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Memo to PC • • <br /> Ambient Noise Level <br /> Docket #SU-81-10 <br /> December 11, 1981 <br /> Page Two <br /> Staff does not feel that the noise level standard recommended for mining <br /> activities is appropriate using a typical ambient level of 45 dBA, the <br /> proposed standard would allow noise increases as high as: <br /> 1) 10 dBA continuous anytime during working hours <br /> 2) 20 dBA for fifteen (15) minutes of any one-hour period (L25= <br /> 65dBA) <br /> 3) 20dBA continuous during scraping operations which would occur <br /> when an area was initially being mined, even though this would <br /> be offset somewhat by the commitment to initiate mining only <br /> during winter months <br /> As described in the table on pages 3 and 4 of the staff recommendation dated <br /> November 13, 1981, expected reactions to the increases in sound levels that <br /> would be allowed by the proposed standard would include: <br /> 1) Threats of community action to vigorous community action <br /> 2) Widespread complaints, threats of legal action and appeals <br /> for government intervention <br /> 3) A perceived doubling of loudness (+10dBA) to a perceived <br /> dramatic change in loudness (+20dBA) <br /> In staff's opinion, allowing such high increases in noise levels would have <br /> a severe impact on the neighborhood and would not be compatible. <br /> Staff's analysis in the November 13th memo discussed the fact that noise <br /> from the mining would be noticeable but that it should not be allowed to <br /> cause unreasonably adverse impacts on the area. <br /> Staff feels that the following maximum noise levels from mining operations as <br /> received at the monitoring site behind 1230 Chambers Drive should be applied: <br /> L = 55 <br /> LI = 54 <br /> L50= 53 <br /> L90= 52 <br /> Since scraping operations, meaning removal of topsoil or overburden prior to <br /> beginning mining of an area, occur very infrequently, and the applicants have <br /> committed to restrict these operations to winter months, staff feels that, <br /> as proposed by the applicant, scraping operations should be exempted from <br /> the noise level standard. This should be subject to the express condition <br /> that the applicants complete the scraping operations as quickly and <br /> efficiently as possible. <br /> GRG/cld <br />