108-G. Supplemental Response Letter by Hammett & Edison.pdfATTACHMENT G
li�EHAMMETT & EDISON, INC.
CONSULTING ENGINEERS
BROADCAST & WIIZELESS
BY E-MAIL COLINJ@CUPERTINO.ORG
October 26, 2010
Mr. Colin Jung, AICP
Senior Planner
City of Cupertino
10300 Torre Avenue
Cupertino, California 95014-3255
Re: Appeal of DIR-2010-28
Dear Mr. Jung:
WiLLiANtF. HAmmm, P.E.
DANE E. ERicKsEN, P.E.
STANLEY SALEK, P.E.
MARKD. NEUMANN, P.E.
RoBERTP. SMITH, JR.
RA)AT MATxaR, P.E.
IERNANDo D1zoN
KENT A. Sw1sHER
IvETTA KI IENOKH
ROBERTL. HAMMETT, P.E.
1920 2002
EDwARD EmsoN, P.E.
1920 2009
This letter provides responses to the several statements you summarized from the appeal of the
T-Mobile base station to be located at 11371 Bubb Road in Cupertino. Some of the statements
are compound, and I have tried to address the individual points succinctly, drawing specific
information where appropriate from our report dated July 28, 2010. Please let me know if
further elaboration on any of the points would be helpful.
No.1: Antenna with a maximum ERP of 360 watts is not a microcell, but a high
power antenna.
Response: This is a matter of semantics -- not a technical question. Generally, a base
station with an effective radiated power above 1,000 watts would be a "macro' site and
one under 1,000 watts would be a "micro' site, but that descriptive term has no direct
bearing on its compliance with the FCC guidelines limiting human exposure. That is,
whatever a base station is called, it has to comply with the same federal limits.
No. 2a: Federal safety standard cited by applicant does not apply to this project
because of the hilly topography and dense population. Cited standard is for an
average slow fading, flatpropagation environment.
Response: The FCC standard cited in our report is NOT based on "an average slow -
fading, flat propagation environment," nor on any other propagation assumption. The
standard sets a "Maximum Permissible Exposure" (MPE) level, which applies wherever
people might be. Certainly, the exposure conditions from a radio source would be lower
if the energy has to pass over intervening terrain, but for the purposes of our study, we
assumed that the signal has a clear line -of -sight to every location where a person might
be: indoors, outdoors, or behind a hill.
Web: www.h-e.com • bhammettGh-e.com
Delivery: 470 Third Street West • Sonoma, California 95476
Telephone: 707/996-5200 San Francisco 214/559-5200 Dallas • 202/396-5206 D.C. • 707/996.5280 Fax
Mr. Jung, page 2
October 26, 2010
No. 2b: Exposure to several hours of such radio frequency energy (540mWineter) can
cause harmful problems for children, especially those b years and under
(based on the radio health analytical model published in the 2004 World
Wireless Congress in San Francisco).
Response: There are innumerable studies of the effects of exposure to radio frequency
energy, presumably including the one mentioned above that uses (based on its title)
analytical models. Such studies are considered by the standard -setting bodies in this
country and abroad when they establish safety standards, and studies that are published
in peer -reviewed journals and whose results have been replicated carry the most
scientific weight. In the judgment of those bodies, the current standard incorporates a
margin of safety for all persons, whether old or young, large or small, sick or infirm.
No. 3: Because of the hilly terrain to the west combined with the multi -story homes,
the FCC safety limit cannot be met unless the antennas are over 100 feet away
for residents living within 500 feet.
Response: Distance alone is not the determining factor for meeting the FCC limit, but
it is certainly an important factor, as the radio frequency power falls off by the square of
the distance; this is "the inverse square law" from basic physics. Also from basic
physics is the formula for calculating power density, used by the FCC and by us, as
described in Figure 2 of our report (and attached here, too). For the 360 watts proposed
by T-Mobile, the power density has already fallen below the WE level at a distance of
12 feet in front of the antennas — not 100 feet and certainly not 500 feet. At those
distances, even assuming that the antennas are oriented directly toward someone, the
levels are some 75 times and 1,900 times below the federal WE, respectively.
No. 4: Exposure must take into account the power density and the length of exposure.
Exposure increases in a non -linear manner with time. Hazards are greater for
adolescents, young children babies, seniors & pregnant women.
Response: Yes, exposure assessment must take into account the power density, while
the length of exposure only applies if the power density levels EXCEED the WE. That
is, exposures below the WE are allowed 24 hours a day, 7 days a week. Exposures to
radio frequency energy above the WE are allowed for short durations, provided that the
average over any 30-minute period is less than the WE. This is an important point
about radio frequency energy; it is NON -ionizing and so does not have a cumulative
effective over time.
No. 5: RF energy will affect children & parents passing by antennas on the way to
schools: Regnart Elementary, Kennedy Middle, & Monta Vista High.
Response: Since by the definition of the standard there is no effect on children,
parents, or anyone else at exposure levels below the standard, and since exposure levels
for a person anywhere at ground from the proposed operation will be at least 800 times
below the standard, then children and parents going to these schools will not be affected.
Mr. Jung, page 3
October 26, 2010
No. 6: It is not lawful to install a personal wireless service facility on a low -height
pole in a residential area.
Response: It is not against the FCC standard to install a personal wireless service
facility at any location, including a low -height pole in a residential area, provided that
facility does not cause RF exposure levels to exceed the federal MPE. The T-Mobile
proposal does not cause RF exposure levels to exceed the federal MPE
No 7: Based on our calculations taking into account the hilly terrain on the west and
south sides of the project, the expected exposure will be hazardous.
Response: I have not reviewed any calculations by others that were submitted in this
matter, but in light of the fact that the MPE cannot be exceeded beyond 12 feet from the
antennas, which are to be installed some 44 feet above ground, there is no location, to
the west, south, or anywhere else, where the expected exposure will exceed the MPE,
which is established by the FCC to be fully protective against hazard.
No. 8: The City should consider siting all wireless carrier facilities in the Cupertino
hills, to cover Bubb Road, Regnart Road & Lindy Lane.
Response: I have not reviewed the siting and coverage decisions that T-Mobile makes
internally. Our role is simply to assess the proposal for compliance with the FCC
standard.
We appreciate the opportunity to be of service and would welcome any questions on this
material. Please let me know if we may be of additional assistance.
Sincerely yours,
William F. Hammett
lc
Enclosure
cc: Ms. Dayna Aguirre (w/encl) - BY E-MAIL DAGUIRRE@SUTROCONSULTING.COM
Mir. Ryan Crowley (w/encl) - BY E-MAIL RCROWLEY@SUTROCONSULTING.COM
Mr. Mike Dipiero (wlencl) - BY E-MAIL MIKE.DIPIERO@T-MOBILE.COM
Mr. Tred Haglund (wlencl) -BY E-MAIL TRED.HAGLUND@CHARTER.NET