2003
Mather Field jet freighter approach noise:
Conclusions
and comments
evaluation and
opinion by Paul Raveling
In brief:
Does El Dorado Hills have a noise
problem with jet freighter approaches?
No, not as a community. Overall (CNEL) measurements show that El Dorado
Hills is still exceptionally quiet, generally much like a tomato field
on a farm.. Single event (SENEL) measurements showed generally
reasonable maximum noise levels. However, in extreme cases, a very
small portion of approaches, single event noise can be loud enough to
be objectionable to some residents living beneath the approach path.
Whether or not this level of noise is a problem depends on individual
sensitivities.
Does El Dorado Hills have a
problem with complaints about noise?
Yes. A small number of complainants have stridently asserted that
approach noise is extremely excessive. Many of their claims concerning
noise levels and altitude of freighters on approach have not been
substantiated by measured data. A few other residents have complained
about noise in a more reasonable way.
Conclusions (my personal opinions
only)
Freighter noise on approach does not rise to a level that compels
public action. It can be a problem for individuals, and the appropriate
response is individual action: If noise is a problem at a given
location, choose to live in a different location. The noise footprint
of jet aircraft is extremely narrow, locations quiet enough to be
suitable for any reasonable person can be only a few blocks to the
north or south of a questionable location.
The VOR/DME approach test in 2003 demonstrated that the ILS approach is
quieter. There is reasonable latitude for future regulation to reduce
noise further by implementing a stepped approach on the ILS, with an
initial outer segment mildly steeper than the standard 3-degree glide
slope.
Do we have a noise problem?
 |
with
apologies to Edvard Munch
for a crude cartoon
inspired by The Scream
|
We definitely do NOT have a CNEL noise
problem. The tests showed that El
Dorado Hills has no more overall noise than a tomato field on a farm,
perhaps even less. Our CNEL measurements are a minimum of 10 dB quieter
than the most restrictive CNEL noise levels in various localities in
the U.S.; they are 20 dB quieter than the most permissive standards for
maximum noise to delimit an airport influence area.
Single event noise is generally quite
reasonable, but there are occasional approaches that reach marginal
noise levels. The usual complaints
are about sleep-disturbing early morning arrivals, around 4 a.m.
The VOR/DME test showed that the ILS approach provides significantly
reduced exposer to individual oud approaches than the VOR/DME
(nonprecision) approach. Aircraft on the VOR/DME approach generally
descend earlier and some cross the El Dorado Hills/Folsom area as low
as 2,000 feet MSL. The ILS crossing altitude on the ridge at El Dorado
Hills is about 3,800 feet MSL.
Noise is a major factor in identifying an Airport Influence Area (AIA). Each
AIA is mapped to suit a particular airport, and most are defined by
noise contours and terrain clearance requirements for safe flight. In
many cases local regulations restrict zoning within an AIA to land uses
compatible with given noise levels. This is usually based on a 65 dB
noise contour, but some AIAs also use a 60 dB noise contour. A much
smaller number use a 55 dB contour. AIAs usually extend up to 2 miles
from ends of the runways. In contrast, El Dorado Hills locations are at
least 12 miles from Mather Field, at least 5 times the distance
normally included in an AIA.
It appears that noise is not a major public issue, provided that
freighters follow the ILS approach path and the aircraft remain on or
above the glide slope. It is still likely that low
approaches occasionally will be loud enough to disturb individual
residents; this depends on both individual sensitivity and the noise
itself. The area subject to this level of exceptional noise is a very
narrow band under the approach path.
Do
we have a complaint problem?
Yes.
The stridency of complaints from a small group of residents is
disproportionate to what the 2003 noise test measurements showed and to
the subjective impressions of others who also live below the standard
ILS approach path.
To a substantial degree this is more about human nature than physical
reality. Consider these citations from other circumstances,
beginning with a slightly updated chart published originally in a 1971
EPA document , relating public response to CNEL noise levels:
Actual noise measurements do not appear to warrant the level of
complaints recorded from El Dorado Hills and Folsom. According to the
EPA chart abovewe should expect no complaints about jet
freighters and very few if any complaints about noise from other
sources.
Aircraft noise has a history of disproportionate and even irrational
responses. Here are two
examples:
- In the year that ended in March, 2001, San Francisco
International Airport (SFO) logged about 52,000
noise complaints from 2,819 people. 21,860 of these complaints came
from just one woman who lived in a part of Foster
City outside of the area at highest risk of noise exposure. In
contrast, SFO statistics in December, 2003 showed 5 noise
complaints from 3 people in Foster city during the preceding month.
- Noise tests were conducted in 1999 at El Toro, the former Marine
Corps air base. Advance notice to the public indicated exactly when a
747 would arrive and land to start the tests. At that appointed time
numerous residents called in noise complaints. The catch was that
the airport was fogged in, the 747 was orbiting off the coast and
didn't land until much later in the day. There was absolutely no jet
noise at the time.
The Foster City example illustrates
another difference that can only be
attributed to personal sensitivities. This is the approach in
question,
The runway 28L approach just crosses the edge of Foster City, as shown
by the flight track nearest the bottom in this snapshot. Consider a comparison of the Foster City
location where the 28L approach crosses highway 92 and El Dorado Hills
site 3, where the ILS approach to Mather runway 22L crosses the local
ridge:
Location
|
Distance from runway threshold, statute miles
|
Typical crossing altitude, agl
|
CNEL
noise level |
Number of approaches per day
|
Number of
local noise complaints
per month
|
Complaints per caller
|
Foster City
|
5.9 miles
|
1,900 ft
|
less than 65 dB
|
119
|
5
|
1.7
|
El Dorado Hills
|
12.85 miles
|
2,800 ft
(3,800 MSL)
|
less than 45 dB
|
6
|
244
|
6.8
|
SFO complaint numbers are for
one month
in 2003. Complaint data on a per month basis is for Mather is derived
data for four months in the 2003 SCAS study by dividing the 4-month
complaint count by 4. At both sites actual crossing altitudes tend to
cluster within about 100 feet of the indicated altitude.
The number of approaches for SFO was reported for one day in
January, 2004 in a phone contact with the SFO noise abatement office. .
On this day runways 28L and 28R handled a total of about
480 approaches; controllers use runway 28R as much as possible to
minimize noise exposure in Foster City. The number of approaches per
day for Mather is the median approach count reported in the 2003 SCAS
study.
A recent report on SFO noise is available at this link.
Data tabulated above shows a very clear difference between El Dorado
Hills and Foster City for both real physical circumstances and the
consequent level of complaints. A reasonable inference is that
either EDH complaints are unrealistic (more than warranted), Foster
City complaints are unrealistic (less than warranted), or both sets of
complaints are unrealistic. The SFO numbers appear reasonably
consistent around the Bay Area: Most noise complaints come from
areas such as Daly City and South San Francisco, within the 65 dB CNEL
noise contour on the departure path from SFO.
Numerous public meetings in the Sacramento area provide evidence for
the first possibility; for example, the most vocal anti-noise activists
often claim that the airport system intends to grow to support several
hundred freighter approaches per day at Mather. Data in the Mather
Airport Master plan provides a more realistic projection of growth,
with the current 6 approaches per day roughly doubling by 2020. Other
statements by local anti-noise activists show clear evidence that they
do not understand the air traffic system issues and so far have been
either unwilling or unable to learn.
The El Dorado Hills applicants have at
best limited credibility. I regret to conclude that their
complaints should be discounted in deciding public policy.
Information on this page is based
on these public documents, from the Sacramento County Airport System:
Most of the graphics in this set of web pages are extracted from these
documents, with permission from and thanks to SCAS. In many cases
portions of them have been highlighted to emphasize portions relating
directly to El Dorado Hills.
