HomeMy WebLinkAboutCT 93-09; Ocean Bluff; Tentative Map (CT) (97)c
Report No. 9321
June 7 1993
JAMES C. BERRY - ACOUSTICIAN
2401 Trace Road
Spring Valley, CA 91978
(619) 660-0064
REPORT ON AN ACOUSTICAL STUDY
Ocean Bluff
On the Extension of Poinsettia Lane
at Black Rail Road
City of Carlsbad
Prepared for:
Ocean Bluff Partnership
4370 La Jolla Village Drive, Suite 120
San Diego, CA 92122-1233
by;
James C. Berry
Acoustician
•
f.\ir- ft p/>«:, .,< u b
c
James C. Berry - Acoustician Report No. 9321
(619) 660-0064 Page 1
REPORT ON AN ACOUSTICAL STUDY
Ocean Bluff
on the Extension of Poinsettia Lane
at Black Rail Road, Carlsbad
INTRODUCTION
Ocean Bluff will be a 97 lot residential development to be located on the north side of the
eastward extension of Poinsettia Lane, west of Black Rail Road (Thomas Brothers Map No.
19 E3.) Access to the site will be from Black Rail Road which will be a 60 foot collector
street. Poinsettia Lane will be a major arterial road with a 102 foot wide right-of-way and a
posted speed limit of 50 mph. There will be 16 lots whose back yards will face on to
Poinsettia Lane. A partial site plan is shown in the attached Figure 1.
EXISTING CONDITIONS
The site was visited on Wednesday, June 2 1993, for familiarization purposes and to make
noise measurements. Poinsettia Lane currently has its eastward termination at Alga Road,
which continues south and east to El Camino Real thus providing an east-west connector to
Interstate Highway 5. (The Poinsettia Lane extension will replace this connection.) At the
site there are no roads existing and the ground is virtually undisturbed. The existing noise
ambient is due only to distant traffic and aircraft overflights due to operations from the
McClellan Palomar Airport.
Access to the site was limited, but a single noise measurement location was chosen along the
future Poinsettia Lane alignment, as far from the existing termination as possible. There
was no direct line-of-sight to any noise source except for overhead aircraft.
The single 30 minute noise measurement was made using a Quest Electronics Precision
Integrating Sound Level Meter, Type 1800, Serial No. HP 0050017, incorporating a
Condenser Microphone Type MK 224, Serial No. 89335, with calibrations traceable to the
National Bureau of Standards dated September 25, 1992. The sound level meter meets all
applicable U.S. and International Standards for Type 1 instruments (ANSI S 1.4-1983; IEC
604-1979 and 804-1984.) The meter was calibrated prior to use with a Type CA-22 Pressure
Calibrator, Serial No. J0040042. It was then mounted on a tripod at a height of 4 feet from
the ground and fitted with a windscreen.
James C. Berry - Acoustician
(619) 660-0064
Report No. 9321
Page 2
The results of the noise measurements were as follows:
All Noise Levels in dB(A)
Highest
Recorded
Lmax
67
Lowest
Recorded
Lmin
34
Average Leq
47
Time of Day
10:14A
10:45A
Duration
Min.
31
The Lmax was caused by an aircraft overflight. The Lmin represents the underlying ambient
without any local noise sources. The 31 minute Leq can be taken as representing a typical
weekday, daytime hourly average [Leq (hour)]. The long term average community noise
equivalent level (CNEL) can be obtained from the expression
CNEL = Leq (hour) + 2 dB(A)
Thus at the measurement site the noise level was 49 dB(A) CNEL.
Although it has no bearing on the project, traffic was counted at the Poinsettia Lane/Alga
Road intersection while the noise measurement was under way. Poinsettia Lane is a four
lane divided highway, with a posted speed of 40 mph. A total of 186 vehicles was counted in
30 minutes, including 9 medium trucks and 1 heavy vehicle. This was equivalent to 6,414
average daily trips (ADT) and is a minor noise source.
It should also be noted that the site is within the 3 mile radius influence area of the
McClellan Palomar airport but noise from this source was not found to be significant.
FUTURE NOISE LEVELS WITHOUT THE PROJECT
It is assumed that, even without the Ocean Bluff project, Poinsettia Lane will be completed
as a 102 foot right-of-way major arterial road from its present eastern terminus to at least
El Camino Real The posted speed limit would be 50 mph and the ultimate traffic flow
would be 24,800 ADT (Source: Site Plan and Traffic Study provided by Hunsaker and
Associates San Diego Inc.)
Noise levels due to the extended Poinsettia Lane cannot be derived from extrapolated
existing conditions. Therefore the available data were fed into the traffic noise prediction
model developed by the U.S. Department of Transportation, Federal Highway
Administration (FHWA-RD-77-108) modified for the CALVANO emission levels.
Assumptions were made that the vehicle mix would contain 2 percent medium and 1 percent
heavy vehicles, typical of area roads. The observer was assumed to be standing at the edge
of the right-of-way and the ground from source to observer was assumed to be hard. The
results of the calculations are shown in Table 1.
James C. Berry - Acoustician
(619) 660-0064
Report No. 9321
Page3
After passing the observer at the edge of the right-of-way, the traffic noise would then travel
over undisturbed soft ground with a propagation constant of 4.5 dB per doubling of distance.
Thus from a level of 73 dB(A) CNEL at the edge of the right-of-way, the major noise
contours would occur as follows:
Noise Contour
dB(A) CNEL
70
65
60
Distance from Road
C.L - feet
81
174
375
These noise contours are shown in Figure 1. Note that the calculations assume flat, soft
ground and take no account of shielding provided by the natural topography.
PROJECT IMPACTS
Construction
Construction will create a significant, mostly unmitigable but temporary noise impact in the
surrounding area. Machines associated with grading, excavating, paving, hauling and
building construction will be present at the site at various times.
The City of Carlsbad Planning Department Administrative Policy No. 17 does not cover
construction noise per se. In various jurisdictions around the County, construction noise is
either exempt from exterior noise level limits or is allowed only during the hours of 7 a.m. to
7 p.m. Monday through Saturday, and prohibited at all other times including all public
holidays. An average noise level of 75 dB(A) at an adjacent property line for 8 hours in any
24 hour period is also a common restriction. Local enforcement can monitor the time
constraints. Modern construction equipment properly used and maintained will usually
comply with the noise level limits. At completion of the project, all construction noise will
cease.
The City of Carlsbad's policy on construction noise will have be to be observed on this
project.
Project Generated Traffic
The traffic study indicates that the project will generate 980 ADT. This will use Black Rail
Road and then join traffic on Poinsettia Lane. Within the project this is low volume, low
speed self-generated noise. A total of 980 ADT in itself is not recognized as a significant
noise source. The traffic study indicates about a 50/50 split on Poinsettia Lane. Thus 490
ADT will be part of the 24,800 ADT passing the site, representing 2 percent of the total.
The acoustical contribution would be less than 0.1 dB(A) CNEL, which is insignificant.
James C. Berry - Acoustician Report No. 9321
(619) 660-0064 Page 4
Project Generated Noise
This will be a typical residential development within an area similarly zoned. Noise
associated with suburban living will be present. There will be no new or unusual noise
sources introduced into the area.
IMPACTS ON THE PROJECT
Exteror Noise
As can be seen from the contours on Figure 1, there are 8 lots directly fronting Poinsettia
Lane where noise levels are 70 to 73 dB(A) CNEL within their property boundaries. 10 lots
will have noise levels above 65 dB(A) CNEL and 28 lots are within the theoretical 60 dB(A)
CNEL contour line. These findings take no account of mitigation provided by the natural
topography or site grading.
The Carlsbad Policy No. 17 requires that exterior noise be mitigated to 60 dB(A) CNEL at a
point 5 feet inside the proposed project's property line at 6 feet above finished grade level
and above the first floor level if usable exterior space is provided. This is discussed below.
Interior Noise
Dwelling interior noise obviously depends on the exterior noise, unmitigated or mitigated.
As the dwellings will be fronting on to the project's interior streets, they will be set back
from Poinsettia Lane.
Typical California construction methods comprising wood framing, exterior stucco, interior
drywall, cavity insulation and standard glazing will provide 15 to 20 dB(A) of noise
reduction if windows and/or doors are left partially open and 25 to 30 dB(A) if all openings
are closed. (Source: County of San Diego General Plan.)
Carlsbad Policy No. 17 requires that no interior CNEL shall exceed 45 dB(A) when openings
are closed. As shown above, the minimum attenuation provided by a closed-up house is 25
dB(A) and thus, in the worst case, the exterior noise level could be as high as 70 dB(A) and
still meet the 45 dB(A) interior requirement. Figure 1 shows that, at all residence locations,
exterior noise levels will be below 70 dB(A) CNEL and the Policy No. 17 will be satisfied.
MITIGATION
Mitigation will be required at 15 lots directly facing Poinsettia Lane. This will have to take
the form of a barrier along the property lines or the top of a graded bank, whichever is most
convenient. The barrier may take the form of a berm, a wall or a combination of both.
o
James C. Berry - Acoustician Report No. 9321
(619) 660-0064 Page 5
In order to comply with Carlsbad Policy No. 17, mitigation ranging from 1 to 13 dB(A) will be
required. Using the site plan showing road and lot elevations, the "barrier" portion of the
FHWA model was used to determine barrier heights and resultant attenuations and noise
levels. The lots affected have been arbitrarily identified as A through O on Figure 1. The
assumption was made that the observer was standing 5 feet behind the barrier/wall which is
at the top of the graded banking. Because of the location of the project property line and the
grading requirements this is at variance with the wording of Policy No. 17 but is the only
practical assumption in this case. Also, the Policy No. 17 requirement for a 6 foot high
observer is different from the FHWA standard of 5 feet. The model was adjusted
accordingly and results in higher barriers than are normally required. It was also assumed
that barrier heights might be limited to 8 feet due to considerations of aesthetics.
The results of the calculations are shown in Table 2. Note that at lots A through F, the
noise level limit can be met with a 6 foot high barrier. Between lots G and K, the barrier
needs to grow to a height of 8 feet. From lots L to O, the 60 dB(A) CNEL contour cannot be
met with an 8 foot high wall, exceeding the limit by up to 2 dB(A). The wall would need to
grow to 9.3 feet high in order to meet the requirements. The location of the barrier is shown
in Figure 1 and should extend around on to Black Rail Road as indicated.
There should be no balconies facing on to Poinsettia Lane unless they are fully enclosed and
glassed-in.
Mitigation applied to lots A through O plus the presence of the houses on the lots will shield
all other lots in the project and no other mitigation is required
SUMMARY OF FINDINGS
The site is presently undeveloped and experiences only the existing rural ambient of about
50 dB(A) CNEL. The site is within the sphere of influence of the McClellan Palomar airport
and the daytime ambient is primarily due to this source.
Without the project but with extension of Poinsettia Lane as a 102 foot right-of-way major
arterial road, the site will be impacted by the noise from a traffic flow of 24,800 ADT
travelling at 50 mph. At the edge of the right-of-way, the noise level will be 73 dB(A) CNEL
and the unmitigated 60 dB(A) CNEL contour will extend to 375 feet from the centerline of
the road.
Construction will cause a significant, mostly unmitigable, but temporary noise impact in the
area. Project generated noise and project generated traffic noise will be insignificant.
o
James C. Berry - Acoustician Report No. 9321
(619) 660-0064 Page 6
The back yards of residences adjacent to Poinsettia Lane will have noise levels in excess of
60 dB(A) CNEL and will therefore require mitigation in order to comply with Carlsbad's
Policy No. 17. Mitigation will take the form of a barrier along the lot boundaries, on top of
banking provided by the lot grading. The barrier will need to be 6 feet high at the west end
of the project, growing to 8 feet high at the east end (at Black Rail Road.) At the 5
easternmost lots, the noise levels will be 61 and 62 dB(A) CNEL even with the 8 foot barrier,
which may be an aesthetic limit. Strict compliance with the 60 dB(A) CNEL limit would
require the barrier to grow to 9.3 feet high along these 5 lots.
Mitigated noise levels at the residences will be 60 dB(A) CNEL or below and interior noise
levels will not exceed 45 dB(A) CNEL with standard construction. Residences and
mitigation along Poinsettia Lane will shield all other houses on the project. There should be
no balconies facing Poinsettia Lane unless they are fully enclosed.
James C. Berry
Acoustician
o
James C. Berry - Acoustician
(619) 660-0064
Report No. 9321
Table 1
TABLE 1 - Noise Levels Resulting From Automotive Traffic
Calculated Using FHWA Traffic Model RD-77-108
CALVANO Emission Levels
Project: Ocean Bluff
Road: Poinsettia Lane
Section: West of Black Rail Road
Year: Future
Traffic Mix - Percent
Vehicle Speeds - mph
Automobiles
97
50
Viewing Angles - Degrees
ADT 24,800
Medium Trucks
2
50
Left 90
Distance to Observer from Centerline of Traffic - feet
Heavy Trucks
1
50
Right 90
51
All Noise Levels in dB(A) CNEL/Ldn
Noise Levels at Observer
Hard Ground
Automobiles
72
Medium
Trucks
63
Heavy
Vehicles
64
Total
73
Noise Contours
Distance from Geometric Center of Traffic - feet
Noise Level
Distance - Soft Gound
80
0
75
0
70
81
65
174
60
375
A distance of 0 feet is less than 40 feet from the CL of the traffic
fhwamodl.doc
James C. Berry - Acoustician
(619) 660-0064
Report No. 9321
Table 2
Table 2 - Barrier Calculations
Source
Traffic
on
Poin-
settia
lane
Lot
A
B
C
D
E
F
G
H
Elevat-
ion of
Road
318
319
321
325
327
332
336
339
Base of
Barrier
322
326
330
334
336
349.5
349.5
349.5
Feet of
Observer
323
327
331
335
337
350.5
350.5
350.5
Source
Height
Autos
Med.trks
Hvy.trks
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
Barrier
Height
5.9
5.9
5.9
5.9
5.9
6.0
7.1
7.7
Distance
Source to
Observer
360
330
290
255
210
150
100
85
Distance
Barrier
to
Observer
5
5
5
5
5
5
5
5
CNEL
not
attenua-
ted
61
61
62
63
64
66
69
70
Compo-
nent of
CNEL
60
51
52
60
51
52
61
52
53
62
53
54
63
54
55
65
56
57
68
59
60
69
60
61
FHWA
Model
Attn.
Const.
.00015
0
0
.00098
.0004
0
.0026
.0014
.00006
.004
.002
.0002
.0067
.0042
.0005
.062
.051
.027
.444
.398
.292
.739
.668
.505
Attenua-
tion dB
2.0
0
0
3.0
2.5
0
3.7
3.2
1.8
4.0
3.5
2.1
4.5
4.1
2.6
6.3
6.1
5.6
8.8
8.7
8.1
9.8
9.6
9.1
Attenua-
ted
Compo-
nent
58.0
51.0
52.0
57.0
48.5
52.0
57.3
48.8
51.2
58.0
49.5
51.9
58.5
49.9
52.4
58.7
49.9
51.4
59.2
50.3
51.9
59.2
50.4
51.9
Attenua-
ted
CNEL
60
59
59
59
60
60
60
60
o
o
continued:
Barrier.doc
James C. Berry - Acoustician
(619) 660-0064
Report No.9321
Table 2 (cont)
Table 2 (continued) - Barrier Calculations
Source
Traffic
on
Poin-
settia
Lane
Lot
I
J
K
L
M
N
O
O
(re-
peated)
Elevat-
ion of
Road
340.5
341
342
343
344
345
345
Base of
Barrier
349
349
349
348.5
347.5
346.5
346
Feet of
Observer
350
350
350
349.5
348.5
347.5
347
Source
Height
Autos
Med.tr ks
Hvy.trks
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
Barrier
Height
7.8
7.8
8.0
8.0
8.0
8.0
8.0
9.3
Distance
Source to
Observer
80
75
70
65
60
58
56
Distance
Barrier
to
Observer
5
5
5
5
5
5
5
CNEL
not
attenua-
ted
70
70
71
71
72
72
72
Compo-
nent of
CNEL
69
60
61
69
60
61
70
61
62
70
61
62
71
62
63
71
62
63
71
62
63
FHWA
Model
Attn.
Const.
.762
.685
.508
.780
.697
.508
.896
.801
.583
.876
.774
.543
.827
.719
.478
.747
.639
.404
.737
.626
.386
1.58
1.42
1.03
Attenua-
tion dB
9.9
9.7
9.1
9.9
9.7
9.1
10.3
10.0
9.4
10.2
9.9
9.2
10.1
9.8
9.0
9.8
9.5
8.7
9.8
9.5
8.6
11.8
11.5
10.6
Attenua-
ted
Compo-
nent
59.1
50.3
51.9
59.1
50.3
51.9
59.7
51.0
52.6
59.8
51.1
52.8
60.1
52.2
54.0
61.2
52.5
54.3
61.2
52.5
54.4
59.2
50.5
52.4
Attenua-
ted
CNEL
60
60
61
61
62
62
62
60
O
O
Barrier.doc
No. 9321
James C. Berry
(619) 660-0064
../ I / /•/
NORTH
110GI
SC/^&INFEET
FIGURE 1 - Partial Site Plan showing future contours
and location of noise mitigating barrier