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SF04552A RF Exposure Study 05202022T-Mobile West LLC • Base Station No. SF04552A 20401 Stevens Creek Boulevard • Cupertino, California Statement of Hammett & Edison, Inc., Consulting Engineers The firm of Hammett & Edison, Inc., Consulting Engineers, has been retained by T-Mobile West LLC, a personal wireless telecommunications carrier, to evaluate proposed modifications to its existing base station (Site No. SF04552A) located at 20401 Stevens Creek Boulevard in Cupertino, California, for compliance with appropriate guidelines limiting human exposure to radio frequency ("RF") electromagnetic fields. Executive Summary T-Mobile proposes to add directional panel antennas on short poles above the roof of the two-story commercial building located at 20401 Stevens Creek Boulevard in Cupertino. The proposed operation will comply with the FCC guidelines limiting public exposure to RF energy; certain mitigation measures are recommended to comply with FCC occupational guidelines. 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 DoD-Band 3,450 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 HEHAMMETT & EDISON, INC. CONSULTING ENGINEERS S5A3 SAN FRANCISco ,�z0zz Page 1 of 4 T-Mobile West LLC • Base Station No. SF04552A 20401 Stevens Creek Boulevard • Cupertino, California 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 passive 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 T-Mobile, including construction drawings by Precision Design and Drafting, Inc., dated March 7, 2022, that carrier presently has twelve directional panel antennas — three Ericsson Model AIR6449, three Ericsson Model AIR1641, three RFS Model APXVAALL24 43- U-NA20, and three Ericsson Model AIR5121 — installed on short poles above the roof of the two-story commercial building located at 20401 Stevens Creek Boulevard in Cupertino, mounted at effective heights of about 49, 47'/2, 46'/2, and 49 feet above ground, respectively, 14, 12'/2, 11'/z, and 14 feet above the roof, respectively. It is proposed to install six Ericsson directional panel antennas — three additional Model AIR6449 and three Model AIR6419 — below the existing antennas at an effective height of about 43 feet above ground, 8 feet above the roof. The Ericsson Model AIR6449 antennas would employ up to 19' downtilt, the Ericsson Model 1641 and 5121 antennas would employ up to 12' and 15' downtilt, respectively, and the RFS antennas would employ 2° downtilt. The antennas would be oriented in identical groups of six toward 0°T, 120°T, and 240°T, to provide service in all directions. HEHAMMETT & EDISON, INC. CONSULTING ENGINEERS S5A3 SAN FRANCISco ,�z0zz Page 2 of 4 T-Mobile West LLC • Base Station No. SF04552A 20401 Stevens Creek Boulevard • Cupertino, California The maximum effective radiated powers proposed by T-Mobile in the principal directions are: Maximum Effective Radiated Power Band 0°T 1200T 2400T 28 GHz 243 243 243 watts C-Band* 50,600 25,300 25,300 DoD-Band* 43,550 21,775 21,775 BRS 29,660 29,660 14,830 AWS 9,850 9,850 9,850 PCs 13,630 13,630 13,630 700 MHz 880 880 880 600 MHz 3,380 3,380 3,380 151,793 104,718 89,888 watts Study Results For a person anywhere at ground, the maximum RF exposure level due to the proposed T-Mobile operation is calculated to be 0.40 mW/cm2, which is 40% of the applicable public exposure limit. The maximum calculated level at the roof of any nearby buildings is 88% of the public exposure limit. The maximum calculated level at any nearby residence$ is 12% 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. Levels are calculated to exceed the applicable public exposure limit on the roof of the subject building and at five tall trees nearby. Recommended Mitigation Measures It is recommended that the roof access hatch be kept locked, so that the T-Mobile antennas are not accessible to unauthorized persons. To prevent exposures in excess of the FCC guidelines, it is recommended that appropriate RF safety training, to include review of personal monitor use, review of lockout/tagout procedures, and review of the information in Figure 3, be provided to all authorized personnel who have access to the roof or to the nearby trees, including employees and contractors of T-Mobile and of the property owner. No work in the yellow -shaded areas, such as might occur during certain maintenance activities, should be allowed while the base station is in operation, unless other measures can be demonstrated to ensure that occupational protection requirements are met. It is recommended that boundary lines be marked on the roof with blue and yellow paint to identify areas where exposure levels are calculated to exceed the public and occupational FCC limits, respectively, as shown in Figure 3. It is recommended that T-Mobile coordinate with the landlord to arrange a shut -down of the base station prior to any work in the trees above 23 feet. It is recommended that * The manufacturer reports that the antenna transmits 75% of the time in this band; this factor is incorporated into the calculations. The tall single -story retail mall to the northeast. $ Located at least 225 feet away, based on photographs from Google Maps. HEHAMMETT & EDISON, INC. CONSULTING ENGINEERS S5A3 SAN FRANCISco ,�z0zz Page 3 of 4 T-Mobile West LLC • Base Station No. SF04552A 20401 Stevens Creek Boulevard • Cupertino, California explanatory signs§ be posted at the roof access hatch, at the boundary lines, and at the antennas, as shown in Figure 3, readily visible from any angle of approach to persons who might need to work within that distance. Conclusion Based on the information and analysis above, it is the undersigned's professional opinion that the proposed operation of the T-Mobile West LLC base station located at 20401 Stevens Creek Boulevard in Cupertino, California, can comply with the prevailing standards for limiting human exposure to radio frequency energy and, therefore, need 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. Locking the roof access hatch is recommended to establish compliance with public exposure limits; training authorized personnel, marking roof areas, and posting explanatory signs are recommended to establish compliance with occupational exposure limits. Authorship The undersigned author of this statement is a qualified Professional Engineer, holding California Registration Nos. E-13026 and M-20676, which expire on June 30, 2023. This work has been carried out 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. QprOF E:S.S/p, c 3 E-13026 M -20676 Ex-6-30-2023 May 20, 2022 William F. Ha ett, P.E. 707/996-5200 § Signs should comply with FCC Rules 47 CFR § 1.1307(b)(4)(vi) color, symbol, and content recommendations. HEHAMMETT & EDISON, INC. CONSULTING ENGINEERS S5A3 SAN FRANCISCO ©2022 Page 4 of 4 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 and approved as American National Standard ANSI/IEEE C95.1-2006, "Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to 300 GHz," includes similar limits. These limits apply for continuous exposures from all sources and are intended to provide a prudent margin of safety for all persons, regardless of age, gender, size, or health. 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 Applicable Range (MHz) 0.3 — 1.34 1.34 — 3.0 3.0 — 30 30 — 300 300— 1,500 1,500 — 100,000 1000 100 10 1 0.1 Electromagnetic Fields (f is freauencv of emission in MHz Electric Magnetic Equivalent Far -Field Field Strength Field Strength Power Density (V/m) (A/m) (mW/CM2) 614 614 1.63 1.63 100 100 614 823.8/f 1.63 2.19/f 100 180/f2 1842/ f 823.8/f 4.89/ f 2.19/f 900/ f z 180/f z 61.4 27.5 0.163 0.0729 1.0 0.2 3.54�f 1.59ff 4f/106 Tf1238 f/300 f11500 137 61.4 0.364 0.163 5.0 1.0 Occupational Exposure !/ PCS ♦ FM Public Exposure 0.1 1 10 100 103 104 105 Frequency (MHz) Higher levels are allowed for short periods of time, such that total exposure levels averaged over six or thirty minutes, for occupational or public settings, respectively, do not exceed the limits, and higher levels also are allowed for exposures to small areas, such that the spatially averaged levels do not exceed the limits. However, neither of these allowances is incorporated in the conservative calculation formulas in the FCC Office of Engineering and Technology Bulletin No. 65 (August 1997) for projecting field levels. Hammett & Edison has incorporated those formulas in a computer program capable of calculating, at thousands of locations on an arbitrary grid, the total expected power density from any number of individual radio frequency sources. The program allows for the inclusion of uneven terrain in the vicinity, as well as any number of nearby buildings of varying heights, to obtain more accurate projections. KEHAMMETT & EDISON, INC. FCC Guidelines CONSULTING ENGINEERS SAN FRANCISCO ©2022 Figure 1 RFE.CALCTM Calculation Methodology Assessment by Calculation of Compliance with FCC Exposure Guidelines 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: power density S = 2.56x 1.64x 100xRFF2xERP 4xaxD2 in mW/cm2 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": power density S = esw x �c x D Xhnin mW/cm2 where Pnet = net power input to antenna, in watts, OBW = 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. HEHAMMETT & EDISON, INC. CONSULTING ENGINEERS Calculation Methodology SAN FRANCISCO ©2022 Figure 2 T-Mobile West LLC • Base Station No. SF04552A 20401 Stevens Creek Boulevard • Cupertino, California Calculated RF Exposure Levels on Roof Recommended Mitigation Measures • Lock roof access hatch • Mark boundaries as shown • Post explanatory signs T-Mobile • Provide training / antenna groups Notes: See text. Base image from Google Maps. Calculations performed according to OET Bulletin 65, August 1997 Legend'' Less Than Exceeds Exceeds Exceeds lOx Public Public Occupational Occupational Shaded color blank ■ ■ Boundary marking N/A Sign type N/A B - Blue Y- Yellow Q - Orange NOTICE CAUTION WARNING HAMMETT & EDISON, INC. CONSULTING ENGINEERS HESAN FRANCISCO ©2022 at roof ss hatch FEET 25 0 25 50 S5A3 Figure 3