windows of the nearby houses below by about 19 feet. The berm is called "temporary stockpile" and it's peak is located about 180 feet from the crusher. The peak of the berm should be set at Elevation 629 feet if the top of the crusher is located at Elevation 623 feet to achieve a 15 dB attenuation from noise out of the top of the crusher. Noise from crusher A should be impacting the nearest houses at a noise level of 64 dB,A. SiteB Crusher site B is located in a cut that will later become a road, on top of the mountain. The distance between the crusher and the nearest houses is over 900' and the ground slopes down some 220'. Due to the distance, the line of sight noise levels from the crusher should be in the range of 69 dB,A. However it is in a cut that nearly blocks the line of sight to the houses, and that will reduce the noise by about 5 dB.' Further, because the ground slopes away significantly, there is an added expansion factor of about I dB additional attenuation. This puts the projected noise at the nearest houses to be around 63 dB ,A. Often in longer range noise paths such as this, atmospheric attenuation is included in the calculation, in this case about -I dB. Generally noise from the crusher atop the mountain in a cut that essentially just blocks the line of sight to the nearest houses, the crusher noise should be expected in the range of 63 dB,A. Conclusion Noise from either crusher operation, Site A or Site B should impact the nearest houses no greater than the 63 to 64 dB,A range, possibly. a few dB less. Although this is well above the DEQ upper limit for continuous industrial noise, 55 dB,A, the crushing operation'is temporary and only being used for site development and is a DEQ exempt noise source a;;J~ Arthur Noxon, PE Acoustical Engineer ".....,....,..-. .