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HomeMy WebLinkAboutEnvironanalysis revised RF Sound review 5-7-15REVIEW OF NON-IONIZING ELECTROMAGNETIC RADIATION EXPOSURE AND NOISE IMPACTS IN COMPLIANCE WITH THE CITY OF EUGENE CODE EC.9.5750 For Conditional Use Permit CU 14-3 Crossfire Church 4060 W. Amazon Drive Eugene, Oregon PREPARED FOR THE CITY OF EUGENE PLANNING AND DEVELOPMENT DEPARTMENT Prepared by Environalysis, LLC Seattle, WA REVISED May 2015 INTRODUCTION The City of Eugene Department of Planning and Development asked Environalysis, LLC to provide a review of the RF and noise emissions of a new communications facility to be located at 4060 West Amazon Drive, Eugene Oregon on land zoned as residential (R-1) and adjacent to other R-1 zones. A new 75’ tall monopole would be constructed with associated telecommunications equipment cabinets and a 50KW emergency power generator. A total of twelve (12) antennas would be added to the monopole (four antennas in each of the three sectors). The City facilitated this review by providing the following data:  Project plans from AT & T for Conditional Use Permit number 14-3  Application Package from applicant including a NIER (non-ionizing electromagnetic radiation) and an acoustic report. NOISE AND RF EMISSIONS OF THE PROJECT AT & T is proposing to construct a new 75’ tall monopole and equipment platform to be located at 4060 West Amazon Drive. This monopole would be sited on property zoned as residential (R- 1) and borders residential (R-1) land; thus an examination of potential noise impacts is necessary. The new antennas would be centered at 71 feet above grade. There will be a total of twelve (12) antennas installed on the monopole (designed to appear as a tree and known as a “monopine”). Communications equipment cabinets will be housed in a temperature-controlled shelter. A 50 kW diesel-powered emergency generator will be installed as part of this project PROJECT IMPACTS The City’s maximum permissible property-line noise standard of 45 dBA applies to this site as it adjoins residential zones. The overall sound pressure rating of the telecommunications equipment to be installed is 72 dBA measured at a distance of 5 feet. The nearest residential property lines are 70 feet to the west and 200 feet to the south. The resulting noise impacts are under the City’s noise ordinance level of 45 dBA but not less than the 35 dBA agreed to by the City for the south property line as part of the Conditional Use Permit process. The installation of low- noise blower options on the two air conditioning units will enable compliance with the 35 dBA limit. The emergency generator will be operated during power outages and for a monthly 10-minute test) and will cause noise impacts greater than the City’s Ordinance. The proposed 9 foot high noise wall and other mitigation measures (such as, insulating the emergency generator shed and installing a highly effective exhaust stack muffler, an insulated air intake hood and air discharge louver) will reduce them to nearly the 45 dBA standard. However, in order to reduce the generator’s noise impacts to within the City Ordinance the Proponent’s acoustic consultants issued a revised report (April 20, 2015) which incorporated the following changes:  Adding an insulated elbow for the air discharge that will direct the warm air discharge from the generator room downwards towards the ground. For the best results the ground under the elbow should not be a hard reflective surface such as asphalt or concrete; but should be lawn or landscaping. The noise attenuation for this elbow is supported by data from ASHRAE for the insulated elbows of the appropriate dimensions.  The noise attenuation for the GT-201-5100 critical grade exhaust muffler was increased from 30 dBA to 35 dBA. An examination of data from GT for this model of muffler indicates that 35 dBA is the more accurate attenuation factor.  A change was made in how noise attenuation factors were assigned for the air intake noise that would be experienced at the nearest residential property to the west. The “building factor” was reduced by 7 dBA and this same amount was added to the “noise control” category. This change reflects the fact that the noise reduction from the air intake plenum belongs more properly in the “noise control” category than in the “building factor” category but has no effect upon the overall noise impacts.  The revised report corrected a misprint for the” Building factor” noise attenuation for air intake impacts at the south residential property line. The figure of -10 dBA should not have been in the table. The dBA impacts remain unchanged as the total for all noise attenuation (Build Factor + Noise Control) does not change (it is -17 dBA in both reports).  One error does remain in the revised “Receiving Property-South” table: The dBA impact at the south residential property for exhaust noise should have been calculated as 31 dBA not the 36 dBA shown in the table. However, due to the fact that noise levels add logarithmically there will be no change in the total impact level of 45 dBA. The emergency generator, with the additional mitigation measure of an insulated hood for the air intake will meet the City’s 45 dBA standard. The applicant provided calculations of RF emissions that would be received by a person at ground level. Their calculations follow standard formulas. The RF power density calculations performed indicate the maximum power exposure for a person standing at ground level and indicate that the maximum power density for a person would be less than 1.3% of the FCC standards for the general public. The results are consistent with the reported output power of the antennas. CONCLUSIONS The information in the applicant’s proposal is sufficient to determine that the NIER impacts of the project fall well within Federal and City regulatory limits. The applicant detailed noise mitigation measures that will enable the proposal to meet the City’s noise ordinance and stricter limits agreed to as part of the CUP process. No additional conditions need to be applied to mitigate either the project’s sound pressure levels or its NIER emissions.