WE Credit 2: Innovative Wastewater Technologies
LEED-NC Credit: YES | UNSURE | NO
Credit Intent
Decrease potable water demand while reducing wastewater discharge and recharging
local aquifers. This will help Stanford meet its water reduction goals.
Feasibility
Again, this credit should be pursued. It is probably more likely that this credit can be
achieved through Option 1 (because detailed on-site wastewater treatment guidelines
have not yet been established), which requires that potable water used for sewage
conveyance be reduced by 50%. The preliminary thrust of this project seems to
encourage water-saving strategies that will help to achieve this credit.
Analysis
To achieve this credit, we must show how potable water used for sewage conveyance will
be reduced by at least 50% when compared to a baseline case. Several assumptions are
made in this process, because finalized plumbing plans have not been published.
From ARUP’s pre-SD plumbing narrative, we know the following:1
● Waterless urinals will be used in Men’s restrooms (see Figure 6 below)
● Dual flush toilets will be used in all Women’s restrooms -- allows user to
choose between low and regular flow.
● A non-potable system for water closest flushing is planned
Design Case Assumptions
● From SS Credit 4.2, we assume the GSB will have 1,400 Full Time Equivalent
(FTE) occupants -- the FTE must remain consistent for all LEED credits.
● Per LEED-NC guidelines, it is assumed that the GSB will house half males and
half females (700 each)
● In a typical day a male will use a urinal twice and the water closet once, while a
woman will use the water closet three times.
● Assume that water closets are low-flow (1.1 gallons per flush).
● Because graywater or stormwater amount used for sewage conveyance are not
known, in the design cases we assume the amount to be equal to the amount of
water closest sewage generation. This is a
strategy, as noted above, that is planned by
ARUP.
● Assume number yearly workdays to be 300
-- many GSB users will probably be around
on weekends.
Figure 6: Typical Waterless Urinal2
1
2
ARUP, Pre-SD Plumbing Narrative, 4/30/07
Oikos Green Building Source: Waterless Urinal, http://oikos.com/products/mechanical/waterless/
WE Credit 2: Innovative Wastewater Technologies
LEED-NC Credit: YES | UNSURE | NO
Design Case
Fixture Type
Daily Uses
Waterless Urinal (Male)
Waterless Urinal (Female)
Watercloset (Male)
Watercloset (Female)
Flowrate, gpf
2
0
1
3
Occupants
0
0
1.1
1.1
Sewage
Generation, gal
700
700
700
700
0
0
770
2310
Totally Daily Volume, gal
Annual Work Days
Annual Volume, gal
Rain/Graywater volume, gal
3080
300
924000
924000
TOTAL ANNUAL VOLUME
0
Baseline Case Assumptions
Same number of daily uses and occupants as design case assumed. Flow rates of water
closets increased to 1.6 gallons per flush, and urinal flow rates increased to 1.0 gallons
per flush. We also assume that no rain or graywater is used for sewage conveyance.
Baseline Case
Fixture Type
Daily Uses
Conventional Urinal (Male)
Conventional Urinal (Female)
Watercloset (Male)
Watercloset (Female)
Flowrate, gpf
2
0
1
3
700
700
700
700
Sewage
Generation, gal
1400
0
1120
3360
Totally Daily Volume, gal
Annual Work Days
Annual Volume, gal
Rain/Graywater volume, gal
5880
300
1764000
0
TOTAL ANNUAL VOLUME
1764000
1
1
1.6
1.6
Occupants
So we see that we definitely have reduced potable water used for sewage conveyance, in
this case by using no potable water at all. It should be noted that if the calculations for
the design case hold in the actual GSB (i.e., all waterless urinals, and no potable water
used in water closets), then an Innovation Credit would be earned.
Also, if we disregard the planned use rainwater or graywater for sewage conveyance, we
still achieve a 47% decrease in potable water use. With some additional adjustments (i.e.,
using even a minimal amount -- 28,000 gallons -- of graywater) this credit could still be
achieved. [(1-(924000/1764000))*100 = 47.6%]