HomeMy WebLinkAbout3184; CANNON ROAD WEST; MITIGATION MONITORING RESULTS, WEEKS 20 & 21; 1999-08-27RECEIVE
&gative Science and Engineering AUG 3 '0 1999
3511 Camino Del Rio South, Suite 302
San Diego, CA 92108-4003
Phone/Fax: 619-640-9379 /619-640-0763
www.ise-advJtJ&'daERlNG
DEPARTMENT
August 27, 1999
Mr. Doug Gettinger
Ogden Environmental and Energy, Inc.
5510 Morehouse Drive
San Diego, CA 92121
Re: Cannon Road Mitigation Monitoring Results - Week #21 (8-26-99)
(ISE Report #99-009u, 035)
Dear Mr. Gettinger:
Pursuant to U.S.F.W.S. permit approval requirements, Investigative Science
and Engineering (ISE) has examined potential noise impacts to the riparian habitat
along the proposed Cannon Road extension alignment located in Carlsbad, California.
A field survey of the site was performed on August 26, 1999. The results of that survey
are presented in this letter report.
ISO Introduction and Definitions
Site Characterization
The Cannon Road West Project is located in the City of Carlsbad in San Diego
County, California (refer to Figure 1). This project will extend Cannon Road
approximately 2 miles east from its terminus at I-S to El Camino Real. The Cannon
Road extension consists of two bridge crossings and traverses through and adjacent to
habitat for the federally endangered/threatened least Bell's vireo, southwestern willow
flycatcher, and California gnatcatcher.
The predominate' land use of the project area is undisturbed open space.
Wetlands originating from the Agua Hedionda Lagoon and Agua Hedionda Creek are
located adjacent to the north and commercial developments are present to the west.
Elevations for the project area have been altered due to construction activities;
however, pre-construction elevations range from approximately 100 feet above mean
sea level (MSL) along the terrace over looking Agua Hedionda Lagoon down to
approximately 5 feet above MSL along the banks of the Agua Hedionda Creek.
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results -Week #21 (8-26-99)
ISE Report #99-009u, 035
August 27, 1999
Page 2
.: . .
1
-
/
1127 / ,jL_
C:
ProjectPJignmen
1' Area \ . • : '1 ___________
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.. 'C
,-•' ______
ZV
Figure 1: Project Alignment Area Map (Thomas Guide Pages 1126, 1127, and 1107)
Acoustical Definitions
Airborne sound is a rapid fluctuation of air pressure above and below
atmospheric levels. The loudest sounds the human ear can hear conformably is
approximately one trillion (a one with 12 zeros following it) times the acoustic energy
that the ear can barely detect. Because of this vast range, any attempt to represent the
acoustic intensity of a particular sound on a linear scale becomes unwieldy. Because of
this, a logarithmic ratio known as the decibel (dB) is commonly employed. A sound level
of zero '0" dB is scaled such that it is defined as the threshold of human hearing and
would be barely audible to a human of normal hearing under extremely quiet listening
conditions and would correspond to a sound pressure level equal to the reference level.
Most of the sounds we hear in the environment do not consist of a single
frequency, but rather a broad band of frequencies differing in sound level. The
intensities of each frequency add to generate the sound we hear. The method
commonly used to quantify environmental sounds consists of determining all of the
frequencies of a sound according .to a weighting system that reflects the nonlinear
response characteristics of the human ear. This is called "A" weighting, and the decibel
level measured is called the A-weighted sound level (or dBA). In practice, the level of a
noise source is conveniently measured using a sound level meter that includes a filter
corresponding to the dBA curve.
Although the A-weighted sound level may adequately indicate the level of
environmental noise at any instant in time, community noise levels vary continuously.
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #21 (8-26-99)
ISE Report #99-009u, 035
August 27, 1999
Page
Environmental noise includes a conglomeration of sounds from distant sources that
create a relatively steady background noise in which no particular source is identifiable.
For this type of noise, a single descriptor called the Leq (or equivalent sound level) is
used. Leq is the energy-mean A-weighted sound level during a measured time interval.
It is the 'equivalent' constant sound level that would have to be produced by a given
source to equal the fluctuating level measured.
To describe time-varying character of environmental noise, the statistical noise
descriptors L10, L50, and L90 are commonly used. They are the noise levels equaled
or exceeded during 10 percent, 50 percent, and 90 percent of a stated time. Sound
levels associated with the L10 typically describe transient or short-term events, while
levels associated with the L90 describe the steady state (or most prevalent) noise
conditions. In addition, it is often desirable to know the acoustic range of the noise
source being measured. This is accomplished through the maximum and minimum
measured sound level (Lmax and Lmin) indicators. The Lmin value obtained for a
particular monitoring location is often called the acoustic floor for that location.
jB Applicable Significance Criteria
Wildlife Habitat Regulations
Construction and operational noise generated by this project is regulated by the
United States Fish and Wildlife Service (U.S.F.W.S.) and the California Department of
Fish and Game for its effect on federally endangered least Bell's vireo (Vireo be/Ill
push/us) and the southwestern willow flycatcher (Empidonax trail/fl extrimus) and the
federally threatened California gnatcatcher (Polio ptlla california).
Resource agencies have theorized that elevated noise levels can potentially
mask songs of the least Bell's vireo which are used to attract mates and defend
territories. The San Diego Association of Governments (SANDAG) in a 1990 study
entitled "Comprehensive Species Management Plan for the least Bell's vireo"
theoretically estimated that {traffic} noise levels above 60 dBA Leq in vireo breeding
areas may sufficiently mask the vireo's song and potentially reduce the reproductive
success of this species during their breeding season that occurs from March 1 to
September 1. Since sustained noise exposure (indicated by the L90 metric) produces
greater masking effects than intermittent peak levels, this report will analyze both
effects. The SANDAG report conclusions were unclear as to the specific time interval of
the measurement, but it is typically taken as one hour. Although research is on going
regarding similar noise impacts to the southwestern willow flycatcher and California
gnatcatcher, in the absence of species-specific data, these same study results .are
applied by the Service to this bird species as well.
4
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results -Week #21 (8-2699)
ISE Report #99-009u, 035
August 27, 1999
Page 4
Analysis Methodology
Existing Conditions Field Survey
Four Larson Davis Model 700 ANSI Type 2 integrating sound level meters were
used as the data collection devices. The meters were positioned at the locations shown
below in Figure 2 and the accompanying matrix.
:\!cp
ML #2
IVIL *1
)
,,/
'T;
/
-' - I ••.• - ¼
c,L4I 7
::
N T ;MN 0 1/2 1MILE ri I
/ I 1000 0 1000 2000 3000 4000 FEET
Figure 2: Project Area Topography (USGS 7.5 San Luis Rey Quadrangle 1:12000)
Monitor Sta. Eng. Sta. No. GPS Lat .GPS. Lon. Description
ML #1 102+00 330 08.780 N 1170 18.195W Western end of alignment
ML #2 113+00 330 08.826 N 1170 18.011 W Central point of alignment
ML #3 n/a 330 08.952 N 1170 17.895W Eastern end of alignment
ML #4 n/a 330 08.194 N 1170 18.401 W Macario Canyon Area
EPE = Estimated Position Error = 49'
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results.— Week #21 (8-26-99)
ISE Report #99-009u, 035
August 27, 1999
Page 5
The meters were mounted on tripods roughly 5 feet above the ground and were
calibrated before and after each field deployment. Each station was programmed to
record and log the following noise metrics each hour: Leq-h, Lmax, Lmin, L10, L50, and
L90.
Findings
Field Monitorina Results
A field survey was performed to ascertain construction noise levels within the
habitat area due to excavating, bridge fabrication, light grading and associated ancillary
activities. To date, the least Bell's vireo has been predominantly located between
station markers 103+00 and 108+00. These station markers correlate with ISE
monitoring locations 1 and 2. Additional sightings of the least Bell's vireo have been
observed within Macano Canyon (approximately 1-mile southwest of ISE monitoring
location ML 1) and in the /4 acre habitat located between the El Camino Real / Cannon
Road access bridge and the haul road entrance (approximately 300 feet south of ISE
monitoring location ML 3).
During the Week #21 monitoring period, no construction activities associated
with the Cannon Road West Project were identified. Activities and equipment observed
at Macario Canyon were associated with the proposed alignment of Faraday Road (to
connect with Cannon Road) and included five (5) CAT scrapers (model 657E) working
in a continuous short haul cycle long the eastern alignment limit, two (2) CAT dozers
(model D9R), a CAT dozer (model n/a), and water truck.
Testing conditions. during the monitoring intervals were clear with an average
barometric pressure reading of 30.05 in-Hg, an average westerly wind speed of 0 to 5
miles per hour (MPH), and an approximate mean temperature of 85 degrees
Fahrenheit. The results of the sound level monitoring are shown below in Table 1. The
values for the energy equivalent sound level (Leq), the maximum and minimum
measured sound levels (Lmax and Lmin), and the statistical indicators L10, L50, and
L90, are given for each monitoring location. Areas in excess of the i30-dBA Leq-h
impact threshold are underlined.
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #21 (8-26-99)
ISE Report #99-009u, 035
August 27, 1999
Page 6
Table 1: Measured Construction Levels - Cannon Road Alignment
I
Site Leq.
1-Hour NoiseLeve!.Descriptors in dBA
Lmax Lmin .LiO .1-50 L90
9:00 a.m.
ML 1 51.0 74.0 47.5 49.5 48.5 48.0
ML 2 54.0 70.0 43.0 57.0 52.0 47.0
ML 56.0 74.0 41.0 59.0 55.0 49.0
ML 4 53.0 76.0 38.5 52.5 42.0 40.0
10:00 a.m.
MI-1 50.5 71.0 48.0 51.0 49.0 48.5
ML 2 51.5 74.5 41.0 52.5 48.5 44.5
MI-3 58.0 79.5 43.5 59.5 55.0 49.0
MI-4 54.0 75.5 39.5 51.0 42.5 40.5
11:00 a.m.
ML 1 49.5 72.5 46.5 52.5 50.5 49.0
ML 53.5 72.0 41.5 54.5 48.5 45.0
MI-3 57.5 79.0 43.5 59.5 56.0 51.0
MI-4 58.5 87.5 40.5 65.5 55.5 46.5
12:00 p.m.
ML 1 53.5 725 47.5 54.5 50.0 48.5
MI-2 54.0 73.5 42.5 55.5 49.5 46.0
MI-3 57.5 73.0 44.5 59.5 55.5 51.0
ML 60.5 76.0 .46.0 66.0 56.5 52.0
1:00 P.M.
ML 1 52.5 71.5 46.5 53.5 51.0 49.5
ML 2 54.5 79.5 39.0 51.5 45.5 42.0
ML 3 58.5 80.0 44.5 60.5 57.0 52.0
ML 4 57.5 84.5 39.5 64.5 54.5 45.5
Measurements collected at monitoring locations, ML 1 through ML 4, reflect
typical sound levels associated with the community setting observed and the
topography of the surrounding terrain. With the exception of location ML 4 (Macano
Canyon), all monitoring stations were below the 60-dBA Leq-h impact threshold during
the Week #21 monitoring period. The highest hourly energy equivalent sound level
(Leq-h) recorded for monitoring locations ML 1 through 3 was 58.5 dBA and was due
Mr. Doug .Gettinger
Cannon Road Mitigation Monitoring Results - Week #21 (8-26-99)
ISE Report #99-009u, 035
August 27, 1999
Page 7
entirely to traffic activity along El Camino Real. Additionally, the highest Leq-h recorded
at monitoring location ML 4 was 60.5 dBA. The exceedance recorded at ML 4 during
the 12:00 p.m. monitoring' interval was due to the close proximity of equipment
staging/idling to the habitat.
Finally, the background noise level (L90) for the Macano Canyon monitoring
station (ML 4) never exceeded 52.0 dBA thus enabling vireo communication over 90
percent of any stated time interval.
EM Recommendations
With the exception of ML 4 (Macano Canyon), All monitoring locations were
observed to be below the 60-dBA Leq impact threshold throughout the duration of the
Week #21 monitoring period. The exceedances recorded at ML 4 were attributed to the
close proximity of equipment staging/idling to the habitat boundary. The following
mitigation measures are recommended.
Idling of equipment should be kept to a minimum, especially in areas
immediately adjacent to the habitat of concern.
Staging and maintenance of equipment should be performed away from the
habitat boundary.
Should you have any questions regarding the above conclusion, please do not
hesitate to contact me at (619) 640-9379.
Sincere ,
Rick Tavares, REA, INCE
Project Principal
Investigative Science and Engineering
Cc: Shem Howard, City of Carlsbad
Glen Laube, ISE
i
Investigative Science and Engineering
3511 Carnino Del Rio South, Suite 302 Phone,Fax: 619-640-9379 /619-640-0763
San Diego, CA 92108-4003 www.ise-advantage.com
August 23, 1999 RECEIVED
Mr. Doug Gethnger AUG 25 1999
Ogden Environmental and Energy, Inc.
5510 Morehouse Drive ENGINEERING
San Diego, CA 92121 DEPARTMENT
Re: Cannon Road Mitigation Monitoring Results - Week #20 (8-20-99)
(ISE Report #99-009t, 035)
Dear Mr. Gettinger:
Pursuant to U.S.F.W.S. permit approval requirements, Investigative Science
and Engineering (lSE) has examined potential noise impacts to the riparian habitat
along the proposed Cannon Road extension alignment located in Carlsbad, California.
A field survey of the site was performed on August 20, .1999. The results of that survey
are presented in this letter report.
ES Introduction and Definitions
Site Characterization
The Cannon Road West Project is located in the City of Carlsbad in San Diego
County, California (refer to Figure 1). This project will extend Cannon Road
approximately 2 miles east from its terminus at 1-5 to El Camino Real. The Cannon
Road extension consists of two bridge crossings and traverses through and adjacent to
habitat for the federally endangered/threatened least Bell's vireo, southwestern willow
flycatcher, and California gnatcatcher.
The predominate land use of the project area is undisturbed open space.
Wetlands originating from the Agua Hedionda Lagoon and Agua Hedionda Creek are
located adjacent to the north and commercial developments are present to the west.
Elevations for the project area have been altered due to construction activities;
however, pre-construction elevations range from approximately 100 feet above mean
sea level (MSL) along the terrace over looking Agua Hedionda Lagoon down to
approximately 5 feet above MSL along the banks of the Agua Hediorda Creek.
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Mr. Doug Gettinger .•
Cannon Road Mitigation Monitoring Results —Week #20 (8-20-99)
ISE Report #99-009t, 035 ;, . ..4
* August 23, 1999 -
Page 2
-
14
I
1
Figure 1: Project Alignment Area, Map (Thomas Guide Pages 1126,1127, and 1107)
Acoustical Definitions
- . - '•'•. .. - s. -. , . '
Airborne sound is .à rapid fluctuãtiôn of
- air, pressure above and below
* '
- atmospheric levels. The loudest sounds the human ear can hear conformably is
, *
- S
- approximately one trillion (a one with 12 zeros following it) times the acoustic energy
-' - that the ear can barely detect. Because of this vast range, any attempt to represent the
acoustic intensity of a particular sound on à'linear scale becomes unwieldy. Becauseof
- this, a logarithmic ratiO known as the decibel (dB) is commonly employed. A sound levelS -.
of zero "0" dB is scaled such that-it is defined-as the threshold of human hearing and
, would be barely audible to a human of normal hearing under extremely quiet listening- -
- conditions and would correspond to a sound pressure level equal-to the reference level.'
- - - Most of the sounds we hear in the,envirohmertdo not consist of.a single
- '.- frequency, but rather a broad band of frequencies differing in sound level. The
-
- , intensities of each frequency add to gehérate the sound we hear. The method
commonly used to quantify environmental sounds consists, of determining all of the
frequencies of a sound according to a weighting system that reflects the nonlinear -
. response characteristics of the human ear. This is called "A" weighting, and the decibel -:
,. . level measured is called the A-weighted sound level (or dBA). In practice, the level of a'-
noise source is conveniently measured usinga sound level meter that include's a filter *
corresponding to the dBA curve
Although the A-weighted sound level rna 'adequately indicate the level of
environmental noise at any instant in- time, community noise .levels vary continuously.
.-. ''
:' - .1.f ' - - .•
- --
.4- 5 - *
I
-
_
S ,),, •.
,
, .
5,-. '. -- ,
- :, - - - . -: -S-" -'
5
. S
-
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results -Week #20 (8-20-99)
ISE Report #99-009t, 035
August 23, 1999
Page
Environmental noise includes a conglomeration of sounds from distant sources that
create a relatively steady background noise in which no particular source is identifiable.
For this type of noise, a single descriptor called the Leq ((Sr equivalent sound level) is
used. Leq is the energy-mean A-weighted sound level during a measured time interval.
It is the 'equivalent' constant sound level that would have to be produced by a given
source to equal the fluctuating level measured.
To describe time-varying character of environmental noise, the statistical noise
descriptors L10, L50, and L90 are commonly used. They are the noise levels equaled
or exceeded during 10 percent, 50 percent, and 90 percent of a stated time. Sound
levels associated with the LIO typically describe transient or short-term events, while
levels associated with the L90 describe the steady state (or most prevalent) noise
conditions. In addition, it is often desirable to know the acoustic range of the noise
source being measured. This is accomplished through the maximum and minimum
measured sound level (Lmax and Lmin) indicators. The Lmin value obtained for a
particular monitoring location is often called the acoustic flOor for that location.
Applicable Significance Criteria
Wildlife Habitat Regulations
Construction and operational noise generated by this project is regulated by the
United States Fish and Wildlife Service (U.S.F.W.S.) and the California Department of
Fish and Game for its effect on federally endangered least Bell's vireo (Vireo be//il
pusillus) and the southwestern willow flycatcher (Empidonax trail/fl extrimus) and the
federally threatened California gnatcatcher (Polioptila california).
Resource agencies have theorized that elevated noise levels can potentially
mask songs of the least Bell's vireo which are used to attract mates and defend
territories. The San Diego Association of Governments (SANDAG) in a 1990 study
entitled "Comprehensive Species Management Plan for the least Bell's vireo"
theoretically estimated that {traffic} noise levels above 60 dBA Leq in vireo breeding
areas may sufficiently mask the vireo's song and potentially reduce the reproductive
success of this species during their breeding season that occurs from March 1 to
September 1. Since sustained noise exposure (indicated by the L90 metric) produces
greater masking effects than intermittent peak levels, this report will analyze both
effects. The SANDAG report conclusions were unclear as to the specific time interval of
the measurement, but it is typically taken as one hour. Although research is on going
regarding similar noise impacts to the southwestern willow flycatcher and California
gnatcatcher, in the absence of species-specific data, these same study results are
applied by the Service to this bird species as well.
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #20 (8-20-99)
ISE Report #99-009t, 035
August 23, 1999
Page 4
Analysis Methodology
Existing Conditions Field Survey
Four Larson Davis Model 700 ANSI Type 2 integrating sound level meters were
used as the data collection devices. The meters were positioned at the locations shown
below in Figure 2 and the accompanying matrix.
intor
IVIL
.-,---.--..----.----
/ S.
357/Jf
\
0 1/2 1MILE TN 1' i !vIN I
/ 13Y.0 (I 1000 0 1000 2000 3000 4000 FEET I -I
Figure 2: Project Area Topography (USGS 7.5 San Luis Rey Quadrangle 1:12000)
Monitor Sta. Eng. Sta. No. GPS Làt GPS.Lon Description
ML #1 102+00 330 08.780 N 1170 18.195W Western end of alignment
ML #2 113+00 330 08.826 N 1170 18.011 W Central point of alignment
ML #3 n/a 330 08.952 N 1170 17.895W Eastern end of alignment
ML #4 n/a 330 08.194 N 1170 18.401 W Macario Canyon Area
EPE = Estimated Position Error = 49'
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #20 (8-20-99)
ISE Report #99-009t, 035
August 23, 1999
Page
The meters were mounted on tripods roughly 5 feet above the ground and were
calibrated before and after each field deployment. Each station was programmed to
record and log the following noise metrics each hour: Leq-h, Lmax, Lmin, L10, L50, and
L90. Ix-
Field Monitoring Results
A field survey was performed to ascertain construction noise levels within the
habitat area due to excavating, bridge fabrication, light grading and associated ancillary
activities. To date, the least Bell's vireo has been predominantly located between
station markers 103+00 and 108+00. These station markers correlate. with ISE
monitoring locations I and 2. Additional sightings of the least Bell's vireo have been
observed within Macario Canyon (approximately 1-mile southwest of ISE monitoring
location ML 1) and in the 1/4 acre habitat located between the El Camino Real / Cannon
Road access bridge and the haul road entrance (approximately 300 feet south of ISE
monitoring location ML 3).
During the Week #20 monitoring period, no construction activities associated
with the Cannon Road West Project were identified. Activities and equipment observed
at Macario Canyon were associated with connection of the Faraday haul road to the
Cannon Road alignment and included a single CAT dozer (model n/a), and water truck.
Testing conditions during the monitoring intervals were clear with an average
barometric pressure reading of 30.05 in-Hg, an average westerly wind speed of 0 to 3
miles per hour. (MPH), and an approximate mean temperature of 80 degrees
Fahrenheit. The results of the sound level monitoring are shown below in Table 1. The
values for the energy equivalent sound level (Leq), the maximum and minimum
measured sound levels (1-ma and Lmin), and the statistical indicators L10, L50, and
L90, are given for each monitoring location. Areas in excess of the 60-dBA Leq-h
impact threshold are underlined.
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #20 (8-20-99)
ISE Report #99-009t, 035
August 23, 1999
Page
Table 1: Measured Construction Levels - Cannon Road Alignment
I 1-Hour Noise Level. Descriptors indBA 1:
Site '.'Leg. Lmax Lmin LIO L50 L90
9:00 a.m.
ML 1* n/a n/a n/a n/a n/a n/a
MI-2 51.0 69.5 46.0 52.5 48.0 47.0
MI-3 54.5 74.0 42.0 57.0 53.0 47.5
ML 4 53.0 76.0 38.5 52.5 42.0 40.0
10:00 a.m.
ML 1* n/a n/a n/a n/a n/a n/a
MI-2 51.5 61.5 47.0 54.5 49.5 48.0
ML 54.0 61.5 41.5 57.0 53.5 49.0
MI-4 57.5 68.0, 39.5 60.5 56.5 41.5
11:00 a.m.
ML 1* 5 n/a n/ n/a n/a n/a n/a
MI-2 51.5 68.0 47.0 54.5 50.0 48.0
ML 3 54.5 63.0 42.5 57.5 54.0 48.5
MI-4 47.5 65.5 39.5 50.0 42.0 40.5
12:00 p.m.
ML 1* n/a n/a n/a n/a n/a n/a
ML 2 53.0 69.5 47.0 55.0 50.0 48.0
MIL 55.5 71.5 43.0 58.0 54.0 49.5
MI-4 55.0 75.5 5 39.5 56.5 43.0 41.0
1:00 P.M.
ML 1* n/a n/a n/a n/a n/a n/a
ML 2 53.5 68.5 47.0 58.0 49.5 47.5
MI-3 56.0 71.0 42.0 58.5 55.0 50.0
ML 4 54.5 75.0 39.5 56.0 44.0 40.5
*: ML 1 data not available due to theft of equipment
Measurements collected at monitoring locations, ML 1 through ML 4, reflect
typical sound levels associated with the community setting observed and the
topography of the surrounding terrain. Measurements for monitoring location ML 1 were
not available for the Week #20 monitoring period due to theft (i.e., the monitoring
equipment was stolen off the jobsite). All remaining monitoring stations were below the
60-dBA Leq-h impact threshold during the Week #20. monitoring period. The highest
Mr. Doug Gettinger
Cannon Road Mitigation Monitoring Results - Week #20 (8-20-99)
ISE Report #99-009t, 035
August 23, 1999
Page
hourly energy equivalent sound level (Leq-h) recorded for monitoring locations ML 1
through 3 was 56.0 dBA and was due entirely to traffic activity along El Camino Real.
Additionally, the highest Leq-h recorded at monitoring location ML 4 was 57.5 dBA.
These levels are lower than in previous weeks due to discussions between ISE, City
staff, and the project foreman on methods to reduce the exceedance.
Recommendations
All monitoring locations were observed to be below the 60-dBA Leq impact
threshold throughout the duration of the Week #20 monitoring period. ISE recommends
no further mitigation at this time.
Should you have any questions regarding the above conclusion, please do not
hesitate to contact me at (619) 640-9379.
Sincerely,
Rick Tavares, REA, INCE
Project Principal
Investigative Science and Engineering
Cc: Sherri Howard, City of Carlsbad
Glen Laube, ISE
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