HomeMy WebLinkAboutCT 93-09; Ocean Bluff; Tentative Map (CT) (98)James C. Berry - Acoustician Report No. 9321A
(619) 660-0064 Page Al
ADDENDUM TO THE REPORT ON AN ACOUSTICAL STUDY
Ocean Bluff, Carlsbad
INTRODUCTION
Since the original report (No. 9321) was issued on June 7 1993, revised information has
become available which necessitates this addendum. Grading elevations along Poinsettia
Lane have been changed, some lots have been revised and lot numbers have been added.
A revised partial site plan is shown in Figure Al. Note that lots directly bordering
Poinsettia Lane are now numbered 78 through 84. The backyards of lots 86, 87 and 90
through 93 face on to the road but are not alongside it.
FUTURE NOISE LEVELS
Future noise levels along the edges of Poinsettia Lane are as shown in the original report.
The unmitigated noise contours are shown in Figure A1. .
MITIGATION
Revised road elevations were obtained from the applicant and his engineer. The intersection
point of Poinsettia Lane and Black Rail Road is now at 360 feet. There is a gradual slope
down towards the west, the elevation being given as 347.4 feet opposite the boundary of lots
86 and 87. The elevations supplied by the applicant are shown in Figure Al. These values
were used to prepare a road centerline profile extrapolated towards the west end of the
project. Road elevations opposite each lot were read from the profile and rounded off to the
nearest foot. Pad elevations were read from the site plan and were also rounded to the
nearest foot.
It was noted that the newly proposed gradings are much more favorable to the project than
the original plan. Mitigation will still be required in the form of a wall or berm or a
combination of the two along the property boundary (or on top of a bank where the grading
dictates.) The height of this barrier was calculated as before using the "barrier" portion of
the FHWA traffic noise model. The results of the calculations are shown in Table Al.
It can be seen that, because of the graded topography, lots 91 and 92 (and 93) require no
further mitigation. The worst situation occurs at lots 86 and 87 where a 7 foot high barrier
will be required on top of the bank. At lot 84, the barrier will need to be 6 feet high,
gradually reducing in height to 4 feet at the corner lot, No. 78. The wall should be wrapped
around the corner at this lot. The location of the barrier is shown in Figure Al.
James C. Berry - Acoustician Report No. 9821A
(619) 660-0064 Page A2
CONCLUSION
Mitigation in the form of a solid barrier ranging in height from 7 feet at lot 87 down to 4 feet
at lot 78 will reduce noise levels in the back yards of the residences to 60 dB(A) CNEL/Ldn or
below and this will comply with the City of Carlsbad regulations.
As before, there should be no balconies facing on to Poinsettia Lane unless they are fully
enclosed and glassed-in.
James C. Berry
Acoustician
July 31 1993
James C. Berry - Acoustician
(619) 660-0064
Report No.932lA
Table Al
Table Al - Barrier Calculations
Lot
92
91
87
86
84
83
82
Elevat-
ion of
Road
339
341
345
346
353
354
356
Base of
Barrier
339
341
350
350
353
354
356
Feet of
Observer
330
334
351
351
350
351
352
Source
Height
Autos
Med.trks
Hvy.tr ks
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
0
2.8
0
2.3
8
0
2.3
8
Barrier
Height
0
0
7
7
6
6
5.5
Distance
Source to
Observer
245
205
140
110
60
60
60
Distance
Barrier
to
Observer
5
5
5
5
5
5
5
CNEL
not
attenua-
ted
63
64
66
67
72
72
72
Compo-
nent of
CNEL
62
53
54
63
54
55
65
56
57
66
57
58
71
62
63
71
62
63
71
62
63
FHWA
Model
Attn.
Const.
1.37
1.33
1.24
.375
.353
.301
.200
.178
.126
.220
.190
.124
1.70
1.53
1.14
1.70
1.53
1.14
1.99
1.81
1.38
Attenua-
tion dB
11.4
11.3
11.1
8.6
8.5
8.2
7.6
7.4
7.0
7.7
7.5
7.0
12.1
11.7
10.9
12.1
11.7
10.9
12.6
12.3
11.5
Attenua-
ted
Compo-
nent
50.6
41.7
42.9
54.4
45.5
46.8
57.4
48.6
50.0
58.3
49.5
51.0
58.9
50.3
52.1
58.9
50.3
52.1
58.4
49.7
51.5
Attenua-
ted
CNEL
52
56
59
59
60
60
60
V
James C. Berry - Acoustician
(619)660-0064
Report No. 9321A
Table Al (cont.)
Table Al - continued
r.
Lot
81
80
79
78
Elevat-
ion of
Road
357
358
359
360
Base of
Barrier
357
358
359
360
Feet of
Observer
353
354
354
354
Source
Height
Autos
Med.trks
Hvy.trks
0
2.3
8
0
2.3
8
0
2.3
8
0
2.3
8
Barrier
Height
5.5
5.5
4.5
4.0
Distance
Source to
Observer
60
60
60
60
Distance
Barrier
to
Observer
5
5
5
5
CNEL
not
attenua-
ted
72
72
72
72
Compo-
nent of
CNEL
71
62
63
71
62
63
71
62
63
71
62
63
FHWA
Model
Attn.
Const.
1.99
1.81
1.38
1.99
1.81
1.38
1.91
1.73
1.31
2.21
2.01
1.55
Attenua-
tion dB
12.6
12.3
11.5
12.6
12.3
11.5
12.4
12.1
11.3
12.9
12.6
11.8
Attenua-
ted
Compo-
nent
58.4
49.7
51.5
58.4
49.7
51.5
58.6
49.9
51.7
58.1
49.4
51.2
Attenua-
ted
CNEL
60
60
60
59
Barrier.doc
End of 50' 0'-
Parkway Sidtwalk Trail
EXHIBITS"D«t«
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Alternative 'A
SDG&E Easement
(Part of Specific Plan Open Space)
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Mitigation Map
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planning, design & environmental studies
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