1. Summary
Sutro Tower is an existing 977-foot tall steel structure/tower which includes antennas for ten television stations and four FM radio stations. Visible from most areas of San Francisco, the Tower is located on ... the east peak of Mount Sutro in central San Francisco.
This Draft EIR examines the potential environmental effects of a proposed project to install Digital Television (DTV) antennas onto Sutro Tower. A new DTV antenna system able to accommodate the 10 television stations ... would be attached to a new 125 foot long beam, which would extend down from a location near the top of Sutro Tower.
The current FCC deadline for beginning DTV signal broadcasts in the Bay Area is October, 1998. ... If the proposed project is approved there would be an overlap period tentatively set for 9 years during which both DTV and the existing NTSC television signals would be broadcast from Sutro Tower.
The main area of controversy surrounding the proposed project involves the potential for adverse health effects from radio frequency radiation (RFR). ... During the period of overlap, when both DTV and NTSC signals would be broadcast, RFR would increase above existing levels. After the NTSC signal broadcasts are terminated, RFR would drop below existing levels.
The proposed project would emit electromagnetic waves in the frequency range of 500-734 megahertz. These wavelengths are millions of times shorter than those generated by electric power lines. Accordingly, the interactions with biological bodies differ between exposure to RFR and exposure to electric and magnetic fields generated by power line frequencies.
A Technical Report on the Biological Effects of Radiofrequency Radiation and Possible Health Effects of RFR on Humans from Sutro Tower DTV Broadcasts has been prepared and is included as Appendix B to the EIR.
... Some past researchers have published reports concluding that there is the potential for adverse health effects from RFR. In reviewing these past studies, the technical report for this EIR concludes that either 1) the adverse effects identified were the result of a thermal effect (a hazardous increase in body or cell temperature) which resulted from RFR levels greater than those that would be generated by the proposed project; or 2) taken collectively, there is little or no reliable scientific evidence to indicate that the proposed project would have adverse health effects ... from RFR levels at or below those permitted in the FCC 96 Guidelines.
The proposed project, during the period of overlapping signal transmission, would emit RFR up to a maximum of about 14 percent of the levels permitted by the FCC 96 Guidelines.
While concluding that the results of many investigations provides confidence that exposure to RFR at or below the levels prescribe din the FCC 96 Guidelines is unlikely to be harmful, the technical report acknowledges that some of the mechanisms of interaction of RFR with various biological entities are not fully understood, and life processes are complex. ... the substantial weight of reliable scientific evidence indicates that there would not be any adverse health effects from the proposed project.
The 1992 ANSI/IEEE Guidelines first established a threshold level of RFR exposure at which it was generally agreed that adverse health effects, including thermal effects, could occur. A safety factor of 50 times (i.e., divide the lowest established level known to cause an adverse effect by 50) was established for uncontrolled environments (public exposures). These guidelines were subsequently adopted into the FCC 96 Guidelines.
The closest residence is about 250 feet away from the base of the tower, and over 800 feet from the closest antenna. ... The highest measured and calculated levels of existing public exposure to RFR from Sutro Tower is at Farview Court, approximately on e block from the tower. The calculated level of 0.025 milliwatts per square centimeter (mW/cm2) is at about 12.7 percent of the FCC 96 Guidelines.
With the addition of DTV antennas, the maximum exposures from broadcast emissions from the proposed project at the closest sensitive receptor would be at about 0.029 mW/cm2 or 14.3 percent of the allowable maximum...
In the San Francisco Bay Area, three of the highest sites are currently used for television broadcasting: Sutro Tower, San Bruno Mountain, and Mount Diablo. ... Signals broadcast from Sutro Tower, San Bruno Mountain, and Mount Diablo are not interchangeable because of their distance from each other and the cities of license.
New DTV channel allotment rules specify that each station's DTV transmitting antenna location must be within 5 kilometers of the existing NTSC transmitter sites (FCC Rules, Rules, Section 73.622(d)(1), 47 C.F.R. Section 73.622). Exemptions to this rule may be used for alternatives located farther than 5 kilometers, if an engineering study can show that there will be no additional interference to any other stations.
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