HomeMy WebLinkAbout3583; Cannon Road Lift Station; Cannon Road Lift Station Operational Noise; 2005-11-01CITY OF CARLSBAD
DEPARTMENT OF PUBLIC WORKS
CANNON ROAD LIFT STATION
OPERATIONAL NOISE SURVEY REPORT
NOVEMBER 2005
Prepared for:
CITY OF CARLSBAD
Public Works Department
1635 Faraday Avenue
Carlsbad, CA 92008
Prepared by:
DHK ENGINEERS, INC.
1851 SKYHILL PLACE
ESCONDIDO, CALIFORNIA 92026
(760) 747-9553
3S*?
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
TABLE OF CONTENTS
1.0 INTRODUCTION 1
2.0 NOISE CRITERION AND ASSUMPTIONS 2
2.1 NOISE BACKGROUND 2
2.2 NOISE CRITERION 2
3.0 FIELD METHODOLOGY AND INSTRUMENTATION 3
4.0 AMBIENT NOISE SURVEY RESULTS 4
5.0 CONCLUSIONS AND RECOMMENDATIONS 4
LIST OF TABLES
Table 2-1: Typical Noise Source Levels in dB(A) 2
Table 2-2: Residential Exterior Acoustical Design Criterion 3
Table 4-1: Ambient Noise Measurements at the CRLS Fenceline, 1130 pm to 1230 am, October 19-20,
2005 4
LIST OF FIGURES
Figure 1: Site Map 5
APPENDIX
APPENDIX A Acoustical Terminology
APPENDIX B Noise Monitoring Location Photographs
APPENDIX C Sound Meter Certifications
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
1.0 INTRODUCTION
The City of Carlsbad (City) recently completed the design and construction of the Cannon Road Lift
Station (CRLS). The lift station has a 2.8-million gallon per day (mgd) average flow capacity and 6.6 mgd
PWWF at ultimate build-out. The location is adjacent to the existing lift station east of the new extension
of Cannon Road, and occupies part of the existing storm water desilting basin (See Figure 1 at rear of
text).
Based on the previous Noise Impact Study (STUDY) completed by DHK Engineers, Inc. (DHK) in
support of the design effort, this confirmation noise survey was conducted to confirm the noise mitigation
measures as defined within the STUDY. The operations noise survey was conducted during late night
hours on October 19, 2005. The late night hours were selected to ensure that the ambient background
noise was sufficiently low to demonstrate no net increase in dB(A) from CRLS to the surrounding area.
Since the lift station operates continuously (24 hours per day and 7 days per week), the noise signature is
consistent throughout the day and night time periods and would be most representative during the selected
late night period.
OBJECTIVE AND METHODOLOGY
The objectives of this analysis are to:
1. Verify that the City of Carlsbad Design Criteria for the noise control aspects of the project are
in compliance with the City's General Plan noise criterion.
2. Measure the ambient noise surrounding the station during late night hours for comparison
purposes.
3. Determine if additional noise reduction measures are warranted to comply with the City's
noise criterion at the nearest receptors.
The methodology used in the analysis is as follows:
1. Establish ambient noise levels during worst case conditions (late night) regulatory noise
impact goals at critical receptors in the area surrounding CRLS, including the adjacent
residential community.
2. Evaluate the existing noise in the project area and compare the incremental increase to the
nighttime minimum decibel requirement of 45 dB(A)
3. Determine if any noise impacts associated with mechanical equipment at CRLS exist, and
provide recommendations for mitigation, if warranted.
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
2.0 NOISE CRITERION AND ASSUMPTIONS
The noise nuisance criterion is presented in this section. In addition, a description of the noise simulation
model and the assumptions applied to determine noise levels at critical receptors are presented.
2.1 NOISE BACKGROUND
Sound is mechanical energy transmitted by pressure waves in a compressible medium such as air. Noise
is unwanted sound. Sound is characterized by various parameters that describe the rate of oscillation of
sound waves, the distance between successive troughs or crests, the speed of propagation, and the
pressure level or energy content of a given sound. In particular, the sound pressure level has become the
most common descriptor used to characterize the loudness of an ambient sound level.
The decibel (dB) scale is used to quantify sound intensity. Because sound pressure levels can vary by over
one million times within the range of human hearing, a logarithmic loudness scale (similar to the Richter
Scale used for earthquake intensity) is used to keep sound intensity numbers at a convenient and
manageable level. Since the human ear is not equally sensitive to all sound frequencies within the entire
spectrum, noise measurements are weighted more heavily within those frequencies of maximum human
sensitivity (middle A and its higher harmonics) in a process called "A-weighting," written as dB(A).
Table 2-1 illustrates the typical A-weighted sound level of representative noise sources. Acoustical
terminology definitions are provided in Appendix A.
Table 2-1: Typical Noise Source Levels in dB(A)
Noise Source
Noise at ear level from rustling leaves
Room in a quiet dwelling at midnight
Soft whisper at five feet
Large Department Store
Room with window air conditioner
Conversational Speech
Passenger Car at 50 ft.
Vacuum cleaner in private home at 10 feet
Ringing alarm at two feet
Reference: Noise Control Reference Handbook, Industrial Acoustics Company
2.2 NOISE CRITERION
dB(A)
20
32
34
50 to 65
55
60 to 75
69
69
80
Bulldozer at 50 ft
Heavy city traffic
Home lawn mower
Jet aircraft at 500 feet overhead
Human pain threshold
87
90
98
115
120
Residential design criterion throughout the State of California range from a daytime ambient level of 55
dB(A) to an evening level of 45 dB(A). Industrial noise level impacts are based on the property line noise
limits for stationary noise generators in a residential area as summarized in Table 2-2 below:
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
Table 2-2: Residential Exterior Acoustical Design Criterion
Time Period Applicable Limit 1-Hour Average Sound Level
in Decibels-dB(A)
0700 -1900 (7 am to 7 pm) 55
1900 - 0700 (7 pm to 7 am) 45
Reference: City of Carlsbad General Plan - Noise Guidance
3.0 FIELD METHODOLOGY AND INSTRUMENTATION
An ambient noise survey was conducted in the project area on October 19-20, 2005 to document existing
operational noise levels within CRLS. Five monitoring locations were selected in close proximity to
CRLS to measure fenceline noise levels. Each noise location was monitored during late night hours to
minimize ambient noise from sources not associated with CRLS operations. The monitoring events were
completed between 2300 and 0030 starting in the late evening on October 19, 2005 and ending during
early morning hours on October 20. Figure 1 illustrates the noise monitoring locations relative to the
CRLS.
Continuous A-weighted sound measurements were made over a 10-minute period using a CEL Model
480 sound level meter. The instrument was equipped with optional circuitry and microphones that meet
the requirements of ANSI S1.4 for Type II precision sound level meters. The Bruel & Kjaer (B&K) Type
4936 pre-polarized random incidence microphone is an integral part of the sound meter. The sound meter
was positioned at a height of about 5 feet above the ground at locations indicated on Figure 1. Foam
windscreens of 3.5-inch diameter were used to minimize wind-generated noise.
The calibration levels of the instrument were checked before and after each monitoring period using a
CEL-282 sound level calibrator. All intermittent calibrations were verified and were within the normal
error band. Instrument certifications are provided in Appendix C.
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
4.0 AMBIENT NOISE SURVEY RESULTS
The noise survey confirmed current operational conditions based on the ambient noise characteristics
associated with residential areas. The results of the survey (in L^n and !,«,) are presented in Table 4-1 for
the five monitoring locations indicated on Figure 1.
Table 4-1: Ambient Noise Measurements at the CRLS Fencetine, 1130 pm to 1230 am, October 19-20,2005
Noise
Monitoring
Location (NMLj*
1"
2
3
4
" T~ •
Location Description
j Nearest Residential
I Receptor (east of CRLS)
j Southeast of chemical
( loading area
I South Gate near easement
| Northwest Comer of CRLS
\ Northeast CRLS Gate
Minimum
Noise Level
L,mn in dB(A)
40.5
56.1
45.5
56.3
41.6
Equivalent
Noise Level
Leq in dB(A)
48.1
69.1
54.4
58.1
51.8
Potential Noise Problem
Observations
Access hatch to wet well
Noticeable rattle adjacent to
south roll-up garage door
Notes:
(*) Photographs of each noise monitoring location are provided in Appendix B
(") Critical Receptor Location (used to compare with the City of Carlsbad General Plan Noise Criterion)
During the noise survey it was apparent that although Noise Monitoring Location (NML) #1, a critical
residential receptor, complied with the noise criterion of less than 45 dB(A) during nighttime hours, the
access hatch to the wet well exhibited partial leakage of noise from around the hatch gaskets area. Also,
adjacent to the south roll-up garage door, a noticeable rattle was identified and should be considered a
continuous nuisance.
5.0 CONCLUSIONS AND RECOMMENDATIONS
The following conclusions and recommendations were derived from noise data obtained during field
measurements as presented in Table 4-1 above:
1. Noise reduction objectives were fully achieved at the critical residential receptors (NML #1).
2. Although noise reduction objectives were achieved as of November 2005, installation of a rubber
mat over the wet well hatch and investigation into the source of the rattle noise on the south west
comer of the CRLS is recommended.
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
APPENDIX A
ACOUSTICAL TERMINOLOGY
A-l
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
Acoustical Terminology:
Ambient Noise: The sound pressure levels associated with a given environment. Ambient noise is a
composite of sounds from near and far sources none of which are particularly dominant.
Background Noise: The sound pressure levels in a given environment from all sources excluding a
specific sound source being investigated or measured.
Barrier: Any obstacle placed between the source and the receiver to reduce the noise impact on the
receiver.
CNEL: Community Noise Equivalent Level is an idex or metric of community noise. The metric used in
California for quantifying aircraft and community noise levels, usually within 1 dB (higher) than Ldn for
most community noise sources. CNEL adds 5 dB between the hours of 7:00 p.m.-10:00 p,m, and JOdB
between the hours of 10:00 p.m.- 7:00 a.m., which is slightly different than L<jn.
Day-Night Average Sound Level (La,,): The A-weighed equivalent continuous sound exposure level for
a 24-hour period with a 10 dB adjustment added to sound levels occurring during nighttime hours of (10
p.m. to 7 a.m.)
Decibel "A" Scale: Sound level weighting which approximately represents the frequency response of the
human ear, which is less sensitive to low frequency than to high frequency sound.
Far Field Noise: Noise acting in accordance to the inverse law. Double the distance- reduce the dB(A) by
"6".
Leq: Equivalent sound level. The dB(A) level of a steady state sound which has the same dB(A)
weighted sound energy as that contained in the actual time-varying sound being measured over a specific
time period.
Noise Control: Usually involves three elements including 1) A noise source, 2) a receiver of noise and 3)
various paths noise can travel between the source and receiver.
Sound Absorption Coefficient: The dimensionless ratio of the sound energy absorbed by a given surface
to that incident upon the surface.
Sound Receiver: One or more observations points at which sound is evaluated or measured. The effect
of sound on an individual receiver is usually evaluated near the ear or close to the body.
Speed of Sound in Air: 1,129 feet per second
A-2
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
APPENDIX B
NOISE MONITORING LOCATION PHOTOGRAPHS
B-l
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
NOISE MONITORING LOCATIONS
Noise Monitoring Location #1 - Critical Residential Receptor
Noise Monitoring Location #2- CRLS with wet well hatch in foreground
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
Noise Monitoring Location #3- South side of CRLS
Noise Monitoring Location #4- Adjacent to CRLS South comer
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
Noise Monitoring Location #5- Main Driveway (north side)
CANNON ROAD LIFT STATION OPERATIONAL NOISE SURVEY REPORT NOVEMBER 2005
APPENDIX C
SOUND METER CERTIFICATIONS
c-i
Ashtead Technology Rentals
Certificate of Compliance and Calibration
Model No.: CEL-480 Customer: Ashtead Technology Rentals
Serial No: 100278 ID No: R4366 Purchase Order: Internal
Date of Calibration: 2/3/05 Date Due: 2/3/06
Accuracy: ANSI Type 2 Temperature: 70.5 F Relative Humidity: 47.1%
Condition of Instrument Received
Condition Received: In Tolerance
Remarks:
Condition of Instrument Returned
Condition Returned: In Tolerance
Remarks: Device meets ANSI Type 2 specifications under laboratory
conditions for logging dosimeters/sound level meters.
Standards Used
Standards: Due Date:
Quest QC-20 Sound Calibrator ANSI S 1 .40 S/N QF408000 1 03/27/04
Quest 1700 Imp Sound Level Meter ANSI S1.40 S/N OHT01 1001 1 03/27/04
Quest -Cal Acoustic Calibrator S/N KZ7060007 03/27/04
Bruel & Kjaer 4936 Microphone S/N 2129138 03/27/04
Edgetech 2002 Dew Point Hygrometer S/N 027579/1D1 137M 03/13/04
Ashtead Technology does hereby certify that the above listed Sound Level Meter/Noise
Dosimeter meets or exceeds the manufacturer's specifications and has been calibrated using
standards and instruments whose accuracies are traceable to the National Institute of
Standards and Technology (NIST). This report cannot be reproduced without prior
approval from Ashtead Technology.
Date: 2/3/05
Ashtead Technology, 18195 McDurmott East, Suite A/B, Irvine, CA 92461
Tel:949-955-3930 Fax: 949-955-3932
Ashtead Technology Rentals
Certificate of Compliance and Calibration
Model No.: CEL-282 Customer: Ashtead Technology Rentals
Serial No:3/03123989 IDNo:N/A Purchase Order: Internal
Date of Calibration: 2/3/05 Date Due: 2/3/06
Accuracy: +/-O.ldb Temperature: 70.5 F Relative Humidity: 50.9%
Condition of Instrument Received
Condition Received: In Tolerance
Remarks:
Condition of Instrument Returned
Condition Returned: In Tolerance
Remarks: Device meets ANSI standard Sl.40-1984 and IEC 942-1988 for sound
calibrators under laboratory conditions.
Standards Used
Standards: Due Date:
Quest QC-20 Sound Calibrator ANSI SI.40 S/N QF4080001 04/13/05
Quest 1700 Imp Sound Level Meter ANSI S1.40 S/N OHT0110011 04/13/05
Quest -Cal Acoustic Calibrator S/N KZ7060007 04/13/05
Bruel & Kjaer 4936 Microphone S/N 2129138 04/13/05
stech 2002 Dew Point Hygrometer S/N 027579/1D1137M 03/20/05
Ashtead Technology does hereby certify that the above listed Sound Level Meter/Noise
Dosimeter meets or exceeds the manufacturer's specifications and has been calibrated using
standards and instruments whose accuracies are traceable to the National Institute of
Standards and Technology (NIST). This report cannot be reproduced without prior
approval from Ashtead Technology.
Approved by: VICTOR VEGA Date: 2/3/05
Ashtead Technology, 18195McDurmott East, Suite A/B, Irvine, CA 92461
Tel: 949-955-3930 Fax: 949-955-3932