Q. What does Sutro Tower do?
Ten television stations, three FM radio stations, and 20 wireless and mobile communications users (i.e. law enforcement agencies, taxi cabs, school buses, wireless internet, etc.) rely on Sutro Tower™ antennas to transmit signals over the air to the entire Bay Area.
Q. Why is Sutro Tower Necessary?
Over the air television reception is still used by more than 1 million people in the Bay Area who do not pay to subscribe to cable or satellite television. Over the air television and radio also provide critical local news sources during emergencies even if cable lines are down. New wireless and mobile technologies also are supported by Sutro Tower.
Q. Can Sutro Tower antennas be located elsewhere?
No. In the recently completed Environmental Impact Report, other locations were studied and found to be inadequate to serve the needs of the entire area population.
Q. Are Sutro Tower transmissions regulated?
The Federal Communications Commission (FCC) has authority over all forms of over the air transmissions. Stations must adhere to strict safety and signal clarity regulations regarding power levels, transmission frequencies and public radio frequency radiation exposure.
Q. Are Sutro Tower transmissions dangerous?
No. The radio frequency radiation exposure limits set by the FCC are 50 times lower than any level found by numerous scientific studies to have any negative effect on health. The radiation from Sutro Tower is 6% of the FCC limit at the point of maximum exposure under normal conditions. Even under unusual conditions when auxiliary antennas located lower on the tower are used, the maximum radiation level is less than 15% of the standard. Other locations throughout the area have an even lower exposure level. The levels in areas surrounding the tower are regularly measured by a licensed independent consulting engineer to insure the levels are within these limits.
Q. Does the City and County of San Francisco have any authority over Sutro Tower?
Yes. The City and County has authority over structural integrity to insure public safety in the event of earthquakes or severe storms. When the tower was originally built the City approved a Conditional Use Permit to allow the tower to be built in a residential neighborhood. The terms and conditions of this permit limit the tower to specific wireless communications uses. These terms and conditions are enforced by the San Francisco Planning Commission and the Department of Building Inspection by requiring a building permit for any addition or alteration to the tower facilities.
Q. Does the public have the ability to review and comment on Sutro Tower plans?
Yes. Whenever an application for a building permit is filed, the Planning Commission holds a public hearing where anyone can comment in person or in writing.
Q. Is the tower safe during a major earthquake?
Yes. Exhaustive structural studies have determined that the tower will withstand an earthquake at least as severe as the 1906 event. In fact, it will withstand what engineers believe is the maximum energy able to be caused by any event in the San Andreas Fault. One-third of the tower undergoes a detailed inspection each year by an independent testing laboratory approved by the City, including plates, bolts, welds, trusses, concrete and all other components. Remediation of instances of wear or rust result in like-new condition every three years. Sutro Tower has undergone several structural reinforcing projects over the years to maintain its structural integrity as engineers learn more and more about seismic events.
Top Ten Facts
1. Sutro Tower is 977 feet high, with a base elevation of 834 feet, so its highest antennas are 1,811 feet above sea level.
2. The Tower’s three legs are embedded in 15 million pounds of cement.
3. The Tower is made of 3.5 million pounds of steel.
4. The Tower opened on July 4, 1973.
5. From 1949 to 1973 there was a 588-foot tower nearby, but it did not provide a clear television signal to many parts of the Bay Area.
6. A two-person cage elevator takes workers up the Tower.
7. Emissions from the Tower are measured regularly at 200 nearby locations, and have never reached or exceeded safety standards for radio transmission.
8. Independent engineers inspect the Tower regularly to ensure safety.
9. The Tower’s colors are white and “aviation orange”.
10. The Tower is not open to the public.