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7imbra htt :llbr <br /> p usa.180/zambralh/pruntmessage'!id-- <br /> 3sezz <br /> r <br /> i <br /> ZE117b1'd kswanson@sjgov,org <br /> i ±Font size <br /> J <br /> RE. Nighttime Truck Operations at Munn & Perkins Project <br /> From :Paul Bollard <paulb@bacnoise.com> Tue,Sep 07,2010 11:16 AM <br /> Subject.RE: Nighttime Truck operations at Munn&Perkins Project <br /> To:'Paul Bollard'<paulb@bacnoise.com>,Kevin Swanson<kswanson@sjgov.org> <br /> Cc:Mike''McGrew<mmcgrew@neumiller,com>, 'Jeff Welch{BRI-Agency Compliance}' <br /> <jeff.welch@reed,net>,christines@bacnoise.com,christines@bacnoise.com <br /> Good morning Kevin, <br /> As a follow-up to our recent communications, I am providing this e-mail to provide additional explanation pertaining to why there <br /> i are different numbers of trucks required to satisfy the 65 dB Ldn County noise standard for the 9 pm hour and hours after 10 pm. <br /> The differences in numbers of trucks has to do with the method in which Ldn is calculated. Specifically, Ldn represents a <br /> 24-hour average of noise Wth any noise events occurring during nighttime hours(10 pm to 7 am),penalized by a factor of 10 <br /> prior to averaging. As a result,each truck passby after 10 pm and before 7 am counts the same as 10 truck passbys during <br /> daytime hours(7 am—10 pm). In other words, 3 nighttime trucks are equivalent to 30 daytime trucks in the calculation of Ldn. <br /> Because the applicant is requesting permission to extend operations when necessary to 9 pm to 5 am,the'extended hours include <br /> one daytime hour(9-10 pm), and 7 nighttime hours(10 pm—5 am)_ As a result, the Ldn computed from those operations <br /> F1, <br /> depends on the number of truck trips generated during the 9-10 pm hour,and the number of trucks generated between 10 pm <br /> (^ and 5 am. <br /> p ; Since each daytime truck load counts the same at 10 nighttime loads,the 33 4oads evaluated below for the 9 pm hour would result <br /> in the same appicAmate computation of Ldn as 3.3 nighttime loads. This is why more truck trips could occur if night paving <br /> projects begin during the 9 pm hour than if they begin after 10 pm. <br /> F-1 I recognize that these computations are not intuitive,but I hope this additional explanation helps. if, homver, I have not fully <br /> clarified vdny I provided two sets of truck numbers in my earlier e-mail, please let me know and I'll try to provide additional <br /> explanation. J <br /> Sincerely, <br /> f <br /> Paul Bollard <br /> Paul Bollard,President j <br /> Institute of Noise Control Engineers(INCE),-Board Certified Member <br /> Bollard Acoustical Consultants, Inc. (BAC) <br /> 455 Alain Street, Suite 3 <br /> Newcastle, CA 95658 <br /> Office(916)663-0500 <br /> Fax(916)663-0501 <br /> Cell(916)765-4113 <br /> er <br /> Please visit BACNOISE.COM to view or download BAC Qualifications, Insurance Information, Rate Sheet, Representative Project <br /> Experience, and Staff Photos. <br /> From:Paul Bollard[Mai Ito:paulb@bacnoise.com] <br /> Sent:Tuesday,August 31,2010 1:39 PM <br /> To: 'Kevin Swanson' <br /> Cc:'McGrew,Mike'; 'Jeff Welch(BRI-Agency Compliance}'; 'christines@bacnoise.com' <br /> Subject:Nighttime Truck Operations at Munn&Perkins Project <br /> i <br /> 1 oft 09/07120104:56 PM <br />