HomeMy Public PortalAbout17 - 190522 RWDI Project 1902287- Arsenal Yards Building G - Air Quality Design Review 600 Southgate Drive Tel: +1.519.823.1311
Guelph,ON N1G 41D6 Fax: +1.519.823.1316
Canada www.rwdi.com .
MEMORANDUM
DATE: May 22,2019 RWDI REFERENCE#: 1902287
TO: Daniel Lucenti EMAIL: dlucenti@asR-architects.com
FROM: Mike Craig- RWDI EMAIL: Mike.Craie@rwdi.com
Aimee Smith - RWDI Aimee.Smith@rwdi.com
Kelly Baah- RWDI Kellv.Baah @rwdi.com
RE: Building Air Quality Design Review
Arsenal Yards-Building G
Watertown, MA
This memorandum outlines our early design feedback with respect to exhaust and air intake design for the
proposed Building G Laboratory at the Arsenal Yards Development in Watertown, Massachusetts.The purpose of
this early review is to identify any preliminary concerns with respect to air quality and exhaust re-entrainment
with suggestions for mitigation,and to identify the exhaust sources of most concern for further evaluation in the
detailed numerical dispersion modeling phase of our work to be completed in design development.
Our review is based on architectural and mechanical schematic design drawings,communication with the design
team,our recent visit to the site,and general knowledge of exhaust dispersion behavior and wind flow around
buildings.
PROJECT DESCRIPTION
The proposed laboratory building will be nine-stories tall, plus penthouse and will include primarily tenant
laboratory and office spaces. Building G will be located on the south side of Building F,which includes three
residential floors on top of a five-story parking structure. Building G includes a lower roof at level 3 adjacent to
the Building F parking structure with a grade-level breezeway below. Other immediate surrounding buildings will
include Building A to the west(a mixed-use building, serving laboratory/office and commercial tenants),and
Arsenal Park to the southwest. Additional developments planned for the Arsenal Yards site include new and
renovated residential, hotel,and commercial buildings to the north.A rendering of Building G along with existing
and proposed surrounding buildings is shown in Image 1.
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BUILDING AIR QUALITY DESIGN REVIEW ,
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
Building El Building G
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Image 1:Rendering of Building G and Adjacent Buildings
Proposed Exhaust and Air Intake Design
The proposed Building G mechanical design includes the following exhausts located at penthouse level (shown in
Image 2):
• Four(4)4,000 MBH natural gas fired boilers;
• Three(3)450 ton and one(1)350 ton cooling towers;
• One(1) 1,000 kW life safety diesel generator and one(1)750 kW natural gas standby generator;
• Two(2)115,000 cfm laboratory exhaust air handling unit systems(three fans each);and
• Eight(8)future tenant specialty exhausts(as needed).
The Building G loading dock will be located at the northeast corner of the building,which will be partially covered.
Air intakes serving Building G will be located on the east and west facades of the penthouse.
It is understood that there is a possibility of a future tenant vivarium fit-out that could include an exhaust
(approximately 10,000 cfm)and an air handling unit(AHU)as well as a standby generator. The design concept
would include routing vivarium exhaust to discharge from the upper roof of Building G,with the tenant AHU and
generator located on the level 3 roof adjacent to Building F(shown in Image 3).
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BUILDING AIR QUALITY DESIGN REVIEW
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
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Image 2:Proposed Building G Roof Plan Showing Exhaust and Intake Layout
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Image 3:Isometric View of Development Showing Building G Roof Plan Levels
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BUILDING AIR QUALITY DESIGN REVIEW ,
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
SITE CONDITIONS
Based on our understanding of the site and a review of drawings for the adjacent Buildings A and F,there are
exhausts on these buildings that may be of concern for air quality at the proposed Building G air intakes. Notable
exhausts of concern on these buildings are listed below and illustrated in Image 4.
• Building A
0 500 kW Emergency Generator Exhaust;
0 Three(3) 17,670 cfm and four(4) 13,250 cfm Manifolded Laboratory Exhausts;
0 2,500 gpm and 600 gpm cooling towers;
0 Natural Gas Fired Boilers
0 Possible Future Tenant Kitchen Exhausts
• Building F
0 250 kW Natural Gas Generator Exhaust
0 Two(2)Future Tenant Kitchen Exhausts
7
Laboratory and Emergency Horizontal Gas Fired Laboratory and Cooling Future Tenant Gas Fired
Diesel Generator Exhausts � Boiler Flues Tower Exhausts Kit€hen Exhausts Generator
Exhaust
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Image 4:Site Plan showing Proposed and Existing Exhaust Sources and Air Intakes
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BUILDING AIR QUALITY DESIGN REVIEW ,
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
Image 4 also illustrates the air intake locations(green)and pedestrian areas(yellow)that may be of concern with
respect to the proposed Building G exhausts. The residential floors on Building F also include operable windows
(not specifically shown).The wind rose shown in the Image 4 illustrates the wind climate for the site.
Predominant winds generally occur from the northwest and southwesterly directions.
PRELIMINARY DESIGN FEEDBACK
Building G Rooftop Exhausts
• Discharging the primary exhausts from the upper roof of the Building is positive for dispersion as the
exhaust will discharge well above nearby air intakes, pedestrian terraces and the adjacent Arsenal park.
• Exhaust from the proposed cooling towers and natural gas fired boilers is not expected to be concern for
air quality at nearby AHU intakes or pedestrian spaces.This assumes that the boilers will be equipped
with low NOx burners and the combustion exhaust discharges through vertical flues without fixed rain
caps.
• The large manifolded laboratory exhaust air handling units will help to dilute any fume hood exhaust
before being release to atmosphere. As a result,these exhausts are not expected to be a concern during
full flow operations(approximately 38,000 cfm per fan). Numerical dispersion modeling for these
exhausts will focus on determining the appropriate level of fan turndown while still meeting design
criteria.
• The proposed specialty exhausts may require stack heights above the top of the proposed screen wall
depending on the anticipated chemical use. Individual exhausts such as these typically do not perform
as well as manifolded systems with respect to dispersion, as they are low momentum with limited in-
system dilution. If stack heights above the screen wall are not desirable, mitigation options could include
manifolding'like'exhausts together to provide additional internal dilution and higher momentum. This
could be achieved by specifying induction fans with bypass air such that tenant exhausts can be added to
the system in the future. Other options could include relocating the tenant exhaust shaft to the south
edge of the roof to take advantage of additional separation distance from the Building G intakes and
residential terraces and windows.The specialty exhausts will be evaluated in detail in the numerical
modelling phase of our work.
• The current design includes a 1,000 kW life-safety emergency diesel generator and a 750 kW tenant
generator. The tenant generator will be natural gas, pending approval from the city. Locating the
generator exhausts at roof level,above nearby intakes and terraces is positive. The flues should
discharge vertically without fixed rain caps(a hinged cap is acceptable provided it opens under all
operating loads).
o Combustion Pollutants-With flues extending to a height flush with the top of the screen wall, it
is expected that health criteria will be met at the proposed Building G intakes as well as at the
nearby Building F terraces and windows. Should the tenant generator be specified as diesel, it is
also likely that health criteria would be met.
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BUILDING AIR QUALITY DESIGN REVIEW ,
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
o Diesel Odor-Given that diesel generator exhaust is very odorous,odors may reach the nearby
Building G intakes during southwesterly and southeasterly wind conditions when the diesel life-
safety generator is exercised. Odor is not a concern for natural gas engines.The frequency of
wind conditions resulting in odors will depend on the final flue placement and number of diesel
engines. Testing the generator during low building occupancy hours would help to reduce the
potential for odor complaints. Locating the diesel generator flue as far south on the roof as
possible would provide additional separation from the Building G intakes and take advantage of
the low frequency of southerly wind conditions at the site.
o Diesel odor is less likely to reach the Building F terraces and windows because the exhaust is
located well above these areas and wind conditions from the south,as seen in Image 4 are not
frequent for the site.
o The generator exhaust flue(s)will be evaluated in detail with numerical dispersion modeling
during design development to provide recommendations on stack height.
Possible Future Tenant Vivarium
• Routing the vivarium exhaust to discharge from the roof of the building(as opposed to the level 3 low
roof), is positive and highly recommended. It is likely that the exhaust would not need to extend above
the top of the screen wall provided that it is at least 30 ft from the nearest Building G air intake. This will
be confirmed in the numerical modeling assessment.
• Locating the emergency generator on the level 3 low roof will be problematic from both an air quality
and noise perspective. Given that there are terraces and windows in close proximity to the unit, it is
likely that elevated pollutant levels can reach these areas when the generator is exercised for many wind
conditions. This is a result of the of the exhaust being within the aerodynamic influence of the taller
buildings. Exhaust from the generator would also be a concern at the proposed vivarium AHU on the
Level 3 roof. Routing the generator exhaust flue to discharge from the roof of Building G would help to
disperse the exhaust above both the Building F terraces and windows and the vivarium AHU. However,
the engine remaining on the low roof would still be a concern for noise at the Building F terraces and
windows and a high-end acoustical enclosure and silencing will likely be required. RWDI will assess noise
issues further during design development. If possible,we recommend locating the future generator on
the Building G upper roof to address both air quality and noise concerns.
• Locating the vivarium tenant AHU on the low roof is acceptable provided that the combustion exhaust
from the vivarium tenant generator can discharge from the upper roof of Building G. Given that the unit
is in close proximity to Building F terraces and windows, noise is a potential concern. Locating the AHU in
the Building G penthouse and drawing air through the building intake louvers would help to reduce noise
impacts(locating the AHU on the upper roof could introduce additional air quality concerns). If the future
unit cannot be accommodated within the penthouse, mitigation measures such as intake silencing and
screening will likely be required for the Level 3 roof location.This will be further addressed in RWDI's
noise assessment during design development.
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BUILDING AIR QUALITY DESIGN REVIEW ,
ARSENAL YARDS-BUILDING G
RWDI#1902287 .
May 22,2019
Building G Air Intakes
• In general,the Building A exhausts are well separated from the proposed Building G intakes
(approximately 400 ft)on the west facade of the penthouse. Given this, exhausts on Building A are not
expected to present a significant concern for air quality at the proposed Building G air intake locations.
This assumes the future tenant kitchen exhausts are on the order of 5,000 cfm or less.
• It is understood that the Building F 250 kW emergency generator will be natural gas fired. This is positive
as newer natural gas fired generator engines are low emissions units and are generally not a concern for
odor. Given that the exhaust flue is well separated from Building G,the engine is not expected to be a
concern for air quality at the Building G intakes.
• The Building F design includes provisions for three future tenant kitchen cooking hood exhausts located
at roof level. It is understood that the need for these exhausts will be driven by tenant requirements. If
these exhausts are anticipated to serve larger hoods(greater than 2,000 cfm)for full restaurant kitchens,
odors could reach the Building G penthouse intakes and future tenant vivarium intake on the level 3 roof
for a wide range of wind conditions(winds from the northwest through northeast and southerly
directions). The frequency of potential odors reaching the intakes will depend on the cooking activities
and final grease exhaust parameters. We recommend including the tenant kitchen exhausts in the
detailed numerical modelling to determine the level of concern. If needed,design options such as
locating the intakes farther south on the penthouse fa4ade or providing allowances for the future
addition of activated carbon filters would help to reduce the potential for odor issues from these
exhausts. If possible,an alternate option could include specifying pollution control units(PCU)for future
restaurant tenants in Building F with odorous cooking activities. This would also address odors reaching
nearby terraces and windows on Building F.
CONCLUSIONS AND NEXT STEPS
We would like to discuss the preliminary recommendations herein with the team at your earliest convenience. In
the meantime, please contact us with any questions. Our next steps will be to conduct a more detailed numerical
dispersion assessment during design development with a focus on the following exhaust sources:
• Building G
o Life-safety and Tenant Emergency Generators;
o Tenant Specialty Exhausts;
o Tenant Vivarium Exhaust;
o Manifolded Laboratory Exhausts(to confirm turndown potential);
• Buildings A and F
o Future Tenant Kitchen Exhausts
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