Texas; Rainwater Harvesting Systems For Residential And Commercial Systems

1. Rainwater Harvesting Systems for
Residential and Commercial
Systems:
Seaholm Power Plant and
Radiance Community
Community and Regional Planning Program
University of Texas School of Architecture
Austin, Texas

2. Urban Environmental Analysis
CRP 383: Fall 2005
Professor:
Kent Butler
Analysis Prepared and Presented By:
Jason Fryer
Additional Research:
Ahmed Abukhater
Ashley Francis
Kyle Irons
Andrew Judd
Wonsoo Lee
Nathan Meade
Vipin Nambiar
Mary-Elaine Sotos
Community and Regional Planning Program
University of Texas School of Architecture
Austin, Texas
July, 2006

3. Urban Environmental Analysis
CRP 383: Fall 2005
Acknowledgements
We would like to thank the following:
Seaholm Power Plant Development:
John Rosato
Southwest Strategies Group
Radiance Community Development:
Roger Kew
Radiance Water Supply Corp.
Proofreading:
Christa Arnold
Community and Regional Planning Program
University of Texas School of Architecture
Austin, Texas
July, 2006

4. Table of Contents
Integrated Water Resource Management
Integrated Water Resource Management 01
Rainwater Harvesting 05
Storm Water Management 10
Seaholm Power Plant
Seaholm Power Plant 13
Water Demand Modeling 16
Economic Analysis 21
Recommendations 25
Radiance Community
Radiance Community 27
Water Demand Modeling 31
Economic Analysis 36
Recommendations 43
Appendices
Ap pen di x A : S afe ty Co de s 44
Appendix B: Health C odes 51
Appendix C: Seaholm Site 53
Appendix D: Texas Water Related Data 55
Appendix E: Seaholm Demand Model 58
Appendix F: Stormwater Considerations at Seaholm 67
Appendix G: Radiance Scenarios 69
Appendix H: Radiance Modeling 74
Appendix I: Radiance Economic Analysis 80
Appendix J: Notes on Cost Analysis and Cisterns 85
Appendix K: Cost Analysis and Monthly Savings 87
Appendix L: Seaholm Cost Analysis 90

5. Integrated Water Resource Management
Background:
Integrated Water Resource Management (IWRM) has become a popular concept in
the practice of sustainable design and of resource management, and its sudden prominence
has led many to believe that IWRM is a new concept, created specifically to address current
water shortages. However, the true origins of IWRM can actually be found hundreds,
perhaps even thousands, of years ago. Evidence exists that both the Romans and the
Egyptians may have practiced Integrated Water Resource Management well before the birth
of Christ, but even discounting the contributions of these two remarkable civilizations,
tangible evidence is still available dating as far back as the tenth century. In Valencia, Spain,
the government was already forming participatory water tribunals to address the four major
components of Integrated Water Resource Management (Rahaman & Varis, 2005). While
the Spanish, in 1926, were perhaps the first officially to adapt IRWM as an organizational
model for water management (Embid, 2003), water resource management was adapted still in
the United States by the Tennessee Valley Authority as early as the 1940’s (Tortajada 2004).
In more recent years, Integrated Resource Water Management has been applied or has been
recommended in many cases and numerous examples of these programs began to develop
globally in the 1970’s and ‘80’s. However, despite its newfound prevalence, Integrated
Resource Water Management did not intrude upon the public awareness until the last ten
years as water management and water cost issues have become increasingly pressing and the
call for Integrated Resource Water Management was finally added to the agenda of several
world wide environmental conferences.
Definition:
In 2002, the Technical Advisory Committee of the Global Water Partnership offered
to Johannesburg World Summit the following definition of Integrated Water Resource
Management:
1

6. [Integrated Water Resource Management is] a process, which promotes
the coordinated development and management of water, land and related
resources in order to maximize the resultant economic and social welfare
in an equitable manner without compromising the sustainability of vital
systems.
Rahaman & Varis, 2005
This definition was used to set forth the basic goals of Integrated Resource Water
Management, and at the Johannesburg World Conference it was further suggested that these
principles should be applied within the bailiwick of good government and public
participation (Johannesburg, 2002). Unfortunately, despite all of the progress made by the
conference attendees, the final definition for Integrated Resource Water Management
manages to omit any concrete instructions for the technical aspects of IRWM, proffering
lofty ideals without providing any practical insight into the application of or the development
of an integrated water system.
Technical Aspects:
Integrated Water Resource Management has been hailed as a panacea for all the
world’s water problems; it is effective not only against short-term water shortages and cost
increases but also against the impending water crises of the future. After the Johannesburg
World Conference ended, both public and private individuals struggled with the application
of definition provided by the Technical Advisory Committee into a practical model for water
conservation and usage. In their report on Integrated Water Management for the Central
Texas Hill Country, Kent Butler and Andrew Karnoven suggest using an integrated approach
for water management (2004). Broken down to its basic components, Butler and Karnoven’s
integrated approach consists of the following four concerns that have been further refined by
the Urban Analysis Seminar at the University of Texas:
1. Water Demand: By analyzing water demand data in an integrated management
system it becomes possible to influence the water system systemically. The water
system infrastructure can be customized to fit the actual usage, thus reducing wasted
2

7. resources, and, in turn, this demand data can be used to educate the consumer and
hopefully to promote water conservation. The interplay of these two variables,
system size and actual water consumption, can be eventually mediated to produce a
more efficient allocation of water resources.
2. Water Supply: Hand in hand with the emphasis on water demand comes a focus on
the water supply itself. As water demand can only be reduced to a certain level, it
becomes necessary to balance conservation efforts with an increase in the volume of
water available to meet these demands. Rainwater collection, desalination
procedures, or wind harvesting each offer viable alternatives to a traditional well or to
a municipal water system.
3. Water Reuse and Reclamation: The third aspect of this integrated approach lies in
the reclamation of water from wastewater and from sewage. By focusing on water
reclamation and on rehabilitation, additional sources of water are created and these
procedures further ease the burden placed on the current water supply.
4. Storm Water Management: The final piece of the integrated water systems puzzle
is critical concern in modern building situations involving the treatment and the
disposition of storm water runoff. Besides being an additional source of usable water,
storm water management is also important to prevent surface erosion and to maintain
a healthy environment capable of contributing to an Integrated Water Resource
Management System.
Justifications:
The ultimate goal of any Integrated Water resource Management is the effective and
the efficient use of an important and of an increasingly scarce natural resource: water. To
accomplish this all four issues referenced above must be considered as well as the following
questions suggested by Butler and Karnoven:
1. How much water is actually used onsite by the new development?
2. What are the options for water supply sources, and what are the
tradeoffs?
3

8. 3. How much sanitary wastewater and storm water runoff is
generated on the site, and what are their likely water quality
impacts under different control strategies?
4. Can the various water uses and supplies in a new development be
better integrated so as to create more efficient, less consumptive
water services?
5. What is the economic feasibility of each of the multiple scenarios
and their respective water services?
6. More specifically, how feasible are some of the newer practices,
such as rainwater harvesting, in terms of technical requirements
and user acceptance on a subdivision scale, or an urban
development?
Butler & Karnoven, 2004
The ultimate goal for devising an Integrated Resource Water Management program is to
reduce the impact from a given site on the water supply both upstream and downstream. By
carefully considering all six of the above questions, as well as the four components of the
water system listed previously, it should become possible to achieve at least some modicum
of success.
4

9. Rainwater Harvesting Systems
Background
Much like Integrated Water Resource Management, rainwater harvesting not only has
begun to enjoy a newfound popularity, but also is a relatively antiquated concept.
Archeologists have found physical evidence of rainwater storage cisterns in Israel dating as
far back as 2000 B.C., with written evidence suggesting that the concept of rainwater
collection and storage techniques existed in China circa 4000 B.C. (Texas Water
Development Board, 2005). In early
twentieth century Texas, rainwater
collection systems received extensive
usage until municipal water supplies
became financially feasible and
readily available, causing rainwater
systems to wane both in popularity
and in frequency (Krishna, 2003).
However, in the last several decades,
rainwater systems have resurged with
Figure 1. Chinese Cisterns for Rainwater Storage
increasing frequency, particularly in
the more arid regions of the southwestern United States, where water shortages are rampant
and municipal water costs are on the rise. Currently in the United States, approximately
100,000 residential rainwater systems have been implemented, including more than 400
professionally installed, full-scale water harvesting systems in Central Texas alone. This
number is constantly on the rise, especially in cities such as Austin, Texas, where the city has
espoused a commitment toward sustainability and toward green building, going so far as to
offer incentive programs that have been responsible for the creation of over 6,000 rainwater
barrels in the city alone (Water Development Board, 2005).
5

10. Components
Rainwater harvesting is based on a very simple concept: collecting falling rain and
storing it for later use. To that end, a rainwater system can be as simple as a barrel set out in
storm to collect water for
a small garden, or it can
be complex enough to
satisfy the water supply
for an entire building.
Despite the vast
differences in complexity
and design, most domestic
rainwater systems are
made up of six main
components (Water
Development Board,
Figure 2. Residential Rainwater System
2005):
1. Catchment system: Many common rainwater systems will use the building’s
existing rooftop as a surface to collect the rainwater, although many newer systems
will add a pole barn or rain barn as a structure that provides additional surface area to
maximize the volume of water harvested.
2. Gutters and downspouts: Most houses already have existing gutters; however, it is
often advisable to upgrade these existing gutters when adding a rainwater system.
When installing gutters for a rainwater system, care is essential to correctly size the
gutters to handle the flow of water from the roof, and if the system is designated for
potable water, the gutters should be inspected for lead seams that can contaminate the
water supply.
3. Leaf guards: Leaf guards take several different shapes from funnels to baskets and
can be made of a myriad of materials, from nylon to stainless steel. Regardless of the
specific form, every leaf guard has a similar function: keeping the system clean and
6

11. maintaining the flow of water from the catchment surface to the storage area. In
addition to a leaf guard, many systems also include a first-flush diverter. This system
allows the first fraction of a rainfall to wash the rooftop and helps to remove any
debris and any detritus present on the roof.
4. Storage tanks: Often referred to as cisterns, the storage tank is one of the central
aspects of any rainwater system. All the water collected from the rooftop is first
stored in the storage tanks before it is re-implemented for use. As storage tanks get
more expensive when their volume increases, the tank size is often the determining
and the limiting factor in the capacity of a rainwater system (Appendix J).
5. Delivery system: Once the water is collected in the storage tank, a system is needed
to transport the water from the tank to the tap or into the house. While a gravity fed
system would be ideal, it is often necessary to add a pressure tank or a pump to
increase the water pressure into the house. Water only gains approximately one psi of
pressure for every 2.3 feet of vertical drop and most municipal water systems supply
between 40 psi and 60 psi to their domestic users; most internal water systems are not
designed to operate below this level. Even typical irrigation systems will require
between 15 psi to 20 psi to function properly.
6. Filtration system: A filtration system is suggested for all rainwater systems, but it
should be mandatory if the system is deigned for potable water. Various systems can
be installed, utilizing mechanical, chemical or even ultraviolet systems, and a
professional should be consulted before installing any rainwater system that is
intended for potable use.
General Concerns:
In spite of the relative simplicity of implanting a rainwater system, several serious
concerns must still be addressed. Both the Texas Commission for Environmental Quality
and the Texas Department of Health supply guidelines and regulations concerning the use
and treatment of water garnered from a rainwater harvesting system. The largest issue
central to both of these sets of code involves the end use of the water supply: potable (fit for
human consumption) or non-potable (not fit for human consumption).
7

12. • Potable Water: Potable water sources are generally dealt with under TCEQ Title 30
Part 1 Chapter 290 Subchapter D (Appendix A). This code sets forth guidelines and
requirements for the treatment of potable water sources. The TCEQ also put forth
requirements for the physical design of the system, the most important of which is the
need to maintain a separation between municipal water systems and rainwater
systems. The need to prevent cross-contamination can be satisfied by the insertion of
an air gap between the two systems or the use of a back flow prevention system.
• Non-Potable Water: Non-Potable water supplies have fewer requirements on their
implementation, but general guidelines are supplied by the Texas Department of
Health and can be found in Sections 341.037, 341.038 and 341.039 of the Texas
Administrative Code. The majority of the issues involved deal with public safety and
the elimination of public nuisances, but these codes should be consulted when
installing any type of rainwater harvesting system (Appendix B).
The TCEQ also provides a list of guidelines for water safety and for quality, as well as a
definition of public versus private water systems. Many of these issues are only suggestions
until the water system reaches a certain size, but the specific guidelines can be found either
by contacting the TCEQ or by checking their comprehensive website.
Benefits:
The obvious benefit derived from the use of a rainwater system is of course the
availability of a low cost alternative to the municipal water supply. However, the cost issue
only begins to scratch the surface when exploring reasons for the use of a rainwater system.
Due to rainwater’s nearly neutral pH and its general lack of impurities it is superior to ground
water or even to municipal water supplies for a host of reasons (Krishna, 2003):
1. Taste and Purity: Users of potable rainwater systems enjoy a higher purity of water
and, consequently, a better tasting supply.
8

13. 2. Soft Water: Rainwater is naturally a soft water and the lack of minerals eliminates
the need for a water softener. Additionally, the mineral deficit causes less wear on
appliances and on fixtures, lowering maintenance costs.
3. Contaminant Free: In addition to being naturally sodium free, thereby satisfying an
increasingly important dietary requirement, rainwater is free of many of the chemicals
that are added to municipal water supplies.
4. Natural Quality: Stored rainwater has been shown to be especially effective for
irrigation purposes; plants tend to thrive more from this source than from municipal
or from treated water.
Despite the obvious advantages, rainwater systems are not always viewed as economically
feasible. However, in addition to the purity issues qualified above, rainwater systems also
allow users to reduce the burden on the water supply during peak demand as well as
providing an alternative means to manage storm water runoff. The argument against
rainwater systems is that it is not fiscally viable when municipal water sources are present
(Peterson, 2005), but this counterpoint is only true in the narrowest view of the benefits of
rainwater systems. Balancing the palpable costs of installing a rainwater system against all
of the intangible benefits it provides is a difficult task; it becomes problematic to place a
strict monetary value on the importance of purity and of taste, or on the ability to reduce the
ravages of storm water runoff. However, this difficulty should not be allowed to discourage
the implementation of rainwater systems and in the future the advantages gained from their
use should far outweigh the systems’ monetary value.
9

14. Storm Water Management
Background
Under the traditional practice of storm water management, rainwater flows from yards
out into the street and into storm sewers. Impervious surfaces such as rooftops, driveways,
plazas, and streets do not allow rainwater to infiltrate into the soil. Consequently, water
flows quickly and in great volumes to streams and to lakes. Storm water carries sediments
and pollutants such as chemicals and fertilizers to creeks and rivers, causing the
contamination of potential drinking water and impacting the food chain that supports the
indigenous fish population. By keeping as much rainwater as possible in to proximity to
where it falls and by collecting and reusing this water, we can reduce adverse impacts on our
lakes and streams.
In the past, the primary concern centered on the removal of storm water runoff as quickly
as possible from the developed areas to achieve a convenient and a protected environment.
Channeling runoff with storm sewers, swales, gutters, and channels to the nearest water body
was, historically, the first line of defense. A more recent philosophy of storm water
management is to address on-site runoff by developing a comprehensive, integrated
approach, which contends with not only water quality but also to volume and to the rate of
runoff. Consequently, hydrologic problems can be minimized by preserving and by
maintaining the predevelopment drainage patterns to the greatest extent possible.
Further Studies Needed
It is necessary to explore the technical aspects of storm water for both of the projects in
greater detail. This includes understanding of the existing hydrologic characteristics as well
as engineering for the proposed system, which will establish size, storage capacity, discharge,
and infiltration rates. Further studies are needed to discern the amount of water generated
from the site and therefore the corresponding size of the storage tanks required to
10

15. accommodate the excess water runoff. Technical studies must be conducted to evaluate the
adequacy and the capacity of the infrastructure in both projects.
11

16. Seaholm Power Plant:
Study on the Feasibility of Installing a Rainwater
Harvesting System for Irrigation
Community and Regional Planning Program
University of Texas School of Architecture
Austin, Texas
December, 2005

17. Seaholm Power Plant
Built between 1950 and 1958, the Seaholm Power plant sits adjacent to Austin’s
Town Lake. During its lifetime, it housed five gas turbines and was capable of producing
approximately 100 megawatts of power. By the 1980s, the plant had ceased to produce
energy and was saved only in 1984 when a Historic Resources survey designated the
Seaholm Plant as a high priority historic building. Shortly thereafter, the City of Austin’s
Town Lake Comprehensive Plan “suggested that the plant be ‘converted into an activity
center complimentary to the area’ (City of Austin, 2000).” Thirteen years later the
Regional/Urban Design Assistance Team agreed with this recommendation and the
Seaholm Power Plant Reuse program was born.
The Seaholm Power Plant is located on West Cesar Chavez, in Austin, Texas.
The power plant sits on an eight-acre site on the north side of Town Lake, facing the
water. The site has been reconditioned
and following extensive clean up
operations, has been certified as safe for
human inhabitation and as
environmentally sound (Novak, 2006).
The five large gas turbines have been
removed from the interior of the
building, but much of the original
structure is still in place. The remaining
building consists of two subterranean
floors and a main floor with sixty-five
foot ceilings. The overall structure
measures approximately 110 feet by 235
feet and encompasses more than 100,000
square feet (Backus, 2005). Despite the
industrial nature of the structure, light Figure 1. Aerial View: Seaholm Power Plant
streams through two flanking rows of
13

18. clerestory lights near the ceiling to create an open, inviting, and naturally illuminated
space with potentially vibrant reuse.
Renovation Plans:
In April 2005, after the environmental cleanup and recovery of the Seaholm site
and approval of the EPA, the City of Austin selected the Seaholm Power, LLC
consortium to facilitate the renovations at the Seaholm Power Plant. Their mission
statement: to “build a dynamic urban center around Seaholm’s Power Plant as part of a
financially responsible public/ private partnership” (Landis, 2005). To this end, Seaholm,
LLC has suggested an environment open 24/7 to the public domain that will house Austin
City Limits and the new KLRU studio. The interior of the power plant will also host
commercial, retail and unprogrammed public spaces, while the exterior of the building
will feature a new multi-story office building and a ten-story residential tower (Appendix
C). In addition to these new residents, the site will also reflect the City of Austin’s
commitment to green building and to sustainability, represented primarily by a rainwater
collection and harvesting system that will optimize the extensive roof area covering the
existing buildings. Specific details of the proposed facility can be found in the Executive
Summary for the Seaholm Master Plan on the City of Austin’s website:
http://coapublish1.ci.austin.tx.us/.
Rainwater Supply
The rainfall data in the models is based on the median rainfall of the Austin, TX
region over the past seventy-five years. The median rainfall derived from this data was
24.17 inches per year. It is assumed that only 90% (ninety) of the total rainwater is
caught by the rainwater system. The rooftops evaluated in the models consist of the
existing Seaholm Powerplant (approximately 35,000 square feet), and the proposed office
building (approximately 30,500 square feet). It must be noted, however, that certain
schemes use these rooftops differently.
14

19. Rainwater Collection:
With approximately 65,000 square feet of rooftop surface available for collection
of rainwater, a rainwater system could be devised that would provide non-potable water
for use on site. This system would provide several different benefits not only for the
Seaholm Project, but also for the City of Austin itself. The rainwater collected from the
roof could be stored and then used to satisfy the irrigation requirements for the entire
development. Additionally, depending on the design of the rainwater harvesting system,
excess water could also be diverted to fountains and to other architectural elements, thus
severely reducing the load on the city municipal water system while also promoting
responsible water use throughout the remainder of the city. A secondary benefit derived
from the use of a rainwater system is the ability to control storm water runoff. The large
roof areas combined with extensive swaths of impervious ground cover create a site that
is extremely susceptible to the ravages of storm water runoff, and the site’s proximity to
Town Lake further increase the need to address critical storm water concerns (Appendix
F).
15

20. Water Demand Modeling
The purpose of modeling the water demands for a commercial rainwater
collection system was the analysis of various different combinations of rooftop collection
areas, rainwater storage needs, and water demands to find the optimal amount of
rainwater to be harvested to supplement the need for municipal water. The Seaholm
Power Plant development incorporates a mixture of uses, landscaping, and paving on the
existing site, Figure 2. The model intends to analyze the benefits of a hybrid system that
Figure 2. Seaholm Plant Proposed Development
16

21. meets its demands through different ratios of rainwater and of municipal water. In
addition to supplementing municipal water, the rainwater system also decreases the load
imposed on the municipal storm water system by capturing much of the rainwater that
would otherwise be directed into the surrounding storm water system. Most of the
scenarios evaluated are mixed systems; that is, those that use a combination of rainwater
and of municipal water to meet their demands for water. The models have been further
segregated into intended implementations of the collected rainwater as well as the ratios
of rainwater used versus municipal water used. Each of the scenarios was developed in
conjunction with an economic analysis to find the required system components and
eventually the cost of parts and the maintenance that would result from each.
A rainwater collection coefficient of 0.9 gallons of water per square foot of roof
area for every inch of rainfall was used for calculating the total rainwater that could be
collected. The coefficient ensures that the model incorporates concerns regarding losses
occurring from phenomena such as roof surface evaporation and associated with roof
washing, among others. The rainfall data used in the model is the regional median rainfall
rate beginning in 1930 and calculated monthly over a seventy-five year period (Appendix
D). The comprehensive nature of the data ensures that the model incorporates climatic
uncertainties that are typically tied to the effective functioning of a rain water system.
Each of the model’s scenarios was established with the intent of developing a hybrid
system to meet as much of the total demand as possible with rainwater without acquiring
large surplus or a deficit of water storage at the end of the year. Thus, the tanks were
sized in such a way that minimal water was spilled, and the ratio of demands met by
rainwater was determined by the comparison of the amount of rainwater collected and the
water demands of each month. Although the “end-of-month storage” fluctuated heavily
due to higher irrigation needs and lower rainwater collection amounts in the hot, arid
months, the system’s storage level at the end of the year was approximately even with
minimal net gain or loss.
The rooftops evaluated in the models consist of the existing Seaholm Power Plant
(approximately 35,000 square feet), and the proposed office building (approximately
17

22. 30,500 square feet), Figure 3. Each scenario uses the optimal combination of rooftop
collection areas needed to accrue the desired
amount of rainfall necessary to meet the typical
demand as determined by earlier analysis.
There is existing water storage, approximately
57,000 gallons, located in the power plant just
south of the Seaholm Power Plant, Figure 4.
The models revealed that this storage would
Figure 3. Rainwater Collection Areas
need to be supplemented, regardless of the
collected water’s expected use, therefore requiring additional rainwater storage tanks.
Each scenario requires differing quantities of additional storage ranging from 30,000
gallons to 100,000 gallons in order to produce an optimal system. The water demand
analyzed in the models is derived from multiple factors.
First, the outdoor water demands consist primarily of the irrigation of more than
65,000 square feet of landscaping, and filling decorative fountains that are approximately
12,800 square feet, Figure 4. It was assumed that the landscaping area consisted of three
major water categories of water demand: low, medium, and high water use. It was
assumed that 70% (seventy) of the
landscaping would be medium water use,
20% (twenty) would be high water use, and
10% (ten) would be low water use. Each of
these categories relates to the amount of
irrigation required in comparison to the
amount of water that is evaporated as a
result of climatic factors. The demand for
Figure 4. Rainwater Storage Locations
18

23. the fountains was based on a similar evaporation factor known as “pan evaporation rate”
(Appendix D). An additional evapotranspiration factor of 1.2 was used to account for the
additional loss of water as a result of spraying fountains, since the developers described
them as “decorative.” The greater surface area and the result of the wind on the spraying
water increases the amount of water lost above that of the pan evaporation rate. It also
was assumed that the fountain was filled with 25,000 gallons of municipal water prior to
running the system.
Second, the indoor water demands required consideration. In this development, it
was assumed that rainwater would only be used for non-potable (non-drinking) purposes,
such as the flushing of toilets in the Seaholm Power Plant building and in the proposed
office building. These values derived from a projected number of visitors and of
employees per day in each of the facilities. Using the International Building Code, the
quantities of occupants per square foot were
found based on the values given for the
usable square footages of the pertinent
buildings of the proposed development.
After finding the expected number of
occupants per day in addition to the typical
water demands of office employees and
retail visitors in the Austin area, the total
water demand for each month was Figure 5. Proposed Landscaping
calculated.
Analysis
The intent of this model is the exploration of the possibility of a rainwater
harvesting system to be incorporated into the proposed Seaholm Power Plant
redevelopment. It was an interest of the developer to explore the rainwater harvesting
system both for economic and for environmental reasons. The models aim to calculate
the amount of water demand that can be met with various combinations of rainwater
19

24. harvesting systems when applied to the proposed designs of the site. Therefore, to
examine the varying scales of rainwater collection systems possible for the Seaholm
Project, the model includes four design scenarios. While details of each scenario and
their subsequent evaluations can be found in Appendix E, the four scenarios can be
summarized by the following:
• Scenario A – Irrigation with 30,000 gallons added storage
• Scenario B – Irrigation with office bldg and 60,000 gallons added storage
• Scenario C – Irrigation and fountains with 100,000 gallons added storage
• Scenario D – Irrigation, fountains, toilets w/100,000 gallons added storage
Results
Each of the scenarios has unique advantages and disadvantages, but two in
particular appear most efficient. Scenarios B and C were able to implement effectively
the most amount of water in terms of what was collected. Although they both had
increased rainwater catchment areas from the proposed office building, they were also
able to use almost the entirety of what was collected due to the lower demands and
increased storage than in Scenario D. Scenario A showed that the Seaholm Power Plant
rooftop alone is insufficient to meet all of the landscape irrigation needs, but was able
still to fulfill over 50% (fifty) of them. The existing storage also was inadequate, since
the large roof area spilled a large volume of water during the months of heavy rainfall.
Scenario D appeared to be the most inefficient, because the addition of the indoor water
demands for toilet flushing was too great for the amount of rooftop collection per month.
It resulted in large deficits of rainwater use as well as resulting in a usage rate of only
36% (thirty-six), the lowest of the four scenarios.
20

25. Economic Analysis
The economic analysis model for the Seaholm project will compare the costs
associated with the four rainwater collection system scenarios to the cost of water
supplied by the city of Austin. Water price forecasting has indicated probable increases
in municipal water prices so the economic analysis model will include water price
inflation at 0% (zero), 1% (one), 2% (two), and 3% (three) percent, respectively, over
inflation itself, which is assumed to be 2% (two). Costs for the majority of the rainwater
collection system components in the Seaholm Project were obtained from the RS Means
2005 Building Construction Cost Data guidebook. It should be noted, though, that
because the Seaholm Project is a large-scale and complex development project, the costs
obtained for the economic analysis are very approximate and could be more or less,
depending upon project site issues and upon the final construction plans.
Similar to residential projects, the majority of the cost of a commercial rainwater
collection system is storage facilities (Appendix J). Additional storage volume clearly
can provide a greater volume of water available for use. Additional water supplied by the
system exponentially increases the benefit of the rainwater system. However, from an
economic perspective, storage should only be increased to a volume which can be
reliably filled and consumed by the collection and utilization system, otherwise the
potential benefit created through the cost of additional storage cannot be obtained.
For the Seaholm project, because of the high aesthetic priority, tanks placed above
ground are not an option. All of the scenarios include additional storage facilities and
only subterranean tanks will be considered in the analysis. Piping is required to connect
and to distribute water among the various collection, storage, and usage components.
Other required elements are pumping and filtration equipment. There are a large variety
of pumps that have the potential to be used in various design scenarios. The pumping
configuration will depend on specific storage elevation and site data and on irrigation
equipment pressure requirements. As a consideration towards implementation, system
maintenance costs were included in addition to the equipment replacement costs.
21

26. Although it is assumed building maintenance will have the capability to perform the
majority of maintenance tasks, an additional $50 monthly charge was included in the
system costs to account for minor system repairs, for adjustments, and for testing.
In the economic analysis, the cost of the rainwater system is measured the cost
avoided (through the collection of rainwater) of the volume of water which would have
been supplied by the water utility. Water is supplied to Seaholm from the Austin Water
Utility and the current 2005 rates are available on the City of Austin website:
www.ci.austin.tx.us/water/rateswr05.htm. For commercial customers such as Seaholm
water rates are $3.38 per 1000 gallons during the off peak season (November 1 through
June 30) and $3.62 per 1000 gallons during the peak season (July 1 through October 31).
For the purposes of this analysis, $3.50 per 1000 gallons will be used as the water cost
avoided through rainwater collection.
Creating the Financial Model for Economic Analysis
To analyze the economic aspects of the Seaholm rainwater collections system, a
financial model was created. The model was designed to allow the user the flexibility to
update inputs and to study the system costs as well as water savings implications over a
fifty-year time period. All replacement and maintenance costs are adjusted for inflation,
assuming an increase of 2% (two) annually. Water utility pricing was studied by
increasing increments of inflation above the model’s 2% (two) rate by 1% (one)
increments. The financial model considers four design scenarios and compares the
construction, the maintenance, and the replacement costs of those four options with the
cost savings generated from the water volume harvested (Appendix L).
Results
The accuracy of the economic analysis relies on the quality of the input data. For
the purposes of this study, the inputs have been fixed, based on information obtained
through research and through communication with various project representatives.
22

27. However, the value of the financial model is in the flexibility to refine inputs based on
more current research and on a more current understanding of the projects needs and of
its planned direction.
The Seaholm economic analysis looks at the relation of the estimated total future water
cost savings to the estimated total installation and maintenance costs of the rainwater
collection system on a yearly basis for each of the four design scenarios. The economic
model indicates that all rainwater system design scenarios under every water price
inflation factor have payback periods within the fifty-year analysis period. This result
suggests that from an economic perspective, almost any scale of rainwater harvesting
system at Seaholm will be a viable project. Table 1 summarizes the payback periods for
the four design scenarios.
As Figure 6 demonstrates, Scenario B has the shortest payback period, with a
scaled-down version of the system, represented by Scenario A, having slightly longer
payback periods. Scenarios C and D, which expand the rainwater collection to supply
other water uses like exterior
fountains and like indoor
Years to Achieve Return on Investment
Water Price Inflation (%) toilets, have longer payback
Scenario 2 3 4 5 periods due to the gratuitous
A 29 23 20 19
B 27 21 20 18 costs associated with the
C 34 29 26 22 additional storage and
D 46 36 30 27
conveyance equipment
Figure 6. Payback Periods required to configure the
rainwater system to serve those
purposes. This result suggests that financially, it is more beneficial to align the rainwater
collection system to serve as few purposes as completely as possible, than to partially
supply a larger, more diverse number of uses for the water. The payback periods for
Scenarios A and B also illustrate that as long as the water price inflation rate is a
minimum of one 1% (one) above normal inflation (represented by 3% (three) inflation),
the return on investment for the Seaholm rainwater harvesting system will take
23

28. approximately twenty years to achieve. The minimal one to two year decreases in
payback period shown with each 1% (one) increase in water price inflation rates indicate
that Scenarios A and B are less sensitive to water price inflation and that the return on
investment will most likely be achieved within a maximum thirty-year time frame under
any water pricing scenario that does not involve a decrease in the price of water. For the
Seaholm project, Scenario B would yield the greatest economic benefit by providing the
most rapid return on investment and because of the larger volume of water it supplies,
offering the greatest savings per year for the cost of the system above the savings which
could be attained under Scenario A.
24

29. Recommendations
Management Recommendations
The Texas Manual for Rainwater Harvesting recommends that county health
department staff and city building code staff be consulted concerning the construction of
the rainwater harvesting system and subsequent safe, sanitary operations. It is assumed
that the rainwater system installer will contact the necessary parties. To maintain safe
and sanitary operations, we recommend that the system and the landscape that it supports
be maintained by a dedicated landscape management company. It is not necessary that
they be on site full-time, however. Additionally, it is imperative that the company hired
be familiar with rainwater collection system, and it would be beneficial to have their
involvement from the inception so that they have a thorough understanding of the
components, the conveyance systems, and their integration in the landscape.
Monitoring Recommendations
The water collected at Seaholm will be non-potable but, because the water will
inevitably come into contact with humans, we recommend that the levels of certain
pathogens in the water be monitored regularly [The Texas Manual for Rainwater
Harvesting 2002]. Routine maintenance operations should be conducted to confirm that
the system is performing properly and efficiently. Additionally, disinfection systems
such as the automated chlorination system must undergo routine testing to ensure the
highest level of functionality.
25

30. Radiance Community:
Study on the Feasibility of Installing a Rainwater
Harvesting System as an Alternative Water Supply
Community and Regional Planning Program
University of Texas School of Architecture
Austin, Texas
December, 2005

31. Radiance Community
Located approximately thirty minutes west of downtown Austin, the Radiance
Community sits within a housing development in the Texas Hill Country. The
community itself is comprised of approximately forty lots and the developers and the
inhabitants share a common desire to tread lightly on their environment. With this goal
in mind, the Radiance Community contacted the University of Texas in hopes of
determining the feasibility of harvesting rainwater in an attempt to eliminate the need for
municipal water services.
Integrated Water Resource Management
To facilitate the process of completing a feasibility study for the Radiance
Community, the board members provided a
complete documentation of the water
demand for their community, as well as
detailed information on the water usage
patterns of the individual homes. This data
revealed that the Radiance Community’s
desire to adopt a rainwater harvesting
system was only a small piece of a larger
Integrated Water Resource Management
Figure 1. Typical Radiance Household
Plan. Analyzing the demand and the usage
data from the community, it is clear that many of the households within Radiance are
already involved in conservation efforts and in the regulation of water demand, the first
component of an IWRM. The desire for a rainwater system, coupled with the use of
community wells, clearly embodies the second tenet of an integrated system, while their
exploration of wastewater processing and of reclamation supports the third requirement
of water reclamation and reuse. The final piece of an integrated water program, storm
water management, while not specifically discussed, is nevertheless modulated by the use
27

32. of any rainwater harvesting system, creating a complete picture of Integrated Water
Resource Management.
Radiance Residential Development
With respect to the site design of the project, the main challenge is achieving
integration of specific management devices into the existing landscape. Many design
issues must be taken into account, some of which are safety, cost, maintenance, site
suitability, and appropriateness and multiple use. To reduce the risk of erosion, protection
is necessary at the outlet of all pips and paved channels where the flow velocity exceeds
the permissible velocity of the receiving channel or area. Structurally lined aprons or
other energy-dissipating devices are commonly used.
In addition, Best Management Practices (BMPs) can be adopted to reduce pollution,
to control runoff, and to integrate with the natural and the built landscape. Management
practices that include wet ponds, detention facilities, infiltration facilities, and waste
quality basins can be used singly or in a combinative effort. Devisers are channels that
direct excess water away from areas where it is unwanted and diverts it to areas where it
can be disposed appropriately. Reducing the impervious surface areas, especially parking
lots, can also reduce storm water runoff
quantities as well as minimizing
construction and maintenance costs. As
shown in Figure 2, the use of permeable
paving is a recommended alternative for
low-traffic parking areas, for emergency
access roads, and for driveways. The use of
natural landscape provides important
benefits for water quality and for the habitat
itself in addition to its lower costs for
installation and for maintenance than those
Figure 2. Permeable Pavement of conventional landscaping.
28

33. Radiance Project
A municipal water utility collects, treats, and distributes water to various facilities
with the equipment, the operation, and the maintenance costs incorporated into the fee
that the utility company charges the water users for their volume of water utilized. With
residential rainwater collection, the various components of the water supply system are
located on the property of the residence and they are owned, operated, and maintained by
the person who lives there. In the economic analysis we will be disregarding non-
monetary motivations for installing rainwater collection such as water resource
conservation and as environmental stewardship and focus solely on a cost comparison of
rainwater collection water supply systems and the foregone cost of drilling a new well.
The Radiance Water Supply
Corporation distributes water to
the majority of the thirty-six
residences in the Radiance
subdivision with a couple of
homes within the community
already using rainwater
collection as their water supply.
The water source utilized by the
Radiance Water Supply
Corporation is Edward’s Aquifer
that is pumped from a well
located on the Radiance property.
Cost considerations for this water
supply include the lifespan of the
well and of distribution facilities;
however, creating an accurate
Figure 3. Residential Rainwater Harvesting System
29

34. economic model for the municipal water supply is outside the scope of this analysis and
instead, the cost comparison will be based on the current price per gallon for well water.
A rainwater collection system is essentially made up of three main subsystems: a
capture subsystem, a storage subsystem, and a distribution subsystem (Figure 3). The
capture subsystem includes the roof, the gutters, and the roof washer/diverter; the storage
subsystem consists of the storage tank, and the distribution system includes a pump and
filtration and treatment equipment if the water is to be used for potable purposes. Piping,
typically PVC, is used to connect the three subsystems. A few of the system components,
such as the roof, the gutters, and the interior piping, are features of a residence that are
present whether there is a rainwater collection system or not, and therefore will not be
included in the economic analysis. Installation and maintenance costs, with the exception
of part replacement, are not included in the economic analysis either, because they are
negligible in comparison to the costs associated with buying the equipment itself
necessary for rainwater collection. Because the Radiance project involves converting
houses from a well water to a rainwater system there could be additional costs and
difficulties associated with installing the rainwater system such as excavation, grading,
and plumbing modifications which are difficult to quantify on a broad basis, but should
be considered are on a site-specific basis, and subsequently added to the economic
analysis.
30

35. Water Demand Modeling
Water Demand
An important consideration in determining the successful transition from municipal or
from well water to a rainwater system lies within the water usage patterns of the
Radiance Community. With their strict adherence to their goal of minimizing the impact
on the environment, many households have already adopted water conservation habits.
The water demand data for the current Radiance inhabitants reveals that many households
are already using less water than comparably sized households in other communities.
The data is further reinforced by a physical inspection of the Radiance Community.
Many of the households already maintain and utilize high-efficiency fixtures and
appliances inside their homes, and the irrigation demands of their landscaping has been
reduced by specifically choosing indigenous plants suited to the climate that require less
irrigation (Appendix D).
The Radiance subdivision has a varied pattern of water consumption among its
members’ houses; thus the design of a rainwater collection system here must account for
the disparate levels of water demand while ascertaining the feasibility of such a system
within the current consumption pattern of each house. Since it is impractical to run water-
demand models for each house individually, a series of models have been developed
addressing various combinations of water consumption patterns for indoor and outdoor
water use. These models establish the volume of rainwater that could be captured
effectively and stored throughout the year to aid in the reduction of the total water supply
required from the Radiance Water Supply Corporation. The models, as seen in Appendix
G, have been developed with three categories of consumption; low, average, and high,
each developed using water consumption data accumulated within the subdivision over
the last five years. Presumably most houses would fit within the definition of average-
usage scenario, unless an extreme consumption pattern has been recorded. The low and
high scenarios, respectively, have been developed to account for these extreme users. The
31

36. models have been further segregated into intended categories of use for the collected
rainwater. The ideal scenario uses rainwater to service the combined outdoor and indoor
water demand, but models have also been developed to study the ability of a rainwater
system to meet specific indoor or outdoor demands.
The models also help estimate the appropriate cistern dimensions necessary for an
independent rainwater system. Based on an aggregated monthly water
demand/consumption pattern acquired from the Radiance Water Supply Corporation, a
rainwater collection coefficient of 0.623 gallons of water per square foot roof area for
every inch of rainfall was used for calculating the total rainwater that could be collected.
A collection efficiency rate of 90% (ninety) was used to ensure that the model
incorporates concerns about losses occurring from phenomena such as roof surface
Figure 4. Consumption Scenarios
32

37. evaporation and with roof washing, among others. The rainfall data used in the model is
the monthly median rainfall rate in the region calculated, beginning in 1930, over a
seventy-five year period. The comprehensive nature of the data ensures that the model
incorporates climatic uncertainties that are typically linked to the effective functioning of
a rainwater system (Appendix D). The model also assumes that the average roof size in
the subdivision is around 1600 sq. ft.; a few optimized models were further tested for
effectiveness with larger roof sizes; these have been discussed Appendix G.
In order to simplify and to visually interpret the results of each model/scenario to be
discussed later, Figures 4 and 5 are presented. Figure 4 displays all scenario combinations
(low, average, and high consumption vs. indoor only, outdoor only, and combined indoor
and outdoor usage) adjacent to each other for ease of comparison. Each cell displays a
percentage in the upper left-hand corner, which indicates the percentage of demand that
can be met with rainwater alone. In the lower right-hand corner, a circle with one of three
color gradations is displayed to facilitate a quick reference of the practicality of a given
scenario combination. The practicality of a scenario is based on a few inter-related
factors and as a result of the factors overlapping; some residents may or may not
necessarily agree with the practicality designated. Factors considered are as follows:
1. Demand Satisfied vs. Tank Size/Cost :
• How much demand would be met, and would the return be significant enough
to render the tank required to contain that amount of water cost effective?
2. Excess Generated vs. Tank Size/Cost Increase:
• Will the amount of water collected be excessive to the point of unacceptable
spillage?
• Will the tank size require significant increase only to contain surplus rainfall
accumulated, not necessarily to amass the amount of water needed to meet the
demand for water?
3. Ultimate Practicality:
33

38. • Does a combination of factors 1 and 2 make the scenario seem particularly
unappealing?
• Does it simply satisfy so little demand that it is unwise to endure the necessary
process of installation and its comparably associated cost?
With the above stated factors considered, the gradations seen in Figures 4 and 5 indicate
an infeasible/very unpractical scenario, a moderately feasible/practical scenario, or a very
feasible/highly practical scenario. The practicality of a scenario, as seen below the tables
in Figures 4 and 5, increase as the color changes from red to green (left to right – very
unpractical to highly practical).
Results
Figure 5. Consumption Scenario Results
34

39. The analysis performed under the above mentioned consumption scenarios
concludes that it might be significantly advantageous for users under the average
consumption scenario to use a rainwater system for combined indoor/outdoor and for
indoor water use. Specific details of this analysis can be found in Appendix G. It is
additionally beneficial for houses with larger roof areas to install these systems as they
can meet up to half of their water needs through these rainwater systems. Under the low
consumption scenario almost all of the water requirement, both indoor and outdoor, can
be met using rainwater. An approximate roof size of 1850 square feet would meet 100%
water demand for these houses. The high-consumption scenario has a significantly higher
water demand from the previous scenarios. Given the cost of installation of these
systems, high-consumption houses using rainwater for indoor use was found to be most
feasible as with a large enough roof size, almost 34% (thirty-four) of indoor water use
could be met with this system.
.
35

40. Radiance Economic Report
Rainwater collection is a completely self-contained form of water supply. Unlike
municipal water utility supply where the cost of water is based on the volume supplied by
the utility company, rainwater collection the water is free and the cost is contained in the
price of the collection system equipment, and the installation of and the maintenance of
the system itself. An economic analysis of a rainwater collection system is based on the
price of the various systemic components and the replacement costs of the individual
parts, which, in turn are dependent on the volume of water to be collected and stored and
its determined function (Appendix J).
This section analyzes the economic feasibility of a residential system for the Radiance
community in Hays County. This project involves a fairly typical residential conversion
from well water supply to individual rainwater collection for the Radiance houses, with
the potential implementation throughout the entire community to be managed by the
existing Radiance Water Supply Corporation. Costs for the residential rainwater
collection systems are well established and can be obtained from several websites listed
in this report.
This economic assessment looks at two different scenario groups. The first scenario
group will analyze the cost of implementing a rainwater collection system in one
household and compare this cost with the reduction in water bill from the Radiance Water
Supply Corporation. The second scenario will analyze the cost of implementing
rainwater collection systems on a much larger scale in the Radiance community.
The Financial Model
A financial model was created to study the economic implications of rainwater
collection for the Radiance project. The model was designed to allow the user the
36

41. flexibility to update inputs and study the implications over a fifty-year time period. All
costs are inflation-adjusted assuming a rate of 2% (two) annually.
The Radiance project analysis studies the retrofit and the installation of rainwater
collection systems within a residential community for assorted levels of consumption and
of uses. This examination determines the financial feasibility of rainwater collection
through the comparison of rainwater system lifestyle costs to the combined current water
expenditures and the supplemental savings accrued by not replacing a well. The model
allows the input of the following variables: the cost of all components of rainwater
collection system, the interval of part replacement, a factor for installation and for
transportation costs as well as the average water bill under a household’s current supply.
See Figure 6 for a sample input box for low-consumption household.
Low Consumption
Square Feet 1600 Ave. monthly savings $ 9.05
Installation Factor 15%
Replacement
Intervals Replacement
Item Cost/Unit Total (years) Cost
Roof washer $ 850.00 $ 850.00 50 N/A
Tank (10,000g) $ 4,290.00 $ 4,290.00 50 N/A
Pump $ 585.00 $ 585.00 8 $ 585.00
Filter assembly $ 325.00 $ 325.00 50 N/A
3 & 5 micron filter* $ 100.00 $ 100.00 1 $ 100.00
UV light $ 675.00 $ 675.00 1.2 $ 80.00
Piping $ 3.00 $ 150.00 50 N/A
Electricity $ 0.07 $ 25.55 N/A N/A
* 1 year is a pack (12) 5 micrion filters and (4) 3 micron filters
Figure 6. Sample Results for Low-Consumption Household
37

42. Economic Analysis
The accuracy of the economic analysis relies on the quality of the input data. For the
purposes of this study, the inputs have been fixed based on information obtained through
research and through communication with specific project representatives. However, the
inherent value of the fiscal summation is in its flexibility to refine inputs based on clearer
current research and on a greater contemporary conception of projects’ needs and of their
planned direction. As previously mentioned, this analysis does not include any non-
monetary factors that may make rainwater harvesting increasingly attractive.
Implementation of Individual Rainwater Harvesting System
Rainwater collection systems for consumers with various needs including
irrigation (outdoor only) and potable (both indoor and outdoor) using costs to purchase,
to install, and to maintain the systems have been studied. The costs of systems will also
be analyzed for users with low, medium and high water demand and will be compared to
the cost savings from a reduced water utility bill.
Outdoor Indoor/Outdoor
Low Consumption $ 7,044 $ 7,936
Medium Consumption $ 7,528 $ 8,419
High Consumption $ 8,580 $ 9,471
Figure 7. Implementation Costs
There is a model in Appendix K that calculates the monthly water bill for a Radiance
customer based on the current rate structure. The cost of single rainwater collection
systems is shown in Figure 7.
Costs from this table represent the fixed, up-front cost of purchasing and of installing
a rainwater collection system. They include the tank itself, the filter assembly, the filters,
the UV lighting, the pumps, the roof washers and the piping. A tank size differs based on
38

43. the consumption rates. A 6,000-gallon tank was deemed appropriate for the low-
consumption users, an 8,000 gallon for medium-consumption users and an 11,000 one for
high-consumption users. These costs do not reflect the long-term maintenance costs such
as the replacing of filters and of pumps and the cost of electricity. These expenditures
will be included later in this report. The price of the outdoor systems does not include
filtration systems. The filtration of the indoor systems consists of a series of filters, 5-
micron and 3-micron, a UV light for disinfection and a filter board. A 15% (fifteen)
disbursement increase was added to these systems to defray installation and
transportation. This percentage is a variable and can be modified in the model for a
customer who wants to self-perform any or all of this work. Fiberglass has been selected
as the optimal tank material due to its long-term durability, its thermal properties and its
reasonable price, but alternatives do exist (Appendix J). A summary of all the expenses
provided in the tables above can be found in Appendix K.
In a single-home scenario, the cost of the rainwater systems can be compared to the
savings accrued on the water bill and on associated well water from using the Radiance
services. It should be duly noted that this expenditure differential would only be realized
if a very limited number of households implement a rainwater collection system because
the majority of the operational expenses of the water supply corporation are fixed.
Therefore, to generate the current amount of revenue (that which is required to support
the Radiance Water Supply Corporation) the corporation will be forced to raise rates on
the existing water usage to pay for its own fixed costs. This increase will theoretically
nullify any savings from a rainwater collection system on a community-wide application.
The community-wide application is discussed in a supplementary scenario.
39

44. Cost Analysis: Medium Consumption, Indoor & Outdoor
$35,000.00
$30,000.00 Costs
$25,000.00
Savings
Cumulative Cost ($)
$20,000.00
$15,000.00
$10,000.00
$5,000.00
$-
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Time (Yrs.)
Figure 8. Cost Anaylsis
Long-term expenses such as replacement costs and as electricity play a major role in
the economic feasibility of a rainwater collection system. A 2% (two) inflation factor
was also added. Figure 8 shows the fifty-year costs and savings for a medium-
consumption user with both indoor and outdoor uses. This figure shows that the
monetary outflow outweighs the savings over a fifty-year lifecycle of the system. The
two lines actually diverge, demonstrating that the recurring maintenance costs are higher
than the continued payment to the Radiance water supply corporation.
In total, nine figures were evaluated, varying the consumption from low, from
medium, and from high and varying the uses as indoor, outdoor and indoor and outdoor.
The indoor and outdoor scenario was also studied in conjunction with a larger roof
catchment surface. These nine figures can be found in the Appendix I. In only one
scenario did the savings from the rainwater collection system outweigh the expense of the
system: Low-Consumption with a large roof. This scenario is represented in Figure 9,
and demonstrates that the cost of the rainwater collection systems exceeded the savings
reaped in approximately the thirty-sixth year of operation, largely because the large roof
area provides sufficient catchment area for the low-consumption user to sustain average
water demands without supplement from the Radiance water supply corporation. This
40

45. independence will allow the user to forego the $22 monthly water service fee as well as
the municipal water fees.
Cost Analysis: Low Consumption, Indoor & Outdoor, Large Roof
$35,000.00
$30,000.00 Costs
$25,000.00
Savings
Cumulative Cost ($)
$20,000.00
$15,000.00
$10,000.00
$5,000.00
$-
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49
Tim e (Yrs.)
Figure 9. Cost Analysis
Implementation of Community-Wide Rainwater Harvesting System
Like most well water users, the Radiance community is faced with the imminent
necessity for a new well, as the existing loses its ability for adequate production to
support community. The cost of drilling a new well is loosely comparable to that of
installing rainwater collection systems in the Radiance community, an effort that will
lessen the strain on the existing well. However, the authors of this paper cannot forecast
precisely the level of decreased demand necessary to prolong the life of the existing well.
Figure 10 shows the cost of implementing rainwater collection systems for half of and for
all of the households, respectively, in the Radiance community, and the corresponding
gallons of rainwater used.
The cost of implementing rainwater collection systems over half of the homes in
Radiance slightly exceeds $136,000. This number assumes a 10% (ten) discount from
bulk purchasing savings, and from delivery and from installation savings. The
implementation expense of rainwater collection systems in all of the radiance homes is
41

46. roughly $258,000, which includes a discount factor of 15% (fifteen). All figures were
extrapolated from the average cost of a medium-consumption household for indoor and
outdoor use.
Cost of Systems Rainwater Used per Year (gal)
Half of Radiance $ 136,392 389,232
All of Radiance $ 257,630 778,464
Figure 10. Implementation Costs
A potential economic benefit of implementing rainwater collection systems over a
large portion of the community is the savings from not replacing the current well as the
strain on existing well is drastically diminished. The depth of drilling [to reach a water
source] will determine the expense of drilling a new well, but the likely sum centers
around $40,000. It appears that the amount of money required in attaining this $40,000
savings is much larger than the actual savings itself, deigning this scenario unfeasible
from an economic standpoint. As previously mentioned, the amount of water savings to
make the existing well sustainable is not known. Additional analysis should be
performed to further understand this issue. The table above estimates gallons of
rainwater used based on the medium consumption household for indoor and outdoor use
so that a future comparison can be made.
As many users in the surrounding areas continue to pump water at a very high rate,
the viability of well water is declining and ultimately may cease. In this scenario, the
cost of implementing rainwater collection systems to the Radiance community should be
compared to the foregone cost of other water sources.
42

47. Recommendations
Management Recommendations
To assist the homeowners, we recommend that the Radiance Water Supply
Corporation contact a rainwater system installer to consult. This consultant would
provide general design, management, routine maintenance guidelines and assistance for
all homes and would be on call if issues subsequently should arise. As each rainwater
system will be run independently, each individual homeowner will manage their own
collection system, and should monitor tank levels, maintain unobstructed gutters and
first-flush devices, change out filters regularly, maintain disinfection equipment and test
not only the water quality and but also the system functions regularly.
Monitoring Recommendations
The Texas Manual for Rainwater Harvesting recommends that both county health
department and city building code staff be consulted concerning the construction of the
rainwater collection system and the subsequent safe, sanitary operations. It is assumed
that the rainwater system installer will contact the necessary parties. Because the water
collected here will be potable, in accordance with the recommendations from the Texas
Manual for Rainwater Harvesting, we recommend that the harvested rainwater be tested
quarterly for fecal coliforms, pathogens, and pesticides by a commercial analytical
laboratory [Texas Manual for Rainwater Harvesting 2002]. Additionally, although
neither federal nor state guidelines exist for harvested water quality, one should check the
Environmental Protection Agency’s website [www.epa.gov/safewater/mcl.html] for a list
of the latest drinking water requirements before ordering specific tests. Most
commercial laboratories [consult your local Yellow Pages: Laboratories—Analytical and
Testing for a list of local testing laboratories] will test for pathogens, metals and
pesticides and the Texas Department of State Health Services
[www.dshs.state.tx.us/lab/default.shtm] will test for fecal coliforms.
43

48. Appendix A: Safety Codes
Excerpt from Texas Administrative Code:
Title 30, part 1, Chapter 290, Subchapter D, Rule § 290.39:
(a) Authority for requirements. Texas Health and Safety Code (THSC), Chapter 341,
Subchapter C prescribes the duties of the commission relating to the regulation and
control of public drinking water systems in the state. The statute requires that the
commission ensure that public water systems: supply safe drinking water in adequate
quantities, are financially stable and technically sound, promote use of regional and area-
wide drinking water systems, and review completed plans and specifications and business
plans for all contemplated public water systems not exempted by THSC, §341.035(d).
The statute also requires the commission be notified of any subsequent material changes,
improvements, additions, or alterations in existing systems and, consider compliance
history in approving new or modified public water systems.
(b) Reason for this subchapter and minimum criteria. This subchapter has been adopted to
ensure regionalization and area-wide options are fully considered, the inclusion of all
data essential for comprehensive consideration of the contemplated project, or
improvements, additions, alterations, or changes thereto and to establish minimum
standardized public health design criteria in compliance with existing state statutes and in
accordance with good public health engineering practices. In addition, minimum
acceptable financial, managerial, technical, and operating practices must be specified to
ensure that facilities are properly operated to produce and distribute a safe, potable water.
(c) Required actions and approvals prior to construction. A person may not begin
construction of a public drinking water supply system unless the executive director
determines the following requirements have been satisfied and approves construction of
the proposed system.
(1) A person proposing to install a public drinking water system within the
extraterritorial jurisdiction of a municipality; or within 1/2-mile of the corporate
boundaries of a district, or other political subdivision providing the same service; or
within 1/2-mile of a certificated service area boundary of any other water service
provider shall provide to the executive director evidence that:
(A) written application for service was made to that provider; and
(B) all application requirements of the service provider were satisfied, including the
payment of related fees.
(2) A person may submit a request for an exception to the requirements of paragraph (1)
of this subsection if the application fees will create a hardship on the person. The request
must be accompanied by evidence documenting the financial hardship.
(3) A person who is not required to complete the steps in paragraph (1) of this
subsection, or who completes the steps in paragraph (1) of this subsection and is denied
service or determines that the existing provider's cost estimate is not feasible for the
development to be served, shall submit to the executive director:
(A) plans and specifications for the system; and
(B) a business plan for the system.
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49. (d) Submission of plans.
(1) Plans, specifications, and related documents will not be considered unless they have
been prepared under the direction of a licensed professional engineer. All engineering
documents must have engineering seals, signatures, and dates affixed in accordance with
the rules of the Texas Board of Professional Engineers.
(2) Detailed plans must be submitted for examination at least 30 days prior to the time
that approval, comments or recommendations are desired. From this, it is not to be
inferred that final action will be forthcoming within the time mentioned.
(3) The limits of approval are as follows.
(A) The commission's public drinking water program furnishes consultation services as
a reviewing body only, and its licensed professional engineers may neither act as design
engineers nor furnish detailed estimates.
(B) The commission's public drinking water program does not examine plans and
specifications in regard to the structural features of design, such as strength of concrete or
adequacy of reinforcing. Only the features covered by this subchapter will be reviewed.
(C) The consulting engineer and/or owner must provide surveillance adequate to assure
that facilities will be constructed according to approved plans and must notify the
executive director in writing upon completion of all work. Planning materials shall be
submitted to the Texas Commission on Environmental Quality, Water Supply Division,
MC 153, P.O. Box 13087, Austin, Texas 78711-3087.
(e) Submission of planning material. In general, the planning material submitted shall
conform to the following requirements.
(1) Engineering reports are required for new water systems and all surface water
treatment plants. Engineering reports are also required when design or capacity
deficiencies are identified in an existing system. The engineering report shall include, at
least, coverage of the following items:
(A) statement of the problem or problems;
(B) present and future areas to be served, with population data;
(C) the source, with quantity and quality of water available;
(D) present and estimated future maximum and minimum water quantity demands;
(E) description of proposed site and surroundings for the water works facilities;
(F) type of treatment, equipment, and capacity of facilities;
(G) basic design data, including pumping capacities, water storage and flexibility of
system operation under normal and emergency conditions; and
(H) the adequacy of the facilities with regard to delivery capacity and pressure
throughout the system.
(2) All plans and drawings submitted may be printed on any of the various papers which
give distinct lines. All prints must be clear, legible and assembled to facilitate review.
(A) The relative location of all facilities which are pertinent to the specific project shall
be shown.
(B) The location of all abandoned or inactive wells within 1/4-mile of a proposed well
site shall be shown or reported.
(C) If staged construction is anticipated, the overall plan shall be presented, even
though a portion of the construction may be deferred.
(D) A general map or plan of the municipality, water district, or area to be served shall
accompany each proposal for a new water supply system.
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50. (3) Specifications for construction of facilities shall accompany all plans. If a process or
equipment which may be subject to probationary acceptance because of limited
application or use in Texas is proposed, the executive director may give limited approval.
In such a case, the owner must be given a bonded guarantee from the manufacturer
covering acceptable performance. The specifications shall include a statement that such a
bonded guarantee will be provided to the owner and shall also specify those conditions
under which the bond will be forfeited. Such a bond will be transferrable. The bond shall
be retained by the owner and transferred when a change in ownership occurs.
(4) A copy of each fully executed sanitary control easement and any other
documentation demonstrating compliance with §290.41(c)(1)(F) of this title (relating to
Water Sources) shall be provided to the executive director prior to placing the well into
service. Each original easement document, if obtained, must be recorded in the deed
records at the county courthouse. Section 290.47(c) of this title (relating to Appendices)
includes a suggested form.
(5) Construction features and siting of all facilities for new water systems and for major
improvements to existing water systems must be in conformity with applicable
commission rules.
(f) Submission of business plans. The prospective owner of the system or the person
responsible for managing and operating the system must submit a business plan to the
executive director that demonstrates that the owner or operator of the system has
available the financial, managerial, and technical capability to ensure future operation of
the system in accordance with applicable laws and rules. The executive director may
order the prospective owner or operator to demonstrate financial assurance to operate the
system in accordance with applicable laws and rules as specified in Chapter 37,
Subchapter O of this title (relating to Financial Assurance for Public Drinking Water
Systems and Utilities), or as specified by commission rule, unless the executive director
finds that the business plan demonstrates adequate financial capability. A business plan
shall include the information and be presented in a format prescribed by the executive
director. For community water systems, the business plan shall contain, at a minimum,
the following elements:
(1) description of areas and population to be served by the potential system;
(2) description of drinking water supply systems within a two-mile radius of the
proposed system, copies of written requests seeking to obtain service from each of those
drinking water supply systems, and copies of the responses to the written requests;
(3) time line for construction of the system and commencement of operations;
(4) identification of and costs of alternative sources of supply;
(5) selection of the alternative to be used and the basis for that selection;
(6) identification of the person or entity which owns or will own the drinking water
system and any identifiable future owners of the drinking water system;
(7) identification of any other businesses and public drinking water system(s) owned or
operated by the applicant, owner(s), parent organization, and affiliated organization(s);
(8) an operations and maintenance plan which includes sufficient detail to support the
budget estimate for operation and maintenance of the facilities;
(9) assurances that the commitments and resources needed for proper operation and
maintenance of the system are, and will continue to be, available, including the
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51. qualifications of the organization and each individual associated with the proposed
system;
(10) for retail public utilities as defined by Texas Water Code (TWC), §13.002:
(A) projected rate revenue from residential, commercial, and industrial customers; and
(B) pro forma income, expense, and cash flow statements;
(11) identification of any appropriate financial assurance, including those being offered
to capital providers;
(12) a notarized statement signed by the owner or responsible person that the business
plan has been prepared under his direction and that he is responsible for the accuracy of
the information; and
(13) other information required by the executive director to determine the adequacy of
the business plan or financial assurance.
(g) Business plans not required. A person is not required to file a business plan if the
person:
(1) is a county;
(2) is a retail public utility as defined by TWC, §13.002, unless that person is a utility as
defined by that section;
(3) has executed an agreement with a political subdivision to transfer the ownership and
operation of the water supply system to the political subdivision; or
(4) is a noncommunity nontransient water system and the person has demonstrated
financial assurance under THSC, Chapter 361 or 382 or TWC, Chapter 26.
(h) Beginning and completion of work.
(1) No person may begin construction on a new public water system before receiving
written approval of plans and specifications and, if required, approval of a business plan
from the executive director. No person may begin construction of modifications to a
public water system without providing notification to the executive director and
submitting and receiving approval of plans and specifications if requested in accordance
with subsection (j) of this section.
(2) The executive director shall be notified in writing by the design engineer or the
owner before construction is started.
(3) Upon completion of the water works project, the engineer or owner shall notify the
executive director in writing as to its completion and attest to the fact that the completed
work is substantially in accordance with the plans and change orders on file with the
commission.
(i) Changes in plans and specifications. Any addenda or change orders which may
involve a health hazard or relocation of facilities, such as wells, treatment units, and
storage tanks, shall be submitted to the executive director for review and approval.
(j) Changes in existing systems or supplies. Public water systems shall notify the
executive director prior to making any significant change or addition to the system's
production, treatment, storage, pressure maintenance, or distribution facilities. Public
water systems shall submit plans and specifications for the proposed changes upon
request. Changes to an existing disinfection process at a treatment plant that treats surface
water or groundwater that is under the direct influence of surface water shall not be
instituted without the prior approval of the executive director.
(1) The following changes are considered to be significant:
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52. (a) proposed changes to existing systems which result in an increase or decrease in
production, treatment, storage, or pressure maintenance capacity;
(B) proposed changes to the disinfection process used at plants that treat surface water or
groundwater that is under the direct influence of surface water including changes
involving the disinfectants used, the disinfectant application points, or the disinfectant
monitoring points;
(C) proposed changes to the type of disinfectant used to maintain a disinfectant
residual in the distribution system;
(D) proposed changes in existing distribution systems when the change is greater than
10% of the existing distribution capacity or 250 connections, whichever is smaller, or
results in the water system's inability to comply with any of the applicable capacity
requirements of §290.45 of this title (relating to Minimum Water System Capacity
Requirements); and
(E) any other material changes specified by the executive director.
(2) The executive director shall determine whether engineering plans and specifications
will be required after reviewing the initial notification regarding the nature and extent of
the modifications.
(A) Upon request of the executive director, the water system shall submit plans and
specifications in accordance with the requirements of subsection (d) of this section.
(B) Unless plans and specifications are required by Chapter 293 of this title (relating to
Water Districts), the executive director will not require another state agency or a political
subdivision to submit planning material on distribution line improvements if the entity
has its own internal review staff and complies with all of the following criteria:
(i) the internal review staff includes one or more licensed professional engineers that
are employed by the political subdivision and must be separate from, and not subject to
the review or supervision of, the engineering staff or firm charged with the design of the
distribution extension under review;
(ii) a licensed professional engineer on the internal review staff determines and
certifies in writing that the proposed distribution system changes comply with the
requirements of §290.44 of this title (relating to Water Distribution) and will not result in
a violation of any provision of §290.45 of this title;
(iii) the state agency or political subdivision includes a copy of the written
certification described in this subparagraph with the initial notice that is submitted to the
executive director.
(C) Unless plans and specifications are required by Chapter 293 of this title, the
executive director will not require planning material on distribution line improvements
from any public water system that is required to submit planning material to another state
agency or political subdivision that complies with the requirements of subparagraph (B)
of this paragraph. The notice to the executive director must include a statement that a
state statute or local ordinance requires the planning materials to be submitted to the other
state agency or political subdivision and a copy of the written certification that is required
in subparagraph (B) of this paragraph.
(3) If a certificate of convenience and necessity (CCN) is required or must be amended,
the CCN application must be included with the notice to the executive director.
(k) Planning material acceptance. Planning material for improvements to an existing
system which does not meet the requirements of all sections of this subchapter will not be
48