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HomeMy WebLinkAboutUP23-0007_9.RF StudyVertical Bridge • Site No. US-CA-5447 T-Mobile West LLC • Proposed Base Station No. SC60520A 4825 Foothill Boulevard • Oroville, California D6YV Page 1 of 4 ©2023 Statement of Hammett & Edison, Inc., Consulting Engineers The firm of Hammett & Edison, Inc., Consulting Engineers, has been retained by Vertical Bridge, a wireless telecommunications facilities provider, to evaluate the T-Mobile West LLC base station (Site No. SC60520A) proposed to be located at 4825 Foothill Boulevard in Butte County near Oroville, California, for compliance with appropriate guidelines limiting human exposure to radio frequency (“RF”) electromagnetic fields. Executive Summary T-Mobile proposes to install directional panel antennas on a tall pole configured to resemble a pine tree, to be sited at 4825 Foothill Boulevard near Oroville. The proposed operation will comply with the FCC guidelines limiting public exposure to RF energy. Prevailing Exposure Standard The U.S. Congress requires that the Federal Communications Commission (“FCC”) evaluate its actions for possible significant impact on the environment. A summary of the FCC’s exposure limits is shown in Figure 1. These limits apply for continuous exposures and are intended to provide a prudent margin of safety for all persons, regardless of age, gender, size, or health. The most restrictive limit for exposures of unlimited duration at several wireless service bands are as follows: Transmit “Uncontrolled” Occupational Limit Wireless Service Band Frequency Public Limit (5 times Public) Microwave (point-to-point) 1–80 GHz 1.0 mW/cm2 5.0 mW/cm2 Millimeter-wave 24–47 1.0 5.0 Part 15 (WiFi & other unlicensed) 2–6 1.0 5.0 C-Band 3,700 MHz 1.0 5.0 CBRS (Citizens Broadband Radio) 3,550 1.0 5.0 BRS (Broadband Radio) 2,490 1.0 5.0 WCS (Wireless Communication) 2,305 1.0 5.0 AWS (Advanced Wireless) 2,110 1.0 5.0 PCS (Personal Communication) 1,930 1.0 5.0 Cellular 869 0.58 2.9 SMR (Specialized Mobile Radio) 854 0.57 2.85 700 MHz 716 0.48 2.4 600 MHz 617 0.41 2.05 [most restrictive frequency range] 30–300 0.20 1.0 Vertical Bridge • Site No. US-CA-5447 T-Mobile West LLC • Proposed Base Station No. SC60520A 4825 Foothill Boulevard • Oroville, California D6YV Page 2 of 4 ©2023 General Facility Requirements Base stations typically consist of two distinct parts: the electronic transceivers (also called “radios”) that are connected to the traditional wired telephone lines, and the antennas that send the wireless signals created by the radios out to be received by individual subscriber units. The transceivers are often located at ground level and are connected to the antennas by coaxial cables. Because of the short wavelength of the frequencies assigned by the FCC for wireless services, the antennas require line-of- sight paths for their signals to propagate well and so are installed at some height above ground. The antennas are designed to concentrate their energy toward the horizon, with very little energy wasted toward the sky or the ground. This means that it is generally not possible for exposure conditions to approach the maximum permissible exposure limits without being physically very near the antennas. Computer Modeling Method The FCC provides direction for determining compliance in its Office of Engineering and Technology Bulletin No. 65, “Evaluating Compliance with FCC-Specified Guidelines for Human Exposure to Radio Frequency Radiation,” dated August 1997. Figure 2 describes the calculation methodologies, reflecting the facts that a directional antenna’s radiation pattern is not fully formed at locations very close by (the “near-field” effect) and that at greater distances the power level from an energy source decreases with the square of the distance from it (the “inverse square law”). This methodology is an industry standard for evaluating RF exposure conditions and has been demonstrated through numerous field tests to be a conservative prediction of exposure levels. Site and Facility Description Based upon information provided by Vertical Bridge, including drawings by Assurance Development, dated May 17, 2023, T-Mobile proposes to install twelve directional panel antennas – three CommScope Model FFVV-65C-R3-V1, three Ericsson Model AIR6419, and six* antennas for future operation – on a 95-foot steel pole, configured to resemble a pine tree,† to be sited about 200 feet to the northwest of the single-story residence located at 4825 Foothill Boulevard in unincorporated Butte County, about 4 miles southeast of Oroville. The CommScope and Ericsson antennas would employ up to 13° and up to 19° downtilt, respectively, would be mounted at an effective height of about 91 feet above ground, and would be oriented in three identical groups of four at about 120° spacing, to provide service in all directions. The maximum effective radiated power in any direction would be 30,350 watts, * It is recommended that the RF exposure conditions be re-evaluated for compliance with FCC limits at such time as these antennas are to be put into service. † Foliage atop the pole puts the overall height at about 100 feet. Vertical Bridge • Site No. US-CA-5447 T-Mobile West LLC • Proposed Base Station No. SC60520A 4825 Foothill Boulevard • Oroville, California D6YV Page 3 of 4 ©2023 representing simultaneous operation at 14,230 watts for BRS,‡ 6,200 watts for AWS, 5,430 watts for PCS, 950 watts for 700 MHz, and 3,540 watts for 600 MHz service. Also proposed to be located on the pole, at an effective height of about 86 feet above ground, is a microwave “dish” antenna, for interconnection of this site with others in the T-Mobile network. There are reported no other wireless telecommunications base stations at the site or nearby. Study Results For a person anywhere at ground, the maximum RF exposure level due to the proposed T-Mobile operation, including the contribution of the microwave dish, is calculated to be 0.050 mW/cm2, which is 6.5% of the applicable public exposure limit. The maximum calculated level at the second-floor elevation of the nearby residence is 8.3% of the public exposure limit. It should be noted that these results include several “worst-case” assumptions and therefore are expected to overstate actual power density levels from the proposed operation. No Recommended Mitigation Measures Due to their mounting location and height, the T-Mobile antennas would not be accessible to unauthorized persons, and so no measures are necessary to comply with the FCC public exposure guidelines. It is presumed that T-Mobile will, as an FCC licensee, take adequate steps to ensure that its employees or contractors receive appropriate training and comply with FCC occupational exposure guidelines whenever work is required near the antennas themselves. Conclusion Based on the information and analysis above, it is the undersigned’s professional opinion that operation of the base station proposed by T-Mobile West LLC at 4825 Foothill Boulevard in Butte County near Oroville, California, will comply with the prevailing standards for limiting public exposure to radio frequency energy and, therefore, will not for this reason cause a significant impact on the environment. The highest calculated level in publicly accessible areas is much less than the prevailing standards allow for exposures of unlimited duration. This finding is consistent with measurements of actual exposure conditions taken at other operating base stations. ‡ T-Mobile reports maximum effective radiated power in this band of 59,310 watts, to which a duty cycle of 75% is applied; a statistical factor of 32% is also included, to account for spatial distribution of served users, based on the United Nations International Telecommunication Union ITU-T Series K, Supplement 16, dated May 20, 2019. Vertical Bridge • Site No. US-CA-5447 T-Mobile West LLC • Proposed Base Station No. SC60520A 4825 Foothill Boulevard • Oroville, California D6YV Page 4 of 4 ©2023 Authorship The undersigned author of this statement is a qualified Professional Engineer, holding California Registration No. E-23220, which expires on June 30, 2024. This work has been carried out by him or under his direction, and all statements are true and correct of his own knowledge except, where noted, when data has been supplied by others, which data he believes to be correct. Manas S. Reddy, P.E. 707/996-5200 July 17, 2023 FCC Guidelines Figure 1 1000 100 10 1 0.1 0.1 1 10 100 103 104 105 Occupational Exposure Public Exposure PCS CellFM PowerDensity(mW/cm2)FCC Radio Frequency Protection Guide The U.S. Congress required (1996 Telecom Act) the Federal Communications Commission (“FCC”) to adopt a nationwide human exposure standard to ensure that its licensees do not, cumulatively, have a significant impact on the environment. The FCC adopted the limits from Report No. 86, “Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields,” published in 1986 by the Congressionally chartered National Council on Radiation Protection and Measurements (“NCRP”). Separate limits apply for occupational and public exposure conditions, with the latter limits generally five times more restrictive. The more recent standard, developed by the Institute of Electrical and Electronics Engineers IEEE C95.1-, “SafetyLevels with Respect to Human Exposure to &MFDUSJD .BHOFUJD BOE Electromagnetic Fields, )[ to300 GHz,” includes similar limits. These limits apply for continuous exposures from all sources andare intended to provide a prudent margin of safety for all persons, regardless of age, gender, size, orhealth. As shown in the table and chart below, separate limits apply for occupational and public exposure conditions, with the latter limits (in italics and/or dashed) up to five times more restrictive: Frequency Electromagnetic Fields (f is frequency of emission in MHz) Applicable Range (MHz) Electric Field Strength (V/m) Magnetic Field Strength (A/m) Equivalent Far-Field Power Density (mW/cm2) 0.3 – 1.34 614 614 1.63 1.63 100 100 1.34 – 3.0 614 823.8/ f 1.63 2.19/ f 100 180/ f2 3.0 – 30 1842/ f 823.8/ f 4.89/ f 2.19/ f 900/ f2 180/ f2 30 – 300 61.4 27.5 0.163 0.0729 1.0 0.2 300 – 1,500 3.54 f 1.59 f f /106 f /238 f/300 f/1500 1,500 – 100,000 137 61.4 0.364 0.163 5.0 1.0 Frequency (MHz) +LJKHUOHYHOVDUHDOORZHGIRUVKRUWSHULRGVRIWLPHVXFKWKDWWRWDOH[SRVXUHOHYHOVDYHUDJHGRYHUVL[ RU WKLUW\ PLQXWHV IRU RFFXSDWLRQDO RU SXEOLF VHWWLQJV UHVSHFWLYHO\ GR QRW H[FHHGWKH OLPLWV DQG KLJKHU OHYHOV DOVR DUH DOORZHG IRU H[SRVXUHV WR VPDOO DUHDV VXFK WKDW WKHVSDWLDOO\ DYHUDJHG OHYHOV GR QRW H[FHHG WKH OLPLWV +DPPHWW  (GLVRQ KDV LQFRUSRUDWHGFRQVHUYDWLYH FDOFXODWLRQ IRUPXODV LQ WKH )&& 2IILFH RI (QJLQHHULQJ DQG 7HFKQRORJ\%XOOHWLQ 1R  $XJXVW   IRUSURMHFWLQJ ILHOG OHYHOVLQ D FRPSXWHU SURJUDP FDSDEOH RIFDOFXODWLQJ DW WKRXVDQGV RI ORFDWLRQV RQ DQDUELWUDU\ JULG WKH WRWDOH[SHFWHG SRZHU GHQVLW\IURP DQ\ QXPEHU RI LQGLYLGXDO UDGLR IUHTXHQF\ VRXUFHV  7KH SURJUDP DOORZV IRU WKHLQFOXVLRQ RIXQHYHQ WHUUDLQ LQ WKH YLFLQLW\ DV ZHOO DV DQ\QXPEHURIQHDUE\EXLOGLQJVRIYDU\LQJKHLJKWVWRREWDLQPRUHDFFXUDWHSURMHFWLRQV ©3 RFE.CALCTM Calculation Methodology Assessment by Calculation of Compliance with FCC Exposure Guidelines Calculation Methodology Figure 2 ©2023 180 θBW × 0.1× Pnet π × D × h 0.1 x 16 x n x P x h2 0.1×16 × η × Pnet π × h2 net BW 180 0.1 x Pnetx θ 180 θBW × 0.1× Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180 θBW × 0.1× Pnet π × D × hS = qBW Hammett & Edison has incorporated the FCC Office of Engineering and Technology Bulletin No. 65 (“OET-65”) formulas (see Figure 1) in a computer program that calculates, at millions of locations on a grid, the total expected power density from any number of individual radio frequency sources. The program uses the specific antenna patterns from the manufacturers and allows for the inclusion of uneven terrain in the vicinity, as well as any number of nearby buildings of varying heights, to obtain accurate projections of RF exposure levels. The program can account for spatial-averaging when antenna patterns are sufficiently narrow, and time- averaging is typically considered when operation is in single-frequency bands, which require time-sharing between the base station and the subscriber devices. OET-65 provides this formula for calculating power density in the far-field from an individual RF source: in mW/cm2power density where ERP = total Effective Radiated Power (all polarizations), in kilowatts, RFF = three-dimensional relative field factor toward point of calculation, and D = distance from antenna effective height to point of calculation, in meters. The factor of 2.56 accounts for the increase in power density due to reflections, assuming a reflection coefficient of 1.6 (1.6 x 1.6 = 2.56). This factor is typically used for all sources unless specific information from FCC filings by the manufacturer indicate that a different reflection coefficient would apply. The factor of 1.64 is the gain of a half-wave dipole relative to an isotropic radiator. The factor of 100 in the numerator converts to the desired units of power density. Because antennas are not true “point sources,” their signal patterns may not be fully formed at close distances and so exposure levels may be lower than otherwise calculated by the formula above. OET-65 recommends the cylindrical model formula below to account for this “near-field effect”: in mW/cm2 power density S = where Pnet = net power input to antenna, in watts, = half-power beamwidth of antenna, in degrees, D = distance from antenna effective height to point of calculation, in meters, and h = aperture height of antenna, in meters. The factor of 0.1 in the numerator converts to the desired units of power density. OET-65 confirms that the “crossover” point between the near- and far-field regions is best determined by finding where the calculations coincide from the two different formulas, and the program uses both formulas to calculate power density. 180 θBW × 0.1× Pnet π × D × h 0.1 x 16 x n x P x h2 0.1× 16 × η × Pnet π × h2 net BW 180 0.1 x Pnetx θ 180 θBW × 0.1× Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180 θBW × 0.1× Pnet π × D × hS = qBW 180 θBW × 0.1× Pnet π × D ×h 0.1 x 16 x n x P x h2 0.1× 16 × η × Pnet π × h2 net BW 180 0.1 x Pnetx0 180 θBW × 0.1× Pnet π × D × hx D x h 2.56 x 1.64 x 100 x RFF2 x ERP 4 x x D2 180 θBW × 0.1× Pnet π × D × hS =