HomeMy WebLinkAboutCT 98-14; Thompson/Tabata; Tentative Map (CT) (109)Investigative Science and Engineering, Inc.
3545 Cam/no Del Rio South, Suite E Phone/Fax: 619-640-9379 / 619-640-0763
San Diego, C/A 92108-4003 www.investigative-science.com
January 2, 2001 (Revised)
Ms. Kathy Baker
Standard Pacific Homes
5750 Fleet Street, Suite 200
Carlsbad, CA 92008
Re: Standard Pacific Poinsettia Property Acoustical Study (ISE Report #98-017)
Dear Ms. Baker:
At the request of Standard Pacific Properties, Investigative Science and
Engineering (ISE) was directed to investigate potential noise impacts to the proposed
Poinsettia Properties residential development located in Carlsbad, California. An
acoustical survey of the site was performed on August 27, 1998. The results of that
survey, as well as predicted future sound levels at the site, are presented in this letter
report.
Introduction and Definitions
Existing Site Characterization
The project site consists of 82.2 acres located in the central portion of the City of
Carlsbad in San Diego County, California (refer to Figure 1). The site resides on both
sides of Poinsettia Lane, approximately one mile east of Interstate 5. The lots are bound
by Aviara Parkway to the east, single-family residential housing to the north, and high-
density single-family housing to the west and south. The project site appears to have
been rough graded for existing agricultural and nonagricultural operations. Existing land
uses on the property include tomato fields on the eastern terraced side of the property,
and undeveloped open space. The property contains two structures, both of which are
single-family homes. In addition, two access roads are located on the project site to the
south of Poinsettia Lane. The first road parallels the western boundary of the project site
connecting Poinsettia Lane to the existing nursery, while the second connects Poinsettia
Lane to the upper portion of the property. The site is currently zoned L-C and R-1-10000
with a proposed zoning of R-1-7500 and RD-M-Q.
The eastern portion of the project site contains moderate westward facing slopes
while the western half of the site contains gentle slopes with minor relief (refer to Figure
2). Elevations on the site range from approximately 308 feet above mean sea level
(MSL) at the northeastern portion of the property to approximately 195 feet MSL at the
southwestern corner of the property.
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
Page 2
Figure 1: Project Vicinity Map (Thomas Guide Page 1127, Grid B5)
Acoustical Definitions
Noise is generally defined as unwanted or annoying sound that is typically
associated with human activity and which interferes with or disrupts normal 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. 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.
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
PageS
Figure 2: Project Area Topography (USGS 7.5 Encinitas Quadrangle 1:12000)
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.
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 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
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
Page 4
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.
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 evening (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 evening and nighttime hours.
Applicable Significance Criteria
City of Carlsbad
The Noise Element of the City of Carlsbad identifies sound levels that are
compatible with various land uses. According to the City of Carlsbad Draft Noise
Guidelines Manual, sound levels up to 60 dBA CNEL are compatible with residential
land uses. Sound levels up to 65 dBA CNEL are compatible with recreational areas
such as parks and playgrounds. The City also requires an interior noise study (compliant
with State of California CCR Title 24 standards) where exterior exposure is in excess of
the above land use criteria.
Rear and side yard areas of the proposed Poinsettia Property development
would be classified as usable exterior living space; thus, the City's guidelines will be
applied in this report to determine the requirement of exterior and interior mitigation at all
proposed units within the development adjacent to Poinsettia Lane and Aviara Parkway.
There is no proposed usable exterior space within the affordable housing development
area.
State of California CCR Title 24
The California Code of Regulations (CCR), Title 24, Noise Insulation Standards,
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.
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
PageS
Analysis Methodology
Existing Conditions Field Survey
A Larson Davis Model 700 ANSI Type 2 integrating sound level meter was used
as the data collection device. The meter was placed at the following locations: along
Poinsettia Lane at the southwestern corner of Lot #94 (ML 1); along Poinsettia Lane
opposite from proposed 'A' Street intersection (ML 2); and, overlooking intersection of
Aviara and Poinsettia on Lot #7 (ML 3). The meter was mounted on a tripod roughly 5
feet above the ground in order to simulate the average height of the human ear above
ground. The measurements were performed on August 27, 1998. The sound level meter
was calibrated before and after each set of measurements.
Future Acoustical Environment Modeling
The Caltrans Sound 32 Traffic Noise Prediction Model with California
(CALVENO) noise emission factors (based on FHWA RD-77-108 and FHWA/CA/TL-
87/03 standards) was used to calculate future onsite vehicular traffic noise levels. Model
input included a digitized representation of the alignment of Poinsettia Lane and Aviara
Parkway, as well as any local site topography, future ADT volume, vehicle mix, and
receptor elevations. The roadway and site topography elevations were obtained/verified
from the project site plan (Source: Standard Pacific Poinsettia Property TM - Buccola
Engineering - 9/1/00). Model output consisted of peak hour energy-mean A-weighted
sound levels (or Leq-h) for each receptor examined.
Receptor elevations were considered 5 feet above the appropriate floor (pad)
elevation. The model assumed a "hard" site sound propagation rule (i.e., a 3-dBA loss
per doubling of distance from roadway to receiver) in accordance with Caltrans
practices. 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 elevations
(assumed to be five and 20 feet respectively above the building pad).
Findings
Ambient Sound Measurement Results
Testing conditions during the monitoring period were partly cloudy with an
average barometric pressure reading of 29.85 in-Hg, an average northerly wind speed of
3 to 5 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 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.
Measurements collected at monitoring locations ML 1 through ML 3 reflect typical
sound levels associated with the community setting observed and the topography of the
surrounding terrain. The onsite hourly energy average sound levels (or Leq-h) recorded
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
Page 6
at 50 foot setback points along the edge of Poinsettia Lane was fairly constant over the
three consecutive hours monitored. As indicated by the monitoring equipment, at least
90 percent of the time the onsite sound level averaged between 44 and 52 dBA. The
difference between the Leq and L90 metrics was directly attributable to the intermittent
nature of automobile traffic along Poinsettia Lane during morning peak hour conditions.
The acoustic floor for the site, as seen by the Lmin indicator was low (between 38 and
46 dBA for all locations monitored) and reflects the semi-rural community noise
environment of the project site.
TABLE 1: Measured Ambient Sound Levels - Standard Pacific Poinsettia Property
1-Hour Noise Level Descriptors in
Site Start Time Leq Lmax Lmin L10 L50 • L90
ML1
ML 2
ML 3
6:00 a.m.
7:00 a.m.
8:00 a.m.
57.3
57.4
58.3
67.5
70.0
72.0
38.0
41.0
45.5
61.0
60.5
61.0
54.5
55.0
56.5
43.5
46.0
51.5
Monitoring Locations:
o ML 1: Meter positioned along Poinsettia Lane at the southwestern corner of Lot #94
o ML 2: Meter positioned along Poinsettia Lane opposite from proposed 'A1 Street intersection
o ML 3: Meter positioned overlooking intersection of Aviara and Poinsettia on Lot #7
All positions taken at an approximate 50 foot setback from the edge of Poinsettia Lane
Measurements performed by ISE on August 27,1998.
Future Traffic Noise Impacts
The primary source of future traffic noise near the project would be from
Poinsettia Lane. Future year 2010 volume along this roadway alignment is projected to
be 36,000 ADT traveling at the posted speed of 40 MPH (Source: Traffic Impact Analysis
- Thompson Property - Carlsbad CA, LLG Engineers, 12/6/00). The projected year 2010
ADT for adjacent Aviara Parkway is 19,000 with a posted speed of 40 MPH.
Peak hour traffic values are calculated for an 8% traffic flow pattern and a 98/1/1
(automobiles/medium/heavy vehicles) percent mix in accordance with Caltrans traffic
forecasting practices. For peak hour traffic percentages between approximately 8 and 12
percent (and a Level of Service, or LOS, between A through C) the energy-mean A-
weighted sound level is equivalent to the 24-hour Community Noise Equivalent Level
(CNEL). Outside this range, a maximum variance of up to two dBA occurs between Leq-
h and CNEL.
The results of the acoustical modeling are shown below in Table 2. Values for
selected pad locations adjacent to Poinsettia Lane and Aviary Parkway are given. Also
shown are the predicted noise levels for 1) unmitigated ground floor areas, 2) mitigated
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
Page 7
ground floor areas, and 3) mitigated second floor levels. Based on the model results,
some lots adjacent to Poinsettia Lane and Aviara Parkway were found to be above the
60 dBA CNEL threshold criteria established by the City.
TABLE 2: Acoustical Modeling Results- Standard Pacific Poinsettia Property
. Ground Ground Second
. L0,. Level Level FloorLocation {Unm|t) (m) Aregs
1 56.1 52.2 59.4
2 57.2 53.6 62.2(1)
3 60.5 56.0 67.7(1)
4 58.3 54.5 63.2(1)
5 61.3 56.9 67.9(1)
6 60.2 58.1 67.6(1)
8 60.8 56.7 63.9(1)
9 59.3 56.6 59.9
13 57.4 57.3 57.3
17 55.3 55.1 55.1
60 68.1 56.9 65.4(1)
Affordable 57.3- n/a 58.5-
Housing 65.3 65.7(1)
203 65.5 59.5 66.5(1)
204 66.8 59.1 67.5(1)
213 63.3 57.6 66.0(1)
214 67.0 58.9 67.2(1)
•
, . Ground. Ground 7; Second
i«,.f<L., Level teVetvV FloorLocation {Unmit.) v ;)^p)i^. Areas-
215 67.4 59.4 67.6(1)
216 67.3 59.2 67.4(1)
217 66.6 58.4 66.7(1)
218 65.6 59.1 65.7(1)
219 63.2 58.0 63.6(1)
225 57.2 57.2 64.1(1)
226 55.8 55.8 63.8(1)
227 55.3 55.2 63.2(1)
228 55.5 55.4 63.6(1)
230 58.4 54.7 63.2(1)
231 58.3 54.3 62.0(1)
232 58.1 54.1 62.0(1)
233 60.2 55.3 65.2(1)
234 62.4 56.5 65.6(1)
235 61.6 56.8 64.3(1)
236 52.8 50.2 56.0
Notes:
o Values represent a sampling of potentially impacted lots along Poinsettia Lane and Aviara Parkway
Lots 'sandwiched' between the lots shown above would also require the same treatment,
o Modeled using the Caltrans Sound 32 Traffic Noise Prediction Model with California (GALVENO)
noise emission factors (based on FHVVA RD-77-108 and FHWA/CA/TL-87/03 standards).
o Levels denoted with (I) indicate the requirement (or potential for; requirement) of interior noise
mitigation. ! :L "•'••-. ' /•
o All sound levels given in dBA CNEL.
Lots numbered 3 though 8, 60, 61, the affordable housing area, 203, 204, 213
through 219, and 231 though 236 were found to have projected future (ground level)
traffic-related noise levels in excess of the 60 dBA CNEL threshold established by the
City. Except for the affordable housing area, which has no usable exterior space, these
lots would require noise walls ranging from five to seven feet to be located along the rear
property line between Poinsettia Lane and the residential receptor. A schematic of the
proposed wall design is shown in Figure 3 as an attachment to this report. Projected
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
PageS
traffic volumes along Aviara Parkway combined with site topography negated the need
for mitigation along this roadway.
In addition, second floor receptor areas denoted with an (I) in Table 2 would
require an interior acoustical analysis to determine acceptable construction materials
and design measures to lower interior noise levels to 45 dBA CNEL per California CCR
Title 24 Noise Insulation Standards. Any lots 'sandwiched' between these lots (or having
a line-of-sight to the roadway) would also require interior noise control measures. Thus,
for completeness, the identified lots requiring interior mitigation would be: 2 through 8,
60, 61, affordable housing unit windows facing Poinsettia Lane, 203, 204, 213 through
220, and 225 through 235 inclusive.
The interior acoustical analysis should be completed prior to submission of final
architectural designs for the proposed units situated on the affected pads.
Aircraft Transportation Noise Sources Identified
The project site lies outside the influence areas of McClellan-Palomar Airport and
associated industrial uses. The airport is currently operating at full capacity (maximum
typical number of flight operations per day) and no appreciable increase in the contours
is expected within the project analysis horizon. Thus, no significant impacts to the project
site due to aircraft operations are expected.
Conclusions
Future noise levels for units located along Poinsettia Lane and Aviara Parkway
were found to be in excess the 60-dBA CNEL threshold established by the City. Exterior
and interior mitigation measures were deemed necessary to reduce impacts to below a
level of significance. The following mitigation measures are required:
1. Lots numbered 3 though 8, 60, 61, the affordable housing area, 203, 204, 213
through 219, and 231 though 236 were found to have projected future (ground
level) traffic-related noise levels in excess of the 60 dBA CNEL threshold
established by the City.
2. Noise mitigation would require noise walls ranging from five to seven feet to be
located along the rear property line between Poinsettia Lane and the residential
receptor. A schematic of the proposed wall design is shown in Figure 3.
Projected traffic volumes along Aviara Parkway combined with site topography
negated the need for mitigation along this roadway.
3. Due to its lack of exterior usable space, no exterior noise mitigation would be
required for the affordable housing area.
4. Second floor receptor areas denoted with an (I) in Table 2 would require an
interior acoustical analysis to determine acceptable construction materials and
design measures to lower interior noise levels to 45 dBA CNEL per California
CCR Title 24 Noise Insulation Standards. Any lots 'sandwiched' between these
lots (or having a line-of-sight to the roadway) would also require interior noise
Ms. Kathy Baker
Standard Pacific Poinsettia Property Acoustical Study
ISE Report #98-017
January 2, 2001 (Revised)
Page 9
control measures. Thus, for completeness, the identified lots requiring interior
mitigation would be: 2 through 8, 60, 61, affordable housing unit windows facing
Poinsettia Lane, 203, 204, 213 through 220, and 225 through 235 inclusive.
Should you have any questions regarding the above conclusions, please do not
hesitate to contact me at (619) 640-9379.
Sincerely,
Rick Tavares
Project Principal
Investigative Science and Engineering, Inc.
Cc: Emery McCaffery, ISE
Attachments: Figure 3 - Proposed Mitigation Design: Standard Pacific Poinsettia
Property Development
Figure 3: Proposed Mitigation Design (1/2/01)-Thompson Poinsettia Property