Water Reuse Study at the University of California Santa
Cruz Campus
Author: Tracy A. Clinton, P.E. (Carollo Engineers)
US-CA-Santa Cruz
Project Background
In response to the master plan for higher education,
the president of University of California (UC) asked UC
campuses to consider enrollment growth. For UC
Santa Cruz (UCSC), this request corresponded to a 25
percent increase in student population. Already faced
with severe water supply shortages and limited to no
possibilities for increases, UCSC decided to increase
self-reliance and sustainability of campus water
resources, and define measures for utilization of
recycled water. These goals were to be achieved while
considering challenges such as seasonal population
fluctuations of the UCSC campus, city water supply
limitations, campus elevation gradients, and the future
challenge of UCSC population growth. Although
campus water demand was expected to grow from 200
million gallons per year (MGY) (760,000 MCM/yr) in
2009 to 400 MGY (1.5 MCM/yr) in 2020, the city of
Santa Cruz had previously reported that there was
little to no increase in water supply available to UCSC.
In response, the campus began addressing challenges
by developing a decision analysis framework to enable
the selection and ranking of a range of potential reuse
projects that could be implemented both immediately,
and in response to future potable water and/or energy
reduction requirements.
Capacity and Type of Reuse
Application
Approximately one-half of the allocation of total
campus water consumption included non-potable uses
(Table 1) that could be offset by using alternate
sources (Maddaus, 2007). In addition, roughly 97 MGY
(0.37 MCM/yr) could be offset with recycled water,
rainwater, graywater, and well water, which are
available in sufficient volumes (Table 2). Both the
demand and the alternate water supplies have
seasonal dependencies that must be considered. For
example, water use is highest when classes are in
session and lowest during summer and between
quarters. The reuse opportunities that UCSC
considered were ones that minimize energy
2012 Guidelines for Water Reuse
consumption, maximize sustainability, and where
seasonal and spatial dependence considering varying
campus elevations of sources and demands for nonpotable water are aligned.
Table 1 Summary of non-potable water demands
Volume
Required
Seasonal
Demand
(MGY)
Dependence
Dependent on student
Toilet Flushing
6.3
populations
1
Irrigation
29
Dependent on weather
Dependent on student
Cooling Towers
82
populations and
weather
1
Volume for irrigation by the top 10 users; submetered
irrigation demand on campus is 40 MGY
2
Includes volume required at new cooling tower location
Table 2 Summary of alternate water supplies available
for non-potable use
Volume
Required
Seasonal
Demand
(MGY)
Dependence
Rainwater
8.3
Dependent on weather
Dependent on student
Graywater
13.8
populations
Dependent on student
1
Recycled
157
populations
Not seasonally
Well
56.5
dependent
1
Represents entire campus wastewater flow
The lower area of campus, which includes
administration offices and faculty housing, has an
elevation of 426 feet and receives about 30 inches (76
cm) of rain annually. The upper area of campus, with
an elevation of 982 feet (300 m) and about 48 inches
(122 cm) of annual rainfall, includes residences and
academic buildings. The middle area of the campus is
open space and agricultural land. Peak rainfall occurs
in January with little to no rain in the summer months
of June through September. Rainwater is currently
collected and systematically conveyed from the
campus to minimize erosion. Figure 1 shows the
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Appendix D | U.S. Case Studies
existing
non-potable
supplies
and
demands
by
general
campus
location/elevation. Options for replacing
potable water demands were identified
and
grouped
with
respect
to
implementability into immediate, nearterm, or long-term projects.
Water Quality Standards and
Treatment Technology
The regulatory requirements defined for
reuse of non-potable sources are outlined
in Table 3.
Project Management Practices
A “Model College” was developed as a
planning tool. This model considers nonpotable supplies and demands assuming
100 beds (i.e., residential component
only). This model can be used by the
campus to analyze future proposed reuse
projects regarding demands relative to
non-potable water supplies, sustainability,
and energy use. UCSC now has tools to
move aggressively to offset the increased
water demand that will accompany its
growth. The campus potentially has more
supply of non-potable water than demand
for it, so factors other than maximizing
supply can be figured into project
selection. For example, future project
selection criteria include cost per gallon of
non-potable water, construction cost of
specific projects, volume of potable water
offset, components of sustainability
(mainly
environmental
impacts),
educational value, and ease of operations
of the project.
Figure 1
Existing non-potable supplies and demands on UC campus
The cost of implementing a reuse project is largely
driven by the storage volume required for it, thus
matching the seasonality of supply and demand (such
as using rainwater for toilet flushing instead of
irrigation) helps in reducing the cost of reuse projects.
Another driver of cost is the proximity of supplies and
demands because of energy requirements for
pumping, particularly on this campus, which has over
550 ft (168 m) elevation difference between the upper
and lower campus areas.
2012 Guidelines for Water Reuse
Institutional/Cultural Considerations
The UC released a Policy on Sustainable Practices in
May 2007 which provided guidelines to all the UC
campuses to: Incorporate the principles of energy
efficiency and sustainability in all capital projects,
renovation projects, operations and maintenance
within budgetary constraints and programmatic
requirements. The current version of the Policy
TM
Silver certification for new UC
requires LEED
construction and existing renovations.
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Appendix D | U.S. Case Studies
Table 3 Requirements for reuse depending on source water
Appendix G
Graywater
Guidelines
Source
Campus
Title 22 Reuse Plumbing Codes
Guidelines
and Ordinances
Possible Reuse Applications
Irrigation, Toilet Flushing, HVAC
Rainwater
X
processes
1
Graywater
Subsurface Irrigation
X
X
Irrigation, Toilet Flushing, HVAC
Additionally Treated
X
X
2
processes
Graywater
Irrigation, Toilet Flushing, HVAC
Tertiary Treated/Disinfected
X
X
3
processes
Wastewater
Irrigation, Toilet Flushing, HVAC
Well Water
X
processes
1
Treated and applied as outlined in the California Greywater Reuse Guidelines - Appendix G, Title 24, Part 5, California
Administrative Code.
2
Treated to greater levels than outlined in the California Greywater Reuse Guidelines
3
Treated to levels outlined in the Recycled Water Requirements – Title 22.
A campus workshop was held to determine screening
criteria for construction and renovations; these criteria
were then used to review the proposed projects. Key
conclusions from the workshop included establishing a
minimum microbial water quality requirement for all
non-potable water, comparing the cost per gallon of
non-potable to potable sources, developing a “model
college” as a planning tool for future projects, and
considering the educational value of a project in the
project screening.
Successes and Lessons Learned
The campus study did not recommend which projects
should be implemented; rather it provided a decision
analysis framework to select and rank projects as
triggers occur that require a reduction in use of potable
water and/or energy. Project selection is a two-stage
process. First, the projects are grouped into
“implement,” “maybe implement,” and “currently
infeasible.” “Implement” reuse projects are those that
are the easiest to execute and that UCSC sees a clear
value in implementing right away. The “maybe
implement” are projects that merit further discussion.
The projects should also be sorted into immediate,
near and long-term periods. The second stage
involves screening and ranking the projects, such as
with a pairwise analysis, based on the screening
criteria developed at the beginning of the process.
A small subset of possible projects were selected
using the Campus Model based on input from USCS
staff; six near-term projects were identified (Table 4).
A trigger-based approach allows UCSC to implement
projects activated by flow triggers based on a demand
2012 Guidelines for Water Reuse
matrix. This approach considers meeting immediate
needs such as droughts, short-term needs when a
dormitory is being updated and refurbished, and longterm needs for future planned facilities. The outcome
of this project is being monitored by all UC campuses
for sustainably meeting growth demands. With the
implementation of projects identified on the campus,
UCSC has the opportunity to become a model campus
for schools and areas in water stressed regions
throughout the country.
Table 4 Summary of campus reuse projects selected
for near-term implementation
Project
Supply
Demand
1. East Parking Lot East
Field Irrigation
Rainwater
Irrigation
2. Porter College Toilet
Flushing
Rainwater
Toilet
Flushing
3. Biomedical Sciences
Facility Toilet Flushing
Rainwater
Toilet
Flushing
4. Jordan Gulch Middle
Fork Cooling Towers
Rainwater
Cooling
Towers
5. Irrigation
Recycled
Water
Irrigation
6. Family Student Housing
Landscape Irrigation
Graywater
Irrigation
References
Maddaus Water Management and UC Santa Cruz. 2007. UC
Santa Cruz Water Efficiency Survey, Draft Report.
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