08O. Appendix OP.O. Boa 17 • Helena, Montana 59624
Tel: (406) 457-0407 • Fax: (406) 442-1296
www.bigskyacousaa.com
Big Sky Acoustics, uc
January 4, 2012
Mr. Jeff Walla
Stelling Engineers, Inc.
1372 Airport Road
Kalispell, MT 59901
Re: Kalispell City Airport
Airport Noise Contours
BSA Project #09139
Dear Jeff:
Big Sky Acoustics, LLC (BSA) has completed the noise contour analysis for the Kalispell city
Airport. The attached report provides the details and results of the noise study.
Thank you for your continued confidence in BSA. If you have any questions or comments
regarding the information presented in the report, please do not hesitate to call me at (406) 457-
0407, or email me at sean@bigskyacoustics.com.
Sincerely,
Sean Connolly, P.E. (OR)
BIG SKY ACOUSTICS, LLC
Attachment
P.O. Box 21 • Helena. Montana 59624
Tel: (406) 451-0401 • Fax: (406) 442-1296
www.hi gskyacousti cs.coiu
Big Sky Acoustics, uc
KALISPELL CITY AIRPORT
NOISE CONTOUR ANALYSIS
January 4, 2012
1.0 INTRODUCTION
The Kalispell City Airport (KCA) is a general aviation airport, and its Master Plan is being
updated to evaluate the airport's capabilities and to provide guidelines for the airport's overall
maintenance, development and operation (Stelling 2011 a). Three development alternatives were
recommended for further study in the Update:
• Alternative A: Constructing a new runway alignment.
• Alternative B: Improving the existing runway.
• Alternative C: Relocating the KCA to a new site northwest of Kalispell.
The City of Kalispell requested that noise contours be developed for the KCA alternatives to
determine the potential noise impact of predicted airport operations on adjacent properties.
Airport noise contours are used for land use planning purposes to ensure that noise -sensitive
development does not occur too close to an airport. The noise contour analysis was conducted by
Big Sky Acoustics, LLC (BSA), in accordance with Federal Aviation Administration (FAA)
Order 5050.4A, The Airport Environmental Handbook.
2.0 NOISE TERMINOLOGY
Noise levels are quantified using units of decibels (dB). Noise levels can also be expressed as A -
weighted decibels (dBA). Humans typically have reduced hearing sensitivity at low frequencies
compared with their response at high frequencies, and the A -weighting of noise levels closely
correlates to the frequency response of normal human hearing. By utilizing A -weighted noise
levels in a study, a person's response to noise can be assessed.
Decibels are logarithmic values, and cannot be combined using normal algebraic addition. For
example, the combined noise level of two 50-dBA noise sources would be 53 dBA, not 100
dBA, and the combination of a 50 dBA noise level and a 40 dBA noise level would still be 50
dBA.
The day -night average noise level, DNL, is a single number descriptor that represents the
constantly varying sound level during a continuous 24-hour period. The DNL includes a 10 dBA
penalty that is added to noises that occur during the nighttime hours between 10:00 p.m. and 7:00
a.m., to account for people's higher sensitivity to noise at night when the background noise level
is typically lower.
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Kalispell City Airport Master Plan Update Big Sky Acoustics, LLC
Noise Contour Analysis
Airport noise contours are normally presented in terms of DNL values in units of A -weighted
decibels, in increments of 5 dBA. The contours are based on the annual number of flight
operations at an airport and the airport fleet mix. The FAA considers the DNL metric useful for
airport noise studies because it uses a single number to describe the constantly fluctuating noise
levels at a receiver location during an average 24-hour day. The use of DNL contours is meant to
provide a general indication of impact and is not intended to determine the reaction of people due
to individual events, such as a single take -off or landing.
3.0 FAA REQUIREMENTS
The Aviation Safety and Noise Abatement Act of 1979 required the FAA to establish a single
system for determining noise exposure at properties in the vicinity of airports, and the FAA was
required to set up a standardized airport noise and land compatibility planning program. With the
adoption of FAR Part 150, Airport Noise Compatibility Planning, the FAA established that noise
contour maps would be used as a planning tool to determine if land located near airports is
compatible with the operation of the airport, and to determine if noise -sensitive locations near
airports would be negatively impacted by changes to an airport or its operations. This document
determined that residences and schools should not be located within the DNL 65 dBA contour
associated with an airport.
The FAA's Airport Environmental Handbook does not require a noise exposure contour analysis
for the KCA since its projected 24,754 annual flight operations in the Design Year 2030 (Stelling
2011a) do not exceed 90,000 annual propeller operations. However, the City determined that an
analysis of the KCA noise contours would be beneficial for the Project.
Please note that the predicted DNL contours for any airport do not precisely define impacts. The
purpose of the noise contours, and specifically the DNL 65 contour, is to highlight potential
incompatibilities between an airport and surrounding development, assess relative noise
exposure levels, and provide guidance for the development of land -use control devices, such as
zoning ordinances, subdivision regulations and building codes.
4.0 ANALYSIS
The intent of this noise analysis was to determine the noise contours for each of the development
alternatives. Each alternative includes the construction of a 3,600 foot runway, and the land
acquisition necessary for potential future improvements and runway extensions. For the analysis,
the number of flight operations and the fleet mix were evaluated, and used to calculate the
contours. The location of the DNL contours were then overlayed on to figures from the Master
Plan Update to compare the locations of the contours to the location of the airport property lines
and land uses in the vicinity of the airport.
4.1 The Integrated Noise Model (INM)
The FAA developed the Integrated Noise Model (INM) software to predict noise contours for
airports. BSA used INM Version 7.0 for the KCA analysis. INM is designed to estimate the
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Kalispell City Airport Master Plan Update Big Sky Acoustics, LLC
Noise Contour Analysis
average annual noise levels due to the operations at an airport. Therefore, differences between
predicted and actual noise levels may vary on any given day because certain specific
occurrences, such as number of flight operations, specific aircraft type, etc., may not be
explicitly modeled in INM.
To compute noise contours, INM uses the number of average annual flight operations, the type
of aircraft using the airport, and the time of day that flight operations occur. The elevation of
runway endpoints, the overall length of a runway, and the width of the runway to define the
beginning and endpoint of flight operations on the runway were also entered into the model. The
flight operations at an airport include approach, departure and touch-and-go operations that occur
during an average day associated with a certain type of aircraft.
Since the calculation of the DNL metric is based on the time of day when a noise -producing
event occurs, flight operations are separated into those that occur during the daytime hours (7:00
a.m. to 10:00 p.m.) and nighttime hours (10:00 p.m. to 7:00 a.m.) for a 24-hour period.
4.2 Flight Operation Data
The noise contours developed by BSA are based on the fleet mix and forecast flight operations
stated in the the Master Plan Update (Stelling 2011 a). Based on additional information, 5% of
operations occur at night, and the preferred runway at the existing KCA is Runway 13 (Stelling
2011b). Aircraft using Runway 13 take off to the southeast and arrive from the northwest. BSA
assumed that 60% of all flight operations would use the Runway 13 orientation for Alternative B,
and that 50% of those operations were departures and 50% were arrivals. Since the runway
orientation of each alternative is similar, BSA assumed that Runway 12 would be the preferred
orientation for Alternative A, and Runway 14 would be preferred for Alternative C.
In the Master Plan Update, Table 4-9 included the estimated number of operations for each type
of aircraft in the fleet mix for the current year 2011. Using the data in the table, BSA calculated
the percentage of the total operations for each aircraft type. Since the length of the runway for
each alternative is the same as the existing KCA runway (3,600 feet), BSA assumed the
percentages would be similar in the Design Year 2030 for each alternative.
Table 4-1 indicates the forecasted data that was input into the INM model to calculate the noise
contours. The alternatives do not include extending the runway at this time, and operation data
for aircraft that could utilize a longer runway, such as jets, were not provided (Stelling 2011 a).
The Design Year of the project is 2030.
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Kalispell City Airport Master Plan Update
Noise Contour Analysis
Table 4-1: Estimated KCA Fleet Mix and Operations
Big Sky Acoustic, LLC
"ClPercentage
Percentage of
Percentage of
Design
of Total
Daytime
Nighttime
GroUV2
Tvpes of AircraftZ
Operations
Operations
Operations
A -I
Single engine aircraft, such as
85%
95%
5%
Cessna 172.
B-I
Twin engine aircraft, such as
0.4%
95%
5%
Cessna 340
B-II
Twin engine turboprop aircraft,
0.4/o 0
95%
5%
such as Beechcraft Kine Air C90.
Rotorcraft
Helicopter, such as the Bell 206
14.2%
95%
5%
series.
Notes
1. Airport Reference Code.
2. Stelling 2011a.
5.0 RESULTS
The predicted noise contours for each of the development alternatives are shown on Figures 1
through 4. As shown for each alternative, the DNL 65 contour will be located within the
proposed airport boundary for Alternatives A and C in the Design Year 2030, and within the
existing airport boundary for Alternative B in the Present Year 2011 and Design Year 2030.
Therefore, the DNL 65 contour is not predicted to extend onto adjacent properties, and negative
noise impacts should not occur on properties in the vicinity of the airport according to the FAA
criteria.
Although the FAA criteria is predicted to be met in the area surrounding Alternative C, noise
annoyance in a community may be much greater than predicted when a new, unfamiliar noise
source is introduced to an area. DNL adjustments or +10 to +15 dBA may be necessary to assess
the true impact of the proposed Alternative C location (ISO 2003). Therefore, the predicted DNL
50 dBA contour shown on Figure 4 would be adjusted to DNL 60 to 65 dBA. Although several
houses are shown just outside the DNL 50 (adjusted DNL 60-65) contour, the aircraft operations
may still generate a negative community reaction.
6.0 STANDARD OF CARE
To complete this report, BSA has endeavored to perform its work in a manner consistent with
that degree of care and skill ordinarily exercised by members of the same acoustical profession
currently practicing under similar circumstances. BSA makes no warranty, either express or
implied, as to the professional services it has rendered to complete this report.
For the completion of this report, BSA has used data provided by Stelling Engineers in
performing services and is entitled to rely upon the accuracy and completeness thereof.
Therefore, if the information (i.e., flight operation data, proposed runway configurations, aircraft
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Kalispell City Airport Master Plan Update
Noise Contour Analysis
Big Sky Acoustics, LLC
type, etc.) and assumptions used to create this report change, then the predicted noise contours
may need to be reevaluated.
7.0 REFERENCES
International Organization for Standardization (ISO). 2003. Acoustics — Description,
measurement and assessment of environmental sound — Part 1: Basic quantities and assessment
procedures. Standard Designation: 1996-1.
Stelling Engineers (Stelling). 2011a. Kalispell City Airport Master Plan Update — Draft. Dated
December 12, 2011. Viewed at City of Kalispell website
htt://www,kalis ell.com/ma or and cily council/Ci A' ortInforrnation. h . December 27.
Stelling Engineers (Stelling). 2011b. Email from Mike Beckhoff indicating percentage of night
usage and preferred runway usage. November 23.
Page 5 of 5
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