DIR-2002-26b
CITY OF CUPERTINO
10300 Torre Avenue, Cupertino, California 95014 (408) 777-3308
To: Mayor and City Council members
Chairman and Planning Commissioners
C21
From: Steve Piasecki, Director of Community Development c'~
Date: August 22, 2002
Subject: Director's Minor Modification to 07-U-99 to install a roof top sound wall for the
HV AC equipment for the YMCA at 20803 Alves Drive.
Chapter 19.132 of the Cupertino Municipal Code allows for administrative
approval of minor changes in a project. The Director reports his decision to
the City Council and Planning Commission in time to allow an appeal of the
decision within fourteen calendar days.
DISCUSSION
The YMCA of Santa Clara Valley requests approval to install a roof top sound wall to
soundproof their HV AC equipment at their facility located at 20803 Alves Drive. The
3-foot high wall is proposed to be located on the east and south walls of the equipment
building adjacent to the swimming pool facility.
The YMCA received approval on August 9, 1999 (Use Permit 07-U-99) to construct a 9831
sq.ft. addition of an indoor swimming pool and aerobic studio to their existing building
at 20803 Alves Drive. On August 29, 2001, the owner and tenants of the multi-family
residential building located at 10225-10227 Beardon Drive to the east of the YMCA site
filed a complaint to the City regarding the noise of the HV AC equipment and the pool
exhaust fans on the east wall of the swimming pooL Noise measurements at 10225-10227
Beardon Drive indicated that the maximum noise level at the east fence due to the HV AC
fans was 56 dBA, exceeding the City's maximum allowed leveL As per the Chapter 10.48
Noise Control of the Municipal Code, the maximum daytime noise level (7 AM-8PM) at
the property line cannot exceed 65dbA and the maximum nighttime level (8PM-7 AM)
cannot exceed 55 dbA.
An acoustic analysis by a consultant indicates that the construction of a 3-foot high sound
wall would reduce the noise level by 3-4dBA at the property line. The material for the
sound wall is consistent with the acoustic analysis. Additional recommendations for
reducing the noise level (relocation of the pool exhaust fans and reducing HV AC fan
speeds) have already been completed. The abovementioned mitigation measures will
bring the noise levels for the YMCA in compliance with the City's noise ordinance.
Adjacent neighbors will be notified of this approvaL
ACTION
The Director approves the proposed addition, based on the attached plan set with the
following conditions:
1. The sound wall shall be 3-feet high.
2. Exterior finish for the sound wall shall match the existing building.
3. Structural calculations shall be provided with building permit application.
Enclosures: Exhibit A - Plan Set
Exhibit B - Letters from Environmental Consulting Services dated January 21,
2002 and March 8, 2002
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Environmental Consulting Services
Phone: (408) 257-1045
20430H To,m Cenier Lane Cupet1ino C\ 95014
FAX: 408 2577235
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January 21, 2002
?v1r. Craig Cesco
Property Director
rvletropolitan Office
1922 The Alameda
San Jose, C A 95126
RE: ~oisc Mitigation of Swimming Pool Fan Equipment at Cupertino'l:'1v1CA
Dear Mr, Cesco,
In response to your request I have evaluated the noise levels produced by the rooftop HV AC fan and
the two exhaust fans al the Cupertino )1vlC., and proposl:d melhods to meet City requircrnenls, Noise
measurements wen: made under nonnal operating c(lnditions for each of lhe installations. This report.
describes the field measurements of the operalional noise levels, tbe relevant Cupertino noise ordinance
standards, as well as the proposed measures to reduct: noise levels. Tht: mitigation effort involved ECS in
consultation \\itll the mechanical engineering design firm for the new pool conslfUclion, .American Consulting
Engineers.
NOISE MEASUREMENTS
Noise rneasucements were made of both sets of equipment during the morning of October 29. 2001.
ilnd for the pool HV AC again on the evening on January 18,2002. MeasuremenLS were made with a Rion
Model NL-l1 Precision Sound Level Meter and "N-X-OIA Octave Band Filler, calibrated with a B &. K
Model 4230 Sound Level Calibrator. Measurements wc:re made at several key locations, including locations
representing the highest noise levels at the property lines closesllO neighboring residences. M.eamrements
were made in decibels with A-weighting (abbreviated dB A), which modify low frequencies and high
frequencies to match human hearing sensitivity. Most noise ordinance standards are specified in dB A.
including the City of Cupertino's.
k Pool HV AC Fan Noise
The swimming pool HV AC equipment is installed on me roof at the northeast comeroftl1e new ,
swimming pool building. The large centrifugal fan associated with this. installation is approximately g feet
above the roof and can be heard in the absence of ambient noise at tbe north and east property lines. The fan
is operated 24 hours a day, but the speed is reduced 50% during evening hours between 10 pm to 6 am.
There have been some complaints ahout fan noise fr<lm adjaccntresidential propenies. Equil'll1ent noise was
measured initially with the equipment at full opent;onal speed al the following locations:
t. On the roof adjacent to equipment - approximately 15 feel from fan, in exhaust
direction
2. Back (north) property line at ne.;:lTeSL fence - gO feet
~ Side (east) property line at nearest fence - 30 feet
Additional property line measurements were made on the rooftop HV AC during evening hours and low
speed operation. Exhibit 1 following shows the noise levels measured at the three locations.
Environmental Con$ulting Services
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Cupertino
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40829801-43
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Cupertino 'YMCA Swimming Pool Equipment ;":oist
Page 3
Land Use at Location of Max Noise Le"el Max Noise Level
Complainl Night - 8 pm to , am Day- 7 llm to 8 pm
ResidentiAl 50 dBA 60 dBA
Non-Residential 55 dBA 65 dBA
SecliQ1ljO.48.050: EriefDaytime Jncjden~. During the daytime period only, brief
noise incidents exceeding limits in ol1ter sections of this ordinance are allowed, provided
that the sum of the nois!: duration in minutes plus tlle excess noise level does not exceed
20 in a two-hour period. For example, the: following combinations would be allowable:
Noise Increment above Noise Duration In 2-
Normal Standard Hour Period
5dBA I 5 minutcs
to dDA 10 minutes
] 5 dBA 5 minutcs
19 dHA 1 minutes
DISCUSSION OF EQUIPMENT NOISE MEASUREMENTS
A. Pool HV AC Fan Noise
The noise levels for the rooftop HV AC fan are highest at the propc;:rty line fencl:' on tlll: east side, 56
dBA when Ihe fan is. operating at full speed. This leveI is in compliance with Cupertino da}1ime noise
standards, but is 6 dDA above the evening standard. At the back property line, the fun speed 48 dBA noise
level is in compliance with both da)1imc and niahuimc standards. The Mise levels at the north fence are
much lower due to significanUy larger distance and the facl that the fan faces the opposite direction. . Of
coune, when the fan is operating at low speed tile noise levels also comply with both standards, The fan
noise at this location is 100t in the local traffic ambient noi~e under many conditions of temperature, humidity
and wind.
B. Pool Exbaust Fan Noise
The pool exhaust fans are generally used for less than an hour to exhaust air when chemicals have been
added to the pool. Maxim noise levels at the east fence are 61 dBA. For continuous operation, this level
would be only slightly over the daytime noise limit. As .1ShorHenn operation, it would comply with the
ordinance in daytime operation for up to 19 minutes in any two-hour period. These fans are not run at nigbL,
However, the City has requested that the YMCA reduce the noise levels below the ordinance standard to '
satisfY neighborhood concerns.
The follo\\ing mitigation measures are recommended for the two t)pes of equipment.
RRCOMMENDED MITlGA nON MEASl.iRES
A. Pool Roonop JWAC Fan
The existing perimeter wa 11 around the HV AC rooftop equipment ba}' rises 5.5 to 6.5 feet above the
equipmentlloor, which is slopctlto drain rainwater. The lop orUle noisy centrifiJgal fan is at a height of
approximately 9 feet. A noise reduction of 2.3 dB at the property lines could be achieved by raising the
perimeter wall heigbt h)' 2 f~t. Raising the wall 3 feet could imprO'il: the noise level by 3-4 dB. The wall
extension could be constructed of a double layer of 5/8" wood (with cracks between boards oifsel between
Environmental Consulting Services
.
.
Cupertino
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Cupertino 'YMCA Swimming Pool Equipment Noise
P.:lgt:4
the two layers) or the wall could be extended using the &i1me stucco construction as is now in place. In either
case all cracks and openings bem'ean Well! elcmenls should be thorougW:y sealed with non-hardening cau.lking
or glue. These measures would insure that noise level sundards are met when operating at half ~peed_
To meet the ordinance limits during a few hours when the fan must operate at full speed between 8 pm
and 7 am, additional Tm:asUTCs would be required for the fan exhaust duct and the fan enclosure, such as
quieting Jouvers, redirecting the duct, and/or enclosure noise mitigation materials (see pool exhaust fan
mitigation measures below). However, a simpler method to comply would be to always reduce fan speed
during the nighttime period.
B. Pool Exhaust Fans
The fans are pn:sently allached Lo the outside of the building by a short duct, with a set of weather,
louvers and a partial hood on the outlet side. The h.fCA wishes to use only one exhaust fan in the future.
Hence, a modification to the outlet side duct for one oflhe exhaust fans is recommended, as follows:
· Attach to the existing exhaust fan installation a duct that runs vertically to the roof
and directs the exhaust air horizontally toward tht: west across the roof.
· Line the duct with a composite noise mitigation material, as follows: a thin ('1..")
polyurelhane foam layer against the metal duct, a thin 1/64" lead layer, another W'
layer of polyurethane foOlIn, and fmally a plastic surface layer to reduce air
resistance Within the duct. There are several sources of manufactured composite
products oflhis type, including Kinetics Noise Control Inc. (614-889..Q480), The
Soundcoat Company (516-242-2220), and E. N. Murray Co. (303.892-1106).
!fyou need further assistance on this project, please let me know.
Respectfully submiUed,
SLot.ntS~
H. Stanton Shelly
Acoustical Consultant
Board Certified Member (1982)
Institute of Noise Control Engineering
Environmental Consulting Services
.,
.,
.,
Cupertino
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Environmental Consulting Services
Phone: (408) 257~I045
20430H Town Center Lane Cupertino CA 95014
FAX: 408 2577235
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j\,'larch 8, 2002
:.\11'. Craig Cesco
Property Director
MetropoliL1n Office
1922 The Alameda
San Jose, CA 95126
RE: Noise Impact of!\1oving Pool Exhaust Fans at Cupertino Th1CA
Dear Craig,
In response to your recent request, 1 have evaluated the potential noise impact of moving the two pool
exhaust fans to the south side of the pool building from the east end of the building, where they are installed
at present. I have analyzed the proposed new location for the fans from the building sketches you faxed to
me, The proposed new fan locations are on the south side of the pool building, approximately 90 feet and
120 feet ii'om the east end, and about 6 feet above the roof. I am assuming that the same fans that I measured
previously are being reinstalled.
After modeling the noise transmission for the new fan locations, it is clear th.'tt there would be
significant noise reduction at the nearby residential property line relative to the present location. There are
three significant contributions to a lower noise level: an increase in distance to the sensitive property line, a
noise balTier at the edge of the flat roof, which obstmcts the direct transmission path, and finally, the fact tJlal
the direction of fan exhaust would not be toward the sensitive property line.
\-Vithout going into great detail about the analysis, there would be a noise reduction of 14-17 dB
relative to the present installation. The result would be a fan noise level, when both are running, of less than
45 dBA at the residential property line. TIlis noise level not only meets the Day1ime Cupet1ino Noise
Ordinance, but also would meet the Nighttime Noise Ordinance standard of 50 dBA, for the times that the
exhaust fans need to be tun outside of the normal daytime period.
If you need further clarification or assistance on this project, please let me know.
Respectfully submitted,
S-C-CW'V Shelly
H Stanton Shelly
Acoustical Consultant
Board Certified Member (1982)
lnstitute of Noise Control Engineering
Environmental Consulting Services
*
Cupertino
:UBMITTAl
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NORTHWEST YMCA
20803 ALVES DRIVE
CUPERTINO, CALIFORNIA
PLANCHECKSUBNUTTAL
RoofTop Sound Wall
Recommended Mitigation Measures
The existing perimeter wall around the HV AC rooftop equipment bay rises 6.5 feet above the equipment
floor, which is sloped to drain rain\Vater. The top ofllie ~-entrifuga1 HVAC fan is at a height ofapproximately
9 feet. A noise reduction of2-3 dB at the property lines could he achieved by raising the perimeter wall height
2 feet. Raising the wall 3 feet coul~ improve the noise level 3.4 dB. Noise levels and recommendations were
completed by Stan Shelly of Environmental Consulting Services.
Scope Of Work
~ 1. A 2 x 4 frame will be built of treated Douglas Fir Lumber. -:3 J Ff. II/fill .
2. All wood will be painted before the frame is assembled.
3. The concrete board will be paint before assembly to match the
exterior color of the building.
4. The frame will be assembled with the Y2 inch concrete board
attached to top portion of frame.
5. Frame will mounted to parapet wall, with the concrete board
resting on the to of the parapet wall.
6_ The sound Wall frame will be attached to the parapet wall by
Y1 inch toggle bolts.
SUBMITTAl
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Sheet Index
AU Site Plan
A1.5 Roof Plan
A4-1 Building & WaIl Sections
1\5-1 Exterior Elevations
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S-5 Sections and Details
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SWl Sound Wall Detail
SW2 Sound Wall Detail
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SEP 9 2002 OCt 9 2d02 '� �� ��
P(�STED ON — �'HI:OI_?GH.��
' � ' C;' � � � �� _>�';���'�� �'L�:i:�-tz1:CO[�t�ER City of Cupertino
� �����, i_�:'�vis, Co��NT� ct�LtzK 10300 Torre Avenue
1s i �• �����1GHI ���;yUTY Cupertino, CA 95014
Notice of Exemption
To: County Clerk ;� � � . �F
County of Santa Clara �� ' .. F_. -:-� :-
191 North First Street
San Jose, CA 95113 S E P 9 2002
� BRENDr� llAVIS, Cou�rty Clerk-Recorder
Project Title n�-����-�h Santa C;lar� County�
� n�� �.. , � i � C'}-�Ul �putY
By �
Project Location -(be specific): 7(1Rn3 Ahec T�ri �P
Project Location -(City):�"n� l'roject Location -(County) �anta C:lara
Description of Project n�rectCLS minpr m� �ificatinn nf �a ��n��it tQ�ngtri��t a rnnf tn�
S��nci wall
Name of Public Agency approving project: �.iT of C�TP ;n�
Name of Person or Agency carrying out pr�ject vMCA Of Santa [ l�ra Va jev
Exempt Status: (check one)
_ Ministerial (Sec. 21080(b)(1); 152ti8);
_ Declared Emergency (Sec. 21080(t�)(3); 15269(a));
_ Emergency Project (Sec. 21080(b)14); 15269(b)(c));
� Categorical Exemption. State type and section number: r'�.rss 3�Pct�on 1 S�Ql �a�=�
TntPrinr anr� RxtPrinr A ItPratinnc
_Statutory Exemption. State code number:
Reasons why project is exempt �iPrt invnivec thP � n�etn��tipn pf a� ft hiah �nnnri
�x,all nn an ex�' g �c r�.
Lead Agency
Contact Person: Area code/telephone number �4(1Rl 777-��77
A � � I �
Signature: _.1�� �S � ]�ate• A�ust?fi, ��Q� Title Seninr Planner
g/planning/erc/dir-2002-26