so-for-humanity

These goals may prove difficult to achieve, however, since the current sound levels—between
65 and 75 dB-are normally considered unacceptable for an outdoor recreational environment
(U.S. Department of Housing and Urban Development. 1984). Noise pollution studies by the
U.S. Environmental Protection Agency show that in addition to creating a disagreeable

•
•
r
environment for recreation, sound at this level at constant exposure contributes to the onset of
hearing impairment (City of Berkeley, 1977).
The noise generated from the traffic on Interstate 80, the principal noise source, will not be
eliminated or de-intensified in the foreseeable future. Traffic volumes on 1-80 past the site
measured at 204,000 vehicles per day in 1986 ( City of Berkeley, 1986). In addition, studies by
the California Department of Transportation show that this volume will Increase to
unacceptable levels by the year 2010 (City of Berkeley. 1986). This traffic increase with its
even greater start-stop congestion will inevitably increase further the already high level of
noise that reaches Aquatic Park.
Factors that influence traffic noise Include the weather, traffic parameters such as
compostion—the proportion of automobiles to light or heavy trucks—speed and density, and
road parameters such as width, road surface and design (Bugliarello, 1976). In a congested
traffic situation, repeated acceleration leads to increased engine noise. On the other hand, in
free-flowing traffic, transmission and tire noise caused by the compression and
decompression of air between the tire treads and the road surface (Bugliarello, 1976) contribute
to the high sound levels.
Additionally, the right-hand lanes of northbound traffic are often occupied by heavy trucks,
defined by having more than 26,000 pounds vehicle weight and three or more axles
(Department of Housing and Urban Development. 1984). Heavy trucks contribute a
significantly higher level of noise than lighter vehicles; moreover, the exhaust system
(assumed to be located at eight feet above the pavement surface, but which frequently is even
higher). Is the major origin of noise In these vehicles. This results in a greater magnitude and
spatial extension of noise than from automobiles, where the exhaust system and other noise
sources are considered to originate from ground level (Department of Commerce, 1978). The
significance of this comes into play when determining the dimensions of the soundwall. Sound Barrier Design at Aquatic Park
The design and construction of an effective sound barrier results from the satisfaction of
several physical criteria which are listed by the U.S. Department of Commerce (1978). A
soundwall must block the line of sight between the noise source and the receiver; it should be
constructed of a material with a surface weight density greater than 4 pounds per square foot,
and the barrier should be as airtight as possible. A barrier at Aquatic Park should be as long228
as possible given the land constraints since the freeway is a line source of noise and sound will
travel around the edges of the barrier and into the park.
To achieve adequate noise reduction at Aquatic Park, a barrier would have to span the entire
3000-foot border between the park and the freeway and would have to be of a height that would,
unfortunately, block the view of the city of Berkeley, especially from the northbound lanes
between Ashby and University Avenues. The soundwall would not. however, have to loom
directly over the freeway lanes because a 30-foot safety zone between the edge of the roadway
and the barrier must be maintained In lieu of an additional safety barrier (Bowlby, 1980).
Options In wall material and design allow for the possibility of creating an aesthetically
pleasing and unobtrusive sound barrier.
The dimensions of the area are crucial for determining appropriate barrier design. The
dimensions fall Into two categories: road and freeway widths which limit the options In
barrier width, and the widths from east to west across Aquatic Park which are used to
calculate the effective barrier heights. The northbound and southbound lanes with the clear
space between them total 54 feet in width. A 30-foot wide clear space exists east of the
northbound road edge and west of the portion of Bolivar Drive that parallels 1-80 (Figure 2).
':
x:::>-;:•:•;••;-.; <:•':'•
a 1
Key:
a. 36 ft. clear z
b. 1-80 south, 2
c. 10 ft. clear zi
d. I-80 north, Z
3 c d
one
2 ft. clear zon
Dne
I ft. clear zon
e f g
e. 30 ft. clear zone
e f. Bolivar Drive, 20 ft.
g. 6 ft. clear zone
3
zone
Figure 2. Cross-Sectional View of 1-80 at Aquatic Park
Source. Aquatic Park Base Map 1970. Berkeley Public
Works Department
-Bolivar Drive along most of this stretch has a width of 20 feet. The distance between the west
edge of Bolivar Drive and the shoreline on the far side of the lake range from approximately
300 feet at Allston Way. 400 feet at Bancroft Way and Charming Way. to approximately 500 feet
at Carlton Street.
For a situation such as Aquatic Park's where the source and reception points are on
approximately level terrain, the most effective placement of the sound barrier is at a point
closer to the receiver than to the source. Since most of the area between these points In
Aquatic Park is covered by water and since a wall established along the east shore of the lake
would not be viable, a position along the west edge is the only option. Given the existing space
constraints, and the need to maintain a 30-foot clear zone for reasons of safety. Bolivar Drive
is the best choice for a barrier location. By utilizing the space occupied by Bolivar Drive, a
soundwall could be Installed that would still allow for pedestrian or bicycle through-traffic
along the park-facing side of the wall.
Barrier Designs and Sound Attenuation
The height of the soundwall greatly affects the amount of noise that the barrier will block.
At barrier heights (H) of 10 feet. 12 feet and 15 feet the results In dB attenuation were derived
using workcharts (Figures 3. 4 and 5) from the U.S. Department of Housing and Urban
229
n _ ~
H
h 1 c
1 D
0 = observer: 5.5 ft.
S = source: 8.0 ft
R'= distance from source to barrier: 84.0 ft.
h'=(derived)
H = wall height; @10.0 ft., 12.0 ft. and 15.0 ft.
D'= distance from wall to observer: @ 300.0 ft., 400.0 ft. and 500.0 ft.
R
Figure 3. Sketch Showing Dimensions for Barrier Height Calculations.230
Development (1984). For these calculations several known mputs were required. The height of
the source (S) was taken as eight feet above ground level (the accepted level for truck noise). The
height of the observer or receiver (O) was taken at 5.5 feet. The distance from the source to the
barrier (R') was taken as 84 feet—the distance from the southbound lane of 1-80 to the west edge
of Bolivar Drive. The distance between the barrier and the observer (D') was taken as 300 feet.
400 feet and 500 feet. Through the calculation steps of Figure 4. (R) and (D) were calculated
where (R+D) is the slant distance from the source to the observer. The amount by which the
barrier protrudes above the line-of-sight between source and receiver (h) is also calculated
(HUD. 1984). With the values for (h). (R) and (R/D) the graph of Figure 5 yields "barrier
Workchart5 en»tr**>umtoc
Noisa Barrier
TolWKlR.O.ndhlromat»B««oo. H- *- TZ H.J13JS_
Fa ox tnt fouour*- wowr+r. c - p
lalQutntxwsft/viniOTl): O-. J »? "—
*/! i
1
{S^tt
ISDUMI rrrTTTTT7T7T7TT7TTTTTm
1. BwmDon of b«m»f top nvnus »-"iioo c* tourcm (M ft ) -
(S 6 ] c:
[' 4 1
2. E>*v»:on of 00—*W mnua •wvauon of SOurc* [°S.S ) -
I* 8 ] IB I'"i.5 1
XmD0tiaM*omm9unwoata$anBBbuaN9t(ff •+D") [J38t ]
4. Mao dounca otw—n t»m*r arc to-.xzm (R"; I4 8<f 1
lUM2dMdtfbyto*3 [«•**.« i -S- [J 38f ] - [tfcsiki*)
B- Sounf» th* puanDty on Uya 5 (La••rmjUx^ « Dy R»«tf);
tfwtyl po»*ftv«
7.40%0fkn*6
[s-a.S.u>">)
[ M 1
X
X
•i.S-io^]
4j.i*Mi"*] B
[**f.l-<»o"s]
[7l.-7«lo-s]
1 Or* mrus hn« 7 [ « ] -
V .T«io"s ] - ['.999 ]
B.Ur» 5 Brmt hr* A(wfl E*r*9«M «hr# 2 • rwgaov*) [«-«,.S«io**] X I' e* ] - I'-.ss ]
10. Lm» 1 mmus hn« 9 [' * ] -
[• -ss ] = ['•4.SS ]
11. Lint 10om*sifne6 ['M.S5 ) X [• .993 ] « ["A.5*f ] • »
12. L»n« 5 me' l*r*e 10 I'-UJS'to*] X [" 4.SS ] = ["-.018 )
13. Lxte 4 c . e-: &» hnt £ [' Bt )
T
[•
: [»8*r.l )
[" e*+.o-i ] = •>'14. Lint 13pushn« 12 ["84-.1 ]
15. lm* 3 mmm lr>e 4 [33«t- ] -
[4 8* ] • 1,s*4ot» ]
16. Ur* 15 c**»d &y k* 8 I,53oo ] + [8 •999 ] - ['•Soo.-b ]
17. L*w 16m«iu»hr>ti: [M»00» ) -
V -T018 ] • [n3oo:M> ) - o
Rc_r*r of R ana D IDmmtm r—pr. ft r>on*
o*cm«cH«ca
Figure 4. Methodology Sample: Calculations for a 12-Foot High Wall at
Receiver Distance 300 Feet.
Source. U.S. Dept. of Housing and Urban DevelopmentI
potential performance" of dB attenuation minus an adjustment to attenuation for loss of
ground attenuation. This error is scaled using (D/R) and the equivalence chart at the bottom
of Figure 5.
Although a 12-foot-high barrier was proposed by the California Department of
Transportation, calculations done according to the HUD workcharts (Figures 3. 4 and 5) show
that a 15 foot barrier would result in significantly lower decibels (Figure 6)-- a consideration
Workchart 6
Noise Barrier
Figure 5. Noise Barrier Worksheet.
Source. U.S. Dept. of Housing and Urban Development
231232
that might be useful in anticipation of lnterstate-80's Impending traffic volumes. With a 15-
foot-high wall in place, sound levels would drop to more acceptable decibels. For example, at
300 feet from the barrier sound at 75 dB would be received at 68.25 dB and sound at 70 dB would
be received at 63.25 dB. In contrast, a 12-foot-hlgh wall would attenuate noise to respectively
70.35 dB and 65.35 dB.
The material of which the soundwall is to be composed is limited by several factors. The
site's proximity to the marine environment of San Francisco Bay precludes the use of metal or
wood since climatic effects would take their toll on the wall. The other major factor Is the
limited construction space. The 20 feet available from Bolivar Drive Is not ample room for a
purely vegetative cover as the sound attenuation capabilities of a vegetative belt are
approximately 3 dB of attenuation per 100 feet of vegetation (Harris. 1988).
One possibility in soundwall design does, however, incorporate vegetation in the overall
barrier presentation. To promote both aesthetics and sound retention, a 15-foot-high concrete
barrier complemented with hanging plants or with a layer of trees lining the freeway side could
Experimental Soundwall Heights
10-foot 12-foot 15-foot
receiver distance
from soundwall:
300 ft.:
@75dB
@70dB
(dBA=3.1)
71.9 dB
66.9 dB
(dBA=4.7)
70.3 dB
65.3 dB
(dBA=6.8)
68.2 dB
63.2 dB
400 ft.:
@75dB
@70dB
(dBA=2.6)
72.4 dB
67.4 dB
(dBA=2.4)
70.6 dB
65.6 dB
(dBA=6.4)
68.6 dB
63.6 dB
500 ft.:
(5)75 dB
@70dB
(dBA=1.6)
73.4 dB
68.4 dB
(dBA=3.2)
71.8 dB
66.8 dB
(dBA=5.0)
70.0 dB
65.0 dB
(dBA : dB Attenuation)
Figure 6. Sound Levels Received in dB for Varying Barrier Heights at
Source Transmittances of 70 dB and 75 dB.
n
~be installed (Figure 7). The vegetation would serve several purposes: It would help to scatter
some of the approaching freeway noise: it would provide a soothing scenery backdrop: and It
would make the concrete barrier less suscepUble to soot and exhaust and less accessible to
graffiti artists. With or without complementary vegetaUon. the concrete barrier surface Itself
could be colored and textured to blend In with or enhance the area's landscape (Bowlby, 1980).
233
£^^f*TT .psaipip
a. b.
Figure 7. a. Concrete Wall with Hanging Plants, b. Concrete Wall with Plant Layer in front
of Barrier.
One other possibility is the construction of an earth berm. Although the construction of an
earth berm generally requires much more space, with careful structural design and by
combining the right construction materials, one could design a berm that would commence
within the 30-foot clear-zone but would have a slope gentle enough so that automobile hazards
would be minimized. According to the Federal Highway Administration Highway Traffic
Noise Prediction Model, earth berms are more efficient in sound attenuation than normal wall
barriers by about 3dB due to the berm's absorbtion or edge effects (Hajek. 1982). The earth
berm between 1-80 and Aquatic Park could therefore be constructed at a lesser height~a 12 -
foot barrier rather than the 15-foot example for a solid wall barrier (Figurt. 3). Another option
in line with the earth berm would include a pedestrian/jogger path cut Into the side of the berm
facing Aquatic Park. Earth berms nevertheless do have their drawbacks: they require acUve
maintainance against the erosive effects of climate.234
a. /
13.6*/ 27.7"
lake
/ 12' I-80 north
10" 10' 15' ' 15'
Bolivar Drive 30-Foot Clear Zone
b- r-y/ 27.7'
lake I I-80 north
/ I
Figure 8. a. Earth Berm Barrier, b. Earth Berm Barrier with Pedestrian Path.
Conclusion and Recommendations
If Aquatic park is projected to become a neighborhood or citywide recreational area in the
near future, some form of sound barrier must be constructed between the park and 1-80 so that
the park can actually be perceived as user-amenable. I feel that the most practical option in
barrier structure and design would be a 15-foot high concrete wall with a lining of vegetation
in the form of either trees or hanging vines. Due to the constraint of limited space, several
barrier options must be ruled out. A purely vegetative belt would not be possible and an earth
berm might, unfortunately, prove too costly and difficult to maintain. Although an earth
berm would tend to blend in better with the environment, a concrete sound shield could be
colored and textured to melt in with, or even enhance, the surroundings.
The major complaint about a soundwall is that it would block the view of Berkeley from the
freeway. So why do I propose a 15-foot high wall rather than a 12-foot high one? A 12-foot
high wall would already unavoidably block the view from the northbound lanes. The extra
three feet of sound-barrier height would not change matters from this perspective yet it would
considerably reduce the noise level at Aquatic Park. Travelers on the southbound lanes have
r—
1the Berkeley waterfront and San Francisco Bay to gaze at during their commutes. Finally, as
1-80 traffic volumes will rise steadily In coming years, a wall would be a nice shield for users of
Aquatic Park against not only the noise, but also the pollution and the general ugliness of the
freeway.
References
Bowlby. William. 1980. Traffic noise barriers in the United States: Inter-noise 80. v.2. pp.575
578
Bugliarello. George. 1976. The Impact of Noise Pollution; New York, Pergamon Press. 461p.
Daviss. S.R., G.R. Latham, and M.F. Palmer. 1980. Mayfield Road experiment noise
attenuation barrier. Inter-noise 80; v.2. pp.603-606.
Feriln, C.L., 1983. History and development of Aquatic Park, In Berkeley Water. Issues and
Resources; D Sloan & S. Stine, eds.: U.C. Berkeley Environmental Science Senior
Seminar reports. Berkeley, CA, pp. 127-133.
Hajek, J.J., 1982. Are earth berms accousticaliy better than thin-wall barriers; Noise Control
Engineering Journal, v 19, no.2, pp.45-51.
Harris, R.A., 1986. Vegetative barriers; an alternative highway noise abatement measure;
Noise Control Engineering Journal, v.27, no.l. pp.73-78.
Hayek. S.I.. 1980. Efficiency of double walled noise barriers; Inter-noise 80, v.2. pp. 585-590.
Maekawa. Z.. 1986. Acoustic shielding: noise reduction by thin and wide barriers: Scope, no.
24 .pp. 33-54.
May. D.N..1980. Ontario's highway noise barrier research; Inter-noise 80, pp. 571-578.
Menge. C.W.. 1980. Highway noise: sloped barriers as an alternative to absorptive barriers;
Noise Control Engineering, v. 14, no.2, pp. 16-21.
Miller. R.K. and W.V. Montone, 1978. Handbook of Acoustical Enclosures and Barriers;
Atlanta, Fairmont Press. 250p.
City of Berkeley. 1977. Master Plan; Mayor's Office. 204p.
1986. Berkeley Waterfront Plan; Amendment to the City's Master Plan, 125 p.
, 1988. West Berkeley Area Plan Phase III Report Unpublished report for the
City of Berkeley. Mayor's Office. 24p.
1988. West Berkeley Area Plan Working Report. Unpublished report for the
City of Berkeley. Mayor's Office. 32p.
U.S. Department of Commerce. 1978. Design Guide-for Reducing Transportation Noise in and
Around Buildings; National Bureau of Standards. Washington D.C.. 39p.
U.S. Department of Housing and Urban Development, 1984. Noise Assessment guidelines:
Washington D.C. 64p.
235