HomeMy WebLinkAboutCT 02-07; EMERALD POINT ESTATES; ACOUSTICAL EVALUATION STUDY; 1998-04-24OGDEN • --
ENI/IRO/V/v!ENTAL A/'vD ENERGY' SERVICES ... ~ ~ ................................................ .
April 24, 1998
98-233-3151
Mr. Tony Hummel
Newport Financial Center
1303 Avocado Avenue, Suite 245
Newport Beach, California 92660
5510 Ai'ors/.::7f..:'Se [Jr.
Sa!7 Die[/o, CA 92 j'2:'
619458904.:/.
Fax 619 458 0943
Re: Acoustical Evaluation Study -BCS Emerald Pointe Estates (APN #'
212-040-50)
Dear Mr. Hummel:
At the request of Jack Henthorn and Associates, Ogden Environmental and Energy
Services Inc. (Ogden) was directed to investigate potential noise impacts from the
development of the proposed BCS Emerald Pointe Estates located in Carlsbad, California.
An acoustical survey of the site was performed on December 23, 1997. The results of that
survey, as well as predicted future sound levels at the site, are presented in this Jetter
report.
Introduction and Definitions
Existing Site Characterization
The project site consists of 18.02 acres within the incorporated area of the City of
Carlsbad. The site is located approximately 1,000 feet south of Palomar Airport Road and
1,300 feet east of (the future alignment of) College Boulevard. The project site consists
primarily of undisturbed and disturbed open space. No existing structures are located
onsite.
A gently sloping mesa from south to north surrounded by steep slopes characterizes the
topography of the site. A small depression is located in the southwes~ portion of the
property near the edge of the mesa. The area proposed for development.1s located on the
mesa top in the southeastern portion of the site; the northwestern portion of the site consists
of steep, north-and west-facing slopes, and is proposed for open space. Encinas Creek, a
small intermittent stream, is located directly north of the property at the base of the slope.
Elevations onsite range from approximately 100 feet above mean sea level (or MSL) at the
base of the slope to 260 feet MSL on the southeastern portion of the mesa.
Land -uses surrounding the site range from residential to industrial. North of the site is
agricultural land and open space. McClellan-Palomar Airport and associated .industrial uses
are located to the northeast. To the south, east and west of the site are 'areas proposed, for
residential development. The area directly east of the property is currently being
developed, while the areas to the south and west are scheduled for development in late
l\1r. Tony Hummel
April 24, 1998
Page 2
•
1998. Construction activities associated with the extension of College Boulevard and
proposed residential development are currently located west of the site.
Acoustical Definitions
Noise is generally defined as unwanted or annoying sound that is typically associated with
human activity and which interferes with or disrupts nonnal activities. Although exposure
to high noise levels has been demonstrated to cause hearing loss, the principal human
response to environmental noise is annoyance. The response of individuals to similar noise
events is diverse and influenced by the type of noise, the perceived importance of the noise
and its appropriateness in the setting, the time of day, and the sensitivity of the individual
hearing the sound.
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. As a result 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 environmentaJ.
noise at any instant in time, community noise levels vary continuously. Most 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 flqise
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
LI0, 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 LlO 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.
NIr. Tony Hummel
April 24, 1998
Page 3
Another sound measure employed by the State of California is known as the Community
Noise Equivalence Level (or CNEL) is defined as the "A" weighted average sound level for
a 24-hour day. It is calculated by adding a 5 decibel penalty to sound levels in the even.ir).g
(7:00 p.m. to 10:00 p.m.), and a 10 decibel penalty to sound levels in the night (10:00
p.m. to 7:00 a.m.) to compensate for the increased sensitivity to noise during the quieter
eve~ng and nighttime hours. .
Applicable Significance Criteria
City of Carlsbad
The Noise Element of the City of Carlsbad identifies sound levels that are cot.p.patible with
various land uses. According to the City of Carlsbad Draft Noise Guideliries Manual,
sound levels up to 60 dBA CNEL are compatible with residential land uses. Sound levels
up to 65 dB A CNEL are compatible with recreational areas such as parks and
playgrounds.
State of California
The California Code of Regulations (CCR), Title 24, Noise Insulation Standarqs, states
that multi-family dwellings, hotels, and motels located where the CNEL exceeds 60 dBA,
must obtain an acoustical analysis showing that the proposed design will limit interior nOIse
to less than 45 dBA CNEL. Worst case noise levels, either existing or future, must be
used for this determination. Future noise levels must be predicted at least ten years from
the time of building permit application. The City of Carlsbad has accepted the CCR Title
24 standards.
Analysis Methodology
Existing Conditions Survey
Two Larson Davis Model 700 ANSI Type 2 integrating sound level meters were used as
the data collection devices. The meters were placed at the midpoint of rear lot lines for
proposed pad locations No. 13 (ML 1) and No. 8 (ML 2) as identified on the project map
(Emerald Pointe Estates -BRA Inc -November 20,1997). The meters were mounted on a
tripod five feet above the ground in order to simulate the average height of the human ear
above ground. The measurements were performed on December 23, 1997. The sound level
meters were calibrated before and after each set of measurements. All sound measurement
equipment was within the valid manufacturers calibration period.
Future Acoustical Environment
The primary source of noise in the vicinity of the project in the year 2015 would be from
Palomar Airport Road. The 2015 ADT along this road is projected to be 36,000 vehicles
directly adjacent to the parcel (Source: SANDAG Series 8 projections). The future traffic
speed along this arterial roadway will be 55 MPH (Source: SANDAG). Peak hour traffic
values are calculated for a 10% traffic flow pattern and a 93.7/4.112.2
(automobiles/medium!heavy vehicles) percent mix (Source: Caltrans).
Mr. Tony Hummel
April 24, 1998
Page 4
To a lesser extent, traffic activity along the proposed College Boulevard extension and local
collector Cobblestone Road will impact the project site. The 2015 ADT along College
Boulevard is anticipated to be 12,000 vehicles at a speed of 50 MPH. The future ADT
along Cobblestone Road is expected to be 2,130 vehicles at a speed of35 MPH. Peak hour
traffic values along these roads were calculated for a worst-case scenario of 10% of the
ADT with a mix of 93.7/4.112.2 and 98/1/1 for the two roads respectively. It should be
not.ed that the existing Laurel Tree Road is not included in the analysis since it is being
replaced by the College Boulevard extension. Thus, no future projections ate available for
this roadway.
The Caltrans Sound 32 Traffic Noise Prediction Model with California (CAL VENO) noise
emission factors (based on FHW A RD-77 -108 and FHW NCA/TL-87 /03 standards) was
used to calculate future onsite vehicular traffic noise levels. Model input included a digitized
representation of the adjacent roadway alignments, site topography, ADT, vehicle speed,
vehicle mix, and receptor elevations. The roadway and site topography elevations were
obtained from the site grading plans. (BRA Inc., 1997)
Receptor elevation was considered to be S feet above the appropriate floor elevation. The
model assumed a "hard" site sound propagation rule (Le., a 3-dBA loss per doubling of
distance). The model also considered the attenuation due to the slope adjacent to the project
site. Future noise levels were calculated for the first and second floor (assumed to be 20
feet above the building pad) elevations.
Findings
Ambient Sound Measurement Results
Testincr conditions during the monitoring period were clear and sunny with an average barom~tric pressure reading of29.90 in-Hg, an average south-southwesterly wind speed of
1 to 3 miles per hour (MPH), and an approximate mean temperature of. 68 degrees
Fahrenheit. The results of the sound level monitoring are shown below in Table 1. The
values for the equivalent sound level (Leq), the maximum and minimum measured sound
levels (Lmax and Lmin), and the statistical indicators LlO, LSO, and L90, are given for
each monitoring location.
Mr. Tony Hummel
April 24, 1998
Page 5
Table 1: Measured Ambient Sound Levels at the BCS Emerald Pointe
Estates
I-Hour Noise Level Descriptors in dBA
Site Start Time Leq Lmax Lmin LlO L50 L90
NIL 1 7:30 a.m. 60 68.5 51.5 62.5 60 57
NIL 1 7:30 a.m. 59 68.5 52 61.5 59 56
Iv1L2 8:30 a.m. 61.5 71 53 64 61 57
NIL 2 8:30 a.m. 59.5 69.5 49 62.5 59 55.5
Monitoring Locations:
• ML 1: Meter positioned at Lot No. 13. Meter facing due north (0° Azimuth).
• ML 2: Meter positioned at Lot No.8. Meter facing due north (0° Azimuth).
Measurements performed by Ogden Environmental on December 23, 1997.
Measurements collected at monitoring locations ML 1 and ML 2 reflect typical sound levels
associated with the community setting observed and the topography of the surrounding
terrain. The hourly energy average sound levels (or Leq-h) recorded over the monitoring
periods differed by only two decibels. This was due to the relative isolation and the
consistency of the traffic flow adjacent to the project site. As indicated by the monitoring
equipment, at least 90 percent of the time the sound level averaged between 55.5 to 57.0
dBA. The difference between the Leq and L90 metrics was directly attributable to
automobile traffic along Palomar Airport Road and aircraft activity since the Leq indicator
contains the contribution of automobile noise (oflevels equal to the Lmax) whereas the L90
indicator does not. The acoustic floor for the site, as seen by the Lmin indicator was
moderate (average of approximately 51 dBA for the two locations monitored) and reflects
the semi-rural nature of the project site.
Design Year 2015 Impacts
The results of the acoustical rriodeling are shown below in Table 2. Based on the model
results, future noise levels from vehicular traffic were calculated to be as high as 53 dBA
CNEL at first floor elevations and 61.3 dBA CNEL at second floor elevations. These
"traffic only" projections are lower than those currently measured at the project site due to
the presence of nearby transportation noise sources.
Mr. Tony Hummel
April 24, 1998
Page 6
Table 2: Acoustical Modeling Results -BCS Emerald Pointe Estates
ReceptorID Ground Upper Level
Level
ReceptorID Ground Upper Level
Level
Rl 53.4 57.2 RI4 52.8
R2 50.7 56 RI5 52.4
R3 46.7 54.6 R16 52.1
R4 46 54.2 RI7 50.9 59.2
R5 45.8 54 RI8 56.2 58.5
R6 47.4 54.3 RI9 50.7 58
R7 46.2 54.2 R20 50.3 57.4
R8 45.9 54.3 R2I 51.5 56.7
R9 46.8 54.4 R22 48.7 55.9
RlO 47 54.6 R23 48.2 55.2
Rll 47.1 55.2 R24 56 56,1
R12 51.5 60 R25 44.9 52.5
R13 53 61.3 '. R26 44.4 49.8
Modeled using the Caltrans Sound 32 Traffic Noise Prediction Model with California
(CAL VENO) noise emission factors (based on FHW A RD-77-108 and FHW AlCAffL-
87/03 standards).
Darkened areas indicate levels above established threshold criteria.
Aircraft Transr;1ortation Noise Sources Identified
The project site lies within the influence areas of McClellan-Palomar Airport and associated
industrial uses to the northeast. The project site is located between the 60 and 65 dBA
CNEL aircraft noise contours for the airport. The airport is currently operating at fun
capacity (maximum typical number of flight operations per day) and thlis no appreciable
increase in the contours is expected within the project analysis horizon.
Conclusions
The following conclusions regarding acoustical impacts at the BCS Emerald Pointe Estates
are made:
1. Future ground-level traffic noise impacts at the project site were found to be
below the significance threshold as defined by the City of Carlsbad (e.g., 60
dBA CNEL). Thus, exterior mitigation in the form of noise walls or perimeter
screens would not be required.
•
Mr. Tony Hummel
April 24, 1998
Page 7
2. Future second-story traffic noise impacts at the project site were found to be
above the significance threshold as defined by the City for Lots 12 through 16.
Thus, units built upon these lots would require interior acoustical compliance in
accordance with CCR Title 24 Standards.
3. The project area lies between the 60 and 65 dBA CNEL aircraft noise contours
for the McClellan-Palomar Airport. Thus, all units bullt upon these lots would
require interior acoustical compliance in accordance with CCR Title 24
Standards (i.e., dual-paned windows and/or specialized acoustical treatments).
Should you have any questions, please feel free to contact me at (619) 458-9044 Extension
308.
Sincerely,
/q/ ;:;~5
Rick Tavares, EIT, REA, INCE
Civil Engineer, Acoustics and Vibration Group
RT/alo
cc: John Conley, Ogden
Melissa Allen, Jack Henthorn & Associates
Contract #3-1884-1000-0000-3151