HomeMy WebLinkAboutCT 93-09; OCEAN BLUFF; ADDENDUM TO ACOUSTICAL STUDY; 1993-07-31,.,
James C. Berry -Acoustician
(619) 660--0064
Report No. 9321A
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 Al ..
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 FHW A 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
(619) 660--0064
CONCLUSION
Report No. 9321A
PageA2
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 311993
James C. Berry -Acoustician
(619). 660-0064
Elevat-Base of
Lot ion of Barrier
Road
92 339 339
91 341 341
87 345 350
86 346 ·350
84 353 353
83 354 354
82 356 356
Feet of
Observer
330
334
351
351
350
351
352
Table A 1 -Barrier Calculations
Source Barrier Distance Distance CNEL
Height Height Source to Barrier not
Autos Observer to attenua-
Med.trks Observer ted
Hvv.trks
0
2.3 0 245 5 63
8
0
2.3 0 205 5 64
8
0
2.3 7 140 5 66
8
0
2.3 7 110 5 67
8
0
2.8 6 60 5 72
0
2.3 6 60 5 72
8
0
2.3 5.5 60 5 72
8
Compo• FHWA
nentof Model
CNEL Attn.
Const.
62 1.37
53 1.33
54 1.24
63 .375
54 .353
55 .301
65 .200
56 .178
57 .126
66 .220
57 .190
58 .124
71 1.70
62 1.53
63 1.14
71 1.70
62 1.53
63 1.14
71 1.99
62 1.81
63 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
Report No.9321A
Table Al
Attenua-Attenua-
ted ted
Compo-CNEL
nent
50.6
41.7 52
42.9
54.4
45.5 56
46.8
57.4
48.6 59
50.0
58.3
49.5 59
51.0
58.9
50.3 60
52.1
58.9
50.3 60
52.1
58.4
49.7 60
51.5
James C. Berry -Acoustician
(619) .660-0064
Elevat-Base of
Lot ion of Barrier
Road
81 357 357
80 358 358
79 359 359
78 360 360
Barrier .doc
Feet of
Observer
353
354
354
354
Table At -continued
Source Barrier Distance Distance
Height Height Source to Barrier
Autos Observer to
Med.trks Observer
Hvv.trks
0
2.3 5.5 60 5
8
0
2.3 5.5 60 5
8
0
2.3 4.5 60 5
8
0
2.3 4.0 60 5
8
CNEL Compo-FHWA
not nent of Model
attenua-CNEL Attn.
ted Const.
71 1.99
72 62 1.81
63 1.38
71 1.99
72 62 1.81
63 1.38
71 1.91
72 62 1.73
63 1.31
71 2.21
72 62 2.01
63 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
Report No. 9321A
Table At (cont.)
Attenua-Attenua-
ted ted
Compo-CNEL
nent
58.4
49.7 60
51.5
58.4
49.7 60
51.5
58.6
49.9 60
51.7
58.1
49.4 59
51.2
. •
I
End of ----1-------------------50' o·-------------------
.__ __________ 30• o·-------------------20· o·------..i
Fence
Parkway Sidewalk Trail
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LEGEND
~ Recommended Open Space
•••• •••••• 110' S.lbaclc
t::I 2511. & Gr•ter Slapft
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~ Future Re¥eQetatlon ~
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DCS Disturbed Coastal SaQa Scrub
DRS Oisturoed Riparian Scrub
CLD Cout Uve Oak 'Noodand
Codi Summer Holly
Euc Eucalyptua
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Cagn Catitomia Gnatcatctw
Cofl Sand Aster
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Engalmann 0aJc. Watt-Slammed CNnotnua, Summar Holly• ~ Thtaated Wlliptail
Summer Holly 6 Walt-Shimmed CNnattlla
Summer Holly & EngalmMn Oak
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ltemative 'B I 'l •
Carlsbad Zone 20
Mitigation Map
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