Community and Regional Planning Program

University of Texas School of Architecture

Austin, Texas

Rainwater Harvesting Systems for Residential and Commercial

Systems:

Seaholm Power Plant and Radiance Community

Urban Environmental Analysis

CRP 383: Fall 2005

Community and Regional Planning ProgramUniversity of Texas School of Architecture

Austin, Texas

July, 2006

Analysis Prepared and Presented By:

Professor:Kent Butler

Ahmed Abukhater

Jason Fryer

Ashley FrancisKyle Irons

Andrew JuddWonsoo Lee

Nathan MeadeVipin Nambiar

Mary-Elaine Sotos

July, 2006

Additional Research:

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

Urban Environmental Analysis

CRP 383: Fall 2005

Community and Regional Planning ProgramUniversity of Texas School of Architecture

Austin, Texas

July, 2006

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 44 sedoC ytefaS :A xidneppA 15 sedoC htlaeH :B xidneppA 35 etiS mlohaeS :C xidneppA 55 ataD detaleR retaW saxeT :D xidneppA 85 ledoM dnameD mlohaeS :E xidneppA

Appendix F: Stormwater Considerations at Seaholm 67 96 soiranecS ecnaidaR :G xidneppA 47 gniledoM ecnaidaR :H xidneppA

Appendix I: Radiance Economic Analysis 80Appendix J: Notes on Cost Analysis and Cisterns 85 Appendix K: Cost Analysis and Monthly Savings 87

09 sisylanA tsoC mlohaeS :L xidneppA

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

[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

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

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

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

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).

Figure 1. Chinese Cisterns for Rainwater Storage

5

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,

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

Figure 2. Residential Rainwater System

6

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

• 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

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

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

accommodate the excess water runoff. Technical studies must be conducted to evaluate the

adequacy and the capacity of the infrastructure in both projects.

11

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

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

streams through two flanking rows of

Figure 1. Aerial View: Seaholm Power Plant

13

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

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

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

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

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

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 3. Rainwater Collection Areas

Figure 4. Rainwater Storage Locations

18

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

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

Figure 5. Proposed Landscaping

19

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

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

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

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

toilets, have longer payback

periods due to the gratuitous

costs associated with the

additional storage and

conveyance equipment

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

Figure 6. Payback Periods

Years to Achieve Return on Investment Water Price Inflation (%)

Scenario 2 3 4 5 A 29 23 20 19 B 27 21 20 18 C 34 29 26 22 D 46 36 30 27

23

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

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

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

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

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

Figure 1. Typical Radiance Household

27

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

of conventional landscaping. Figure 2. Permeable Pavement

28

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

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

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

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

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

• 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

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

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

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.

Figure 6. Sample Results for Low-Consumption Household

Low Consumption Square Feet 1600 Ave. monthly savings $ 9.05

Installation Factor 15%

Item Cost/Unit Total

Replacement Intervals (years)

Replacement 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

37

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

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

Figure 7. Implementation Costs

38

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

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

Cost Analysis: Medium Consumption, Indoor & Outdoor

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 8. Cost Anaylsis

40

independence will allow the user to forego the $22 monthly water service fee as well as

the municipal water fees.

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

Cost Analysis: Low Consumption, Indoor & Outdoor, Large Roof

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 9. Cost Analysis

41

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.

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.

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

42

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

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.

44

(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.

45

(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

46

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:

47

(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

considered unless the necessary modifications for correcting the deficiencies are included in the proposed improvements, or unless the executive director determines that reasonable progress is being made toward correcting the deficiencies and no immediate health hazard will be caused by the delay. (l) Exceptions. Requests for exceptions to one or more of the requirements in this subchapter shall be considered on an individual basis. Any water system which requests an exception must demonstrate to the satisfaction of the executive director that the exception will not compromise the public health or result in a degradation of service or water quality. (1) The exception must be requested in writing and must be substantiated by carefully documented data. The request for an exception shall precede the submission of engineering plans and specifications for a proposed project for which an exception is being requested. (2) Any exception granted by the commission is subject to revocation. (3) Any request for an exception which is not approved by the commission in writing is denied. (m) Notification of system startup or reactivation. The owner or responsible official must provide written notification to the commission of the startup of a new public water supply system or reactivation of an existing public water supply system. This notification must be made immediately upon meeting the definition of a public water system as defined in §290.38 of this title (relating to Definitions). (n) The commission may require the owner or operator of a public drinking water supply system that was constructed without the approval required by (THSC), §341.035, that has a history of noncompliance with (THSC), Chapter 341, Subchapter C or commission rules, or that is subject to a commission enforcement action to take the following action: (1) provide the executive director with a business plan that demonstrates that the system has available the financial, managerial, and technical resources adequate to ensure future operation of the system in accordance with applicable laws and rules. The business plan must fulfill all the requirements for a business plan as set forth in subsection (f) of this section; (2) provide adequate financial assurance of the ability to operate the system in accordance with applicable laws and rules. The executive director will set the amount of the financial assurance, after the business plan has been reviewed and approved by the executive director. (A) The amount of the financial assurance will equal the difference between the amount of projected system revenues and the projected cash needs for the period of time prescribed by the executive director. (B) The form of the financial assurance will be as specified in Chapter 37, Subchapter O of this title and will be as specified by the executive director. (C) If the executive director relies on rate increases or customer surcharges as the form of financial assurance, such funds shall be deposited in an escrow account as specified in Chapter 37, Subchapter O of this title and released only with the approval of the executive director. Source Note: The provisions of this §290.39 adopted to be effective October 1, 1992, 17 TexReg 6455; amended to be effective November 3, 1995, 20 TexReg 8620; amended to

49

be effective February 4, 1999, 24 TexReg 731; amended to be effective September 13, 2000, 25 TexReg 8880; amended to be effective May 16, 2002, 27 TexReg 4127; amended to be effective February 19, 2004, 29 TexReg 1373

50

Appendix B: Health Codes Excerpt from Texas Health and Safety Code § 341.036. SANITARY DEFECTS AT PUBLIC DRINKING WATER SUPPLY SYSTEMS. (a) A sanitary defect at a public drinking water supply system that obtains its water supply from underground sources shall be immediately corrected. (b) A public drinking water supply system furnishing drinking water from underground sources may not be established in a place subject to possible pollution by floodwaters unless the system is adequately protected against flooding. (c) Suction wells or suction pipes used in a public drinking water supply system must be constantly protected by practical safeguards against surface and subsurface pollution. (d) Livestock may not be permitted to enter or remain in the wellhouse enclosure of a public drinking water supply system. (e) Public drinking water distribution lines must be constructed of impervious materials with tight joints and must be a reasonably safe distance from sewer lines. (f) Water from a surface public drinking water supply may not be made accessible or delivered to a consumer for drinking purposes unless the water has been treated to make it safe for human consumption. Water treatment plants, including aeration, coagulation, mixing, settling, filtration, and chlorinating units, shall be of a size and type prescribed by good public health engineering practices. (g) A clear water reservoir shall be covered and be of a type and construction that prevents the entrance of dust, insects, and surface seepage. Acts 1989, 71st Leg., ch. 678, § 1, eff. Sept. 1, 1989. § 341.037. PROTECTION OF BODIES OF WATER FROM SEWAGE. The commission shall enforce state laws and take other necessary action to protect a spring, well, pond, lake, reservoir, or other stream in this state from any condition or pollution that results from sewage and that may endanger the public health. Acts 1989, 71st Leg., ch. 678, § 1, eff. Sept. 1, 1989. Amended by Acts 1995, 74th Leg., ch. 76, § 11.15, eff. Sept. 1, 1995. § 341.038. PROTECTION OF IMPOUNDED WATER FROM DISEASE-BEARING MOSQUITOES. A person that impounds water for public use shall cooperate with the commission and local departments of health to control disease-bearing mosquitoes on the impounded area. Acts 1989, 71st Leg., ch. 678, § 1, eff. Sept. 1, 1989. Amended by Acts 1995, 74th Leg., ch. 76, § 11.15, eff. Sept. 1, 1995.

51

§ 341.039. GRAYWATER STANDARDS. (a) The commission by rule shall adopt and implement minimum standards for the use and reuse of graywater for: (1) irrigation and other agricultural purposes; (2) domestic use, to the extent consistent with Subsection (c); (3) commercial purposes; and (4) industrial purposes. (b) The standards adopted by the commission under Subsection (a) must assure that the use of graywater is not a nuisance and does not damage the quality of surface water and groundwater in this state. (c) The commission may not require a permit for the domestic use of less than 400 gallons of graywater each day if the graywater: (1) originates from a private residence; (2) is used by the occupants of that residence for gardening, composting, or landscaping at the residence; (3) is collected using a system that overflows into a sewage collection or on-site wastewater treatment and disposal system; (4) is stored in tanks that: (A) are clearly labeled as nonpotable water; (B) restrict access, especially to children; and (C) eliminate habitat for mosquitoes and other vectors; (5) uses piping clearly identified as a nonpotable water conduit, including identification through the use of purple pipe, purple tape, or similar markings; (6) is generated without the formation of ponds or pools of graywater; (7) does not create runoff across the property lines or onto any paved surface; and (8) is distributed by a surface or subsurface system that does not spray into the air. (d) Each builder is encouraged to: (1) install plumbing in new housing in a manner that provides the capacity to collect graywater from all allowable sources; and (2) design and install a subsurface graywater system around the foundation of new housing in a way that minimizes foundation movement or cracking. (e) In this section, "graywater" means wastewater from clothes-washing machines, showers, bathtubs, hand-washing lavatories, and sinks that are not used for disposal of hazardous or toxic ingredients. The term does not include wastewater: (1) that has come in contact with toilet waste; (2) from the washing of material, including diapers, soiled with human excreta; or (3) from sinks used for food preparation or disposal. Acts 1989, 71st Leg., ch. 678, § 1, eff. Sept. 1, 1989. Amended by Acts 1993, 73rd Leg., ch. 233, § 2, eff. Aug. 30, 1993; Acts 1995, 74th Leg., ch. 76, § 11.16, eff. Sept. 1, 1995; Acts 2003, 78th Leg., ch. 689, § 2, eff. Sept. 1, 2003.

52

Appendix C: Seaholm Site Conditions Existing Conditions

Area Square

Feet Power Plant Upper Roof 21,845 Power Plant Lower Roof 13,310 Surface Parking / Circulation 109,400 Fuel Building Roof 1,185 Total Impervious Cover 145,740

Area/Volume Square

Feet Fuel Oil Tanks (estimated) 8,100Surge Tanks - South (estimated) 544

Area/Volume Cubic Feet

Surge Tanks - South (estimated) 7,616Fuel Oil Tanks (estimated) 283,500 Future Conditions

Area Square

Feet Power Plant Upper Roof 21,845 Power Plant Lower Roof 13,310 Fuel Building Roof 1,185 Roadways/Paving 61,990 Site Pedestrian Paving 25,395 North Plaza Pavers 64,534 South Terrace Pavers 19,180 Fountains 12,820 Office Roof (est.) 30,500 Residential Tower Roof (est.) 10,500 Total Impervious Cover (estimated) 261,259

53

Other Areas - Future Square

Feet Number Fountains 12,820 Landscaping (sod/ native plants) 65,248 Trees (not in landscape SF) 81

Land Use Square

Feet Seaholm - various uses See Above Fuel Building (Retail) 1,048 Retail 10,000 Residential 90,000 Commercial/Office 60,000 Parking ???

54

Appendix D: Texas Water Related Data

Figure 1. Average Monthly Evapotranspiration for Texas Cities

Figure 2. Plant Water Use Coefficients

55

Info

rmat

ion

prov

ided

, but

can

be

chan

ged

Info

rmat

ion

to b

e in

put b

y us

er

Out

puts

ETm

onth

ly *

Kc *

0.6

23

* A

lan

dsca

pe =

Ou

tdoo

r W

ater

Dem

and

Vol

um

e (g

allo

ns)

W

here

:

E

T mon

thly

= M

onth

ly E

vapo

trans

pira

tion

Am

ount

(inc

hes)

=

(g

iven

bel

ow fo

r Aus

tin)

K

c =

Pla

nt W

ater

Use

Coe

ffici

ent

=

0.5

(see

cha

rt)

0.75

0.

2

To

tal

(s.f.

)P

ortio

nof

Tot

al

A

land

scap

e =

Land

scap

e A

rea

6524

8 0.

7 =

4567

3.6

(med

ium

)

0.

2 =

1304

9.6

(hig

h)

0.1

= 65

24.8

(low

)

C

onve

rsio

n fro

m in

/ft^2

to

3 26.0

=

snol lag

ET-

Mon

thly

Eva

potra

nspi

ratio

n A

mou

nt fo

r Aus

tin, T

exas

(inc

hes)

Ja

nuar

y Fe

brua

ryM

arch

Apr

ilM

ayJu

neJu

lyA

ugus

tS

epte

mbe

rO

ctob

erN

ovem

ber

Dec

embe

rTo

tal

0.56

0.76

2.67

3.21

4.36

5.92

6.85

6.61

3.4

2.47

1.44

0.27

38.5

2

leg

end

Figu

re 3

. Pa

n E

vapo

ratio

n R

ates

56

Nee

ds o

f Lan

dsca

pe (g

allo

ns)

Janu

ary

Febr

uary

Mar

chA

pril

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Nov

embe

rD

ecem

ber

Tota

l Nee

dsm

ediu

m79

6710

813

3798

745

670

6203

184

226

9745

794

043

4837

335

141

2048

738

4154

8037

high

3415

4634

1628

019

573

2658

536

097

4176

740

304

2073

115

061

8780

1646

2348

73

low

45

561

821

7126

1035

4548

1355

6953

7427

6420

0811

7122

031

316

tota

l11

837

1606

5 56

438

6785

2 92

161

1251

35

1447

94

1397

20

7186

8 52

210

3043

8 57

07

8142

26

Pan

Eva

pora

tion

Rat

es to

cal

cula

te lo

ss fr

om fo

unta

ins

(inch

es)

Janu

ary

Febr

uary

M

arch

Apr

il M

ay

June

July

A

ugus

tS

epte

mbe

rO

ctob

erN

ovem

ber

Dec

embe

rTo

tal

0.7

0.6

2.1

2.3

1.4

3.7

6.2

5.3

2.5

1.9

1.4

0.4

52.8

S

ize

of fo

unta

in b

ase

= 12

820

ft^2

co

nver

sion

=

0.62

3

w

ind

evap

. fac

tor

= 1.

2

Nee

ds (g

allo

ns)

Janu

ary

Febr

uary

M

arch

Apr

il M

ay

June

July

A

ugus

tS

epte

mbe

rO

ctob

erN

ovem

ber

Dec

embe

rTo

tal

6325

.657

50.5

1983

9.4

2242

7.1

1351

3.8

3584

5.0

5970

9.8

5089

2.3

2376

8.9

1859

3.4

1303

4.6

3737

.927

3438

.1

Figu

re 5

. Aus

tin, T

X P

an E

vapo

ratio

n R

ates

Figu

re 6

. L

ands

cape

Nee

ds

Jan

Fe

b M

ar

Apr

M

ay

June

Ju

ly

Aug

S

ept

Oct

N

ov

Dec

To

tal P

reci

p. O

ver 7

5 ye

ars

for a

Giv

en M

onth

14

9.56

158.

8113

4.04

191.

0127

9.41

247.

5617

0.73

169.

8123

9.58

224.

4719

5.26

166.

55 4747

4747

4757

5747

4747

5757

tnuoC M

onth

ly A

vg.

1.99

2.12

1.81

2.58

3.78

3.30

2.28

2.29

3.24

3.03

2.64

2.25

Mon

thly

Avg

. Per

cent

iles

1st (

100%

) 1.

992.

121.

812.

583.

783.

302.

282.

293.

243.

032.

642.

252n

d (7

5%)

1.50

1.59

1.36

1.94

2.83

2.48

1.71

1.72

2.43

2.28

1.98

1.69

3rd

(50%

) 1.

001.

060.

911.

291.

891.

651.

141.

151.

621.

521.

321.

134t

h (2

5%)

0.50

0.53

0.45

0.65

0.94

0.83

0.57

0.57

0.81

0.76

0.66

0.56

Figu

re 4

. Aus

tin, T

X A

vera

ge R

ainf

all D

Ata

57

Appendix E: Seaholm Demand Model

Provided below are descriptions of each water demand scenario examined, as well

as the models and the graphs necessary to evaluate them. Assuming that only non-

potable demands are considered, the following diagram explains the basic variables and

their affects on the model graphically:

Figure 1. Water Demand Scenario

We developed spreadsheet modeling to examine the varying scales of rainwater

collection. To further test our models, we developed four different design scenarios. The

four models of water demand can be described as follows:

• 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

58

Scenario A : Irrigation with 30,000 gallons added storage

This scenario evaluated only the landscape irrigation demands when compared to

the volume of rainwater collected solely from the existing Seaholm Power Plant building

itself. Scenario A would require the least additional amount of equipment and of

maintenance. Minor renovations of the existing gutter systems would be necessary and

only approximately 30,000 to 35,000 gallons of additional storage tanks would be

needed. It was found that the rooftop area was insufficient to provide the capacity to

meet all of the landscape irrigation demands, though the system was able to satisfy

between 58% (fifty-eight) and 59% (fifty-nine) of the total demands. Also, due to the

increased demand and decreased supply in the summer months, the stored water level

fluctuated heavily. The demands also exceeded the amount of water stored and captured

between July and November, requiring additional use of municipal water, Figure 2.

Variable Notes Value

Total Rooftop Collection Area (s.f.) Power plant roof only 35,160

Total Cistern Capacity (gallons) Existing cistern + 30,000 gallons extra storage 87,000

Water Demands Evaluated (gallons per year) Landscape irrigation only 814,230

Percentage of Demands Met with Rainwater

In order to meet optimum system flow 58.5%

Total Rainwater Harvested (gallons per year) 476,320

Total Municipal Water Used (gallons per year) 337,900

Total Rainwater Spilled (gallons per year) 0

Figure 2. Scenario A: Results

59

Lan

dsca

pe w

ater

dem

ands

onl

y, e

xist

ing

pow

er p

lant

roo

f col

lect

ion

area

onl

y M

onth

La

ndsc

ape

Dem

ands

(G

allo

ns)

Tota

l D

eman

d M

et

(Gal

lons

)

Med

ian

Rai

nfal

l (In

ches

)

Rai

nfal

l C

olle

cted

(G

allo

ns)

Rai

nwat

er

Spill

ed

(Gal

lons

)

End-

of-M

onth

St

orag

e

(250

00 g

al. t

o st

art)

Mun

icip

al

Wat

er U

sed

(Gal

lons

)

25,0

00

Jan

11,8

37

6,92

5 1.

44

28,3

84

46

,460

4,

912

Feb

16,0

65

9,39

8 1.

90

37,4

52

74

,514

6,

667

Mar

56

,438

33

,016

1.

63

32,1

30

73

,627

23

,422

Apr

67

,852

39

,694

2.

06

40,6

06

74

,539

28

,159

May

92

,161

53

,914

3.

19

62,8

79

83

,505

38

,247

Jun

125,

135

73,2

04

2.36

46

,519

56,8

19

51,9

31

Jul

144,

794

84,7

04

1.27

25

,033

-2,8

52

60,0

89

Aug

13

9,72

0 81

,736

1.

59

31,3

41

-5

3,24

7 57

,984

Se

p 71

,868

42

,043

2.

82

55,5

86

-3

9,70

4 29

,825

O

ct

52,2

10

30,5

43

2.46

48

,490

-21,

757

21,6

67

Nov

30

,438

17

,806

1.

64

32,3

27

-7

,236

12

,632

D

ec

5,70

7 3,

339

1.81

35

,678

25,1

03

2,36

8

SU

MS

814,

226

476,

322

24.1

7

476,

425

0

337,

904

Figu

re 3

. Sc

enar

io A

: Wat

er D

eman

d M

odel

60

Scenario B: Irrigation with office bldg. and 60,000 gallons added storage

This scenario evaluated only the landscape irrigation demands when compared

with the rainwater collected from the existing Seaholm Power Plant building and to the

proposed office building. Scenario B would require a small amount of additional

equipment and maintenance than Scenario A. In addition to the minor renovations of the

existing gutter systems, a new gutter system and piping from the office building would be

necessary. Also, the increase in roof area requires the addition of approximately 60,000

gallons of additional storage tanks. It was determined that the increased rooftop area was

sufficient to provide capacity enough to meet all of the landscape irrigation demands

resulting in the rainwater satisfying 100% of the projected demands. However, the

rainwater collected exceeded the water demand and consequently, the tanks spilled

approximately 40,000 gallons between February and May, see Figure 4.

Variable Notes Value

Total Rooftop Collection Area (s.f.) Power plant & office roofs 65,660

Total Cistern Capacity (gallons) Existing cistern + 60,000 gallons extra storage 117,000

Water Demands Evaluated (gallons per year) Landscape irrigation only 814,230

Percentage of Demands Met with Rainwater

In order to meet optimum system flow 100%

Total Rainwater Harvested (gallons per year) 814,230

Total Municipal Water Used (gallons per year) 0

Total Rainwater Spilled (gallons per year) 39,870

Figure 4. Scenario B: Results

61

Lan

dsca

pe w

ater

dem

ands

onl

y, e

xist

ing

pow

er p

lant

& p

ropo

sed

offic

e ro

of c

olle

ctio

n ar

ea

Mon

th

Land

scap

e D

eman

ds

(Gal

lons

)

Tota

l D

eman

d M

et

(Gal

lons

)

Med

ian

Rai

nfal

l (In

ches

)

Rai

nfal

l C

olle

cted

(G

allo

ns)

Rai

nwat

er

Spill

ed

(Gal

lons

)

End-

of-M

onth

St

orag

e

(250

00 g

al. t

o st

art)

Mun

icip

al

Rai

nwat

er U

sed

(Gal

lons

)

25,0

00

Jan

11,8

37

11,8

37

1.44

53

,010

66,1

73

0

Feb

16,0

65

16,0

65

1.90

69

,944

3,

053

117,

000

0

Mar

56

,438

56

,438

1.

63

60,0

05

3,56

7 11

7,00

0 0

Apr

67,8

52

67,8

52

2.06

75

,834

7,

982

117,

000

0

May

92

,161

92

,161

3.

19

117,

433

25,2

72

117,

000

0

Jun

125,

135

125,

135

2.36

86

,878

78,7

43

0

Jul

144,

794

144,

794

1.27

46

,752

-19,

299

0

Aug

139,

720

139,

720

1.59

58

,532

-100

,487

0

Sep

71,8

68

71,8

68

2.82

10

3,81

2

-68,

543

0

Oct

52

,210

52

,210

2.

46

90,5

59

-3

0,19

4 0

Nov

30

,438

30

,438

1.

64

60,3

73

-2

59

0

Dec

5,

707

5,70

7 1.

81

66,6

31

60

,664

0

SUM

S 81

4,22

6 81

4,22

6 24

.17

88

9,76

4 39

,874

0

Figu

re 5

. Sc

enar

io B

: Wat

er D

eman

d M

odel

62

Scenario C: Irrigation and fountains with 100,000 gallons additional storage

This scenario evaluated the demands of landscape irrigation and of decorative

fountains when compared with the rainwater that could be collected from the existing

Seaholm Power Plant building in addition to the proposed office building. Scenario C

would require similar amounts of additional equipment and maintenance as in Scenario

B. Additional maintenance would also result in the use of the water to fill fountains,

which, because they in the public domain, must be more intensely filtered and tested.

The water capture area would also subsequently increase to approximately 100,000

gallons. It was determined that the additional rooftop area was still insufficient to

provide the capacity required to meet all of the outdoor water demands, though the

system was able to supply between 81% (eighty-one) and 82% (eighty-two) of the total

demands. The demands exceeded the amount of water captured and stored between July

and November, thus requiring the additional use of municipal water, Figure 6.

Variable Notes Value

Total Rooftop Collection Area (s.f.) Power plant & office roofs 65,660

Total Cistern Capacity (gallons) Existing cistern + 100,000 gallons extra storage 157,000

Water Demands Evaluated (gallons per year)

Landscape irrigation and fountain only 1,087,660

Percentage of Demands Met with Rainwater

In order to meet optimum system flow 81.8%

Total Rainwater Harvested (gallons per year) 889,710

Total Municipal Water Used (gallons per year) 197,960

Total Rainwater Spilled (gallons per year) 0

Figure 6. Scenario C: Results

63

Lan

dsca

pe &

Fou

ntai

n W

ater

Dem

ands

onl

y, e

xist

ing

pow

er p

lant

& p

ropo

sed

offic

e ro

of a

rea

Mon

th

Out

door

Wat

er

Dem

and

(Gal

lons

) To

tal

Dem

ands

(G

allo

ns)

Tota

l D

eman

d M

et b

y R

ainw

ater

(G

allo

ns)

Med

ian

Rai

nfal

l (In

ches

)

Rai

nfal

l C

olle

cted

(G

allo

ns)

Rai

nwat

er

Spill

ed

(gal

lons

)

End-

of-M

onth

St

orag

e

(250

00 g

al. t

o st

art)

Mun

icip

al

Rai

nwat

er

Use

d (G

allo

ns)

Fo

unta

in

Land

scap

e

25,0

00

Jan

6,32

6 11

,837

18

,163

14

,857

1.

44

53,0

10

63

,153

3,

306

Feb

5,75

1 16

,065

21

,815

17

,845

1.

90

69,9

44

11

5,25

3 3,

970

Mar

19

,839

56

,438

76

,277

62

,395

1.

63

60,0

05

11

2,86

3 13

,882

Apr

22,4

27

67,8

52

90,2

79

73,8

48

2.06

75

,834

114,

849

16,4

31

May

13

,514

92

,161

10

5,67

4 86

,442

3.

19

117,

433

14

5,84

0 19

,233

Jun

35,8

45

125,

135

160,

980

131,

682

2.36

86

,878

101,

036

29,2

98

Jul

59,7

10

144,

794

204,

503

167,

284

1.27

46

,752

-19,

496

37,2

20

Aug

50,8

92

139,

720

190,

613

155,

921

1.59

58

,532

-116

,885

34

,692

Sep

23,7

69

71,8

68

95,6

37

78,2

31

2.82

10

3,81

2

-91,

304

17,4

06

Oct

18

,593

52

,210

70

,804

57

,917

2.

46

90,5

59

-5

8,66

2 12

,886

Nov

13

,035

30

,438

43

,473

35

,561

1.

64

60,3

73

-3

3,85

0 7,

912

Dec

3,

738

5,70

7 9,

445

7,72

6 1.

81

66,6

31

25

,055

1,

719

SUM

S 27

3,43

8 81

4,22

6 1,

087,

664

889,

709

24.1

7

889,

764

0

197,

955

Figu

re 7

. Sc

enar

io C

: Wat

er D

eman

d M

odel

64

Scenario D: Irrigation, fountains, toilets with 100,000 gallons additional storage

This scenario evaluated the outdoor and the indoor water demands when

compared with the rainwater that could be collected from the both the existing Seaholm

Power Plant and the proposed office building. Scenario D would require the most

additional equipment and maintenance. The use of the rainwater to supplement the

demands for indoor water greatly increases the amount of required plumbing, which

inherently affects the cost of parts and labor. Storage capacity would need to expand to

approximately 100,000 gallons. It was found that the additional demands greatly reduced

the percentage of the system to meet its supply expectations between 36% (thirty-six) and

37% (thirty-seven). The demands exceeded the amount of water stored and captured

between August and October, thus requiring the additional use of municipal water, Figure

8.

Variable Notes Value

Total Rooftop Collection Area (s.f.) Power plant & office roofs 65,660

Total Cistern Capacity (gallons) Existing cistern + 100,000 gallons extra storage 107,000

Water Demands Evaluated (gallons) Landscape irrigation and fountain only 2,460,540

Percentage of Demands Met with Rainwater

In order to meet optimum system flow 36.1%

Total Rainwater Harvested (gallons per year) 888,260

Total Municipal Water Used (gallons per year) 1,572,290

Total Rainwater Spilled (gallons per year) 0

Figure 8. Scenario D: Results

65

Out

door

and

indo

or w

ater

dem

ands

, exi

stin

g po

wer

pla

nt &

pro

pose

d of

fice

roof

are

a M

onth

In

door

Wat

er

dem

and

(G

allo

ns)

Out

door

Wat

er

Dem

and

(Gal

lons

)

Tota

l D

eman

ds

(Gal

lons

)

Tota

l D

eman

d M

et

(Gal

lons

)

Med

ian

Rai

nfal

l (In

ches

)

Rai

nfal

l co

llect

ed

(Gal

lons

)

Rai

nwat

er

Spill

ed

(Gal

lons

)

End-

of-

mon

th

stor

age

(2

5000

gal

. to

star

t)

Mun

icip

al

Rai

nwat

er

Use

d (G

allo

ns)

O

ffice

R

etai

l Fo

unta

in

Land

scap

e

25,0

00

Jan

84,4

80

23,0

68

6,32

6 11

,837

12

5,71

1 45

,382

1.

44

53,0

10

32

,629

80

,329

Feb

84,4

80

20,8

36

5,75

1 16

,065

12

7,13

1 45

,894

1.

90

69,9

44

56

,679

81

,237

Mar

84

,480

23

,068

19

,839

56

,438

18

3,82

5 66

,361

1.

63

60,0

05

50

,323

11

7,46

4

Apr

84,4

80

22,3

24

22,4

27

67,8

52

197,

083

71,1

47

2.06

75

,834

55,0

10

125,

936

May

84

,480

23

,068

13

,514

92

,161

21

3,22

2 76

,973

3.

19

117,

433

95

,469

13

6,24

9

Jun

84,4

80

23,0

68

35,8

45

125,

135

268,

528

96,9

39

2.36

86

,878

85,4

09

171,

590

Jul

84,4

80

22,3

24

59,7

10

144,

794

311,

307

112,

382

1.27

46

,752

19,7

79

198,

925

Aug

84,4

80

23,0

68

50,8

92

139,

720

298,

161

107,

636

1.59

58

,532

-29,

325

190,

525

Sep

84,4

80

22,3

24

23,7

69

139,

720

270,

293

97,5

76

2.82

10

3,81

2

-23,

089

172,

717

Oct

84

,480

23

,068

18

,593

71

,868

19

8,01

0 71

,482

2.

46

90,5

59

-4

,011

12

6,52

8

Nov

84

,480

22

,324

13

,035

30

,438

15

0,27

7 54

,250

1.

64

60,3

73

2,

112

96,0

27

Dec

84

,480

23

,068

3,

738

5,70

7 11

6,99

3 42

,234

1.

81

66,6

31

26

,509

74

,759

SUM

S 1,

013,

760

271,

607

273,

438

901,

736

2,46

0,54

2 88

8,25

6 24

.17

88

9,76

4 0

1,

572,

286

Figu

re 9

. Sc

enar

io D

: W

ater

Dem

and

Mod

el

66

Appendix F: Stormwater Considerations at Seaholm

For site development, the City of Austin Drainage Criteria Manual requires that storm

water flow from a developed site “cannot exceed capacities of the existing downstream

drainage systems, or the predeveloped peak runoff rate of the site, whichever is less.”

Typically the reduction in peak runoff rate is achieved through the construction of a

storm water detention facility. In the case of the Seaholm site, collecting a portion of the

site’s precipitation essentially has the same runoff reduction effect as detention. By

reducing a portion of the site’s runoff volume through rainwater collection, the size and

therefore the cost of the developed site’s detention facility would be less due to the

supplemental rainwater collection.

Due to the large amount of impervious coverage contained in the plaza area, ample

evidence supports the generation of a considerable amount of storm water runoff from the

site. Capturing, storing, and reusing this water for either irrigation purposes either for the

indoor office facility use is imperative in order to mitigate the adverse impacts of the

excessive water that otherwise will be lost to evaporation. Primarily, water collected

from the site would be implemented in agricultural irrigation applications of the

landscape within and around the site. To achieve this, water runoff must be collected

from the plaza area and stored in the fuel tanks adjacent to the site. Traditional curb and

gutter drainage methods could be utilized in the project to divert storm water to storage

tanks (the City of Ann Arbor, Michigan, Website: http://www.ci.ann-arbor.mi.us).

A myriad of methods should be considered for the project to increase the infiltration

of water on site; to allow bio-remediation of pollutants by soils and plants; and to reduce

the storm water flow. Other factors that aid in the improvement of storm water quality are

the reduction of the amount of impervious surface, the collection and on-site storage of

storm water, and the increase in vegetation (the City of Ann Arbor, Michigan, Website:

http://www.ci.ann-arbor.mi.us). To mimic the functions of nature lost to urbanization,

natural options and onsite features can be used such as vegetated swales, as infiltration

67

trenches, and in bioretention. Structural means to hold storm water, such as rain barrels,

and to treat storm water should be considered and should be evaluated.

The integration of water conservation, of recycling, and of storm water collection,

storage and treatment, are all recommended strategies for the site (CABE Associates,

Inc., website: http://www.cabe.com/2000text.shtml) and it is important to generate site

plans for the plaza and the surrounding areas. Plans for the site should show adequate

grading and slopes, directions for the plaza and for the surrounding areas.

68

Appendix G: Radiance Scenarios

Low Consumption Scenario

An annual consumption pattern of houses with low-water demand was derived and

was used for developing models under this scenario. The average monthly water

consumption, aggregated annually, for such houses 2,057 gallons. However, significant

monthly variation was seen in the consumption pattern between summer & non-summer

months. Assuming that this difference was essentially associated with an increase in

outdoor expenditure of water for upkeep of the lawn and other landscape features, a

baseline indoor consumption demand was established based on consumption in the non-

summer months. The baseline indoor consumption level, as seen in Figure 1, was found

to be 1,690 gallons of water per month. Based on this information, an outdoor and an

indoor water demand pattern was established. Outdoor consumption is assumed to be all

values above the baseline value, and indoor consumption values at or below the baseline

level.

For a combined indoor &

outdoor low-water demand

pattern, the rain water system

was found to be effective in

meeting 88% (eighty-eight)

of all water demand, with a

collection area of 1600 sq. ft

(Appendix J). This model

was further tested for

efficiency with a larger

collection roof size; it was determined that with a roof size of 1850 sq. ft. or higher,

100% demand under this scenario was met.

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1 2 3 4 5 6 7 8 9 10 11 12

Series1

Figure 1: Typical annual water consumption for low scenario

69

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

1 2 3 4 5 6 7 8 9 10 11 12

Series1

Figure 2. Typical annual water consumption for average scenario

For low consumption outdoor use only, it was seen that a 100% water demand was

met by the rain water system. Instead, under this scenario the consumption was so low

that there would be a very high amount of overflow and a very large cistern would be

needed to hold the monthly bourgeoning water residual. It was thus deemed that this

scenario was fairly impractical and ultimately infeasible, as displayed in Figure 1.

However, this model was analyzed further to check the proportion of indoor demand that

the model could meet, after meeting a 100% outdoor demand. It was seen that the rain

water system could meet 100% of outdoor demand and 85% (eighty-five) indoor demand

(Appendix J).

For low-consumption indoor use, it was again noted that 100% demand was satisfied

by the rainwater system. In summation, this system was deemed quite effective under the

low consumption scenario. The water demand for the given consumption pattern was met

almost entirely by rainwater alone. It was also concluded that a 6,000 gallon cistern

would suffice to hold the monthly residual generated by the rainwater system for indoor

and outdoor usage or outdoor only usage. An 8,000 gallon cistern is necessary to meet

storage needs for the indoor only scenario.

Average Consumption Scenario

An average annual consumption pattern of all houses within the Radiance subdivision

was calculated and used for

developing models under this

scenario. The average

monthly water consumption,

aggregated annually, for all

houses was observed to be

5,076 gallons. Again, the

significant monthly variation

in water consumption

between summer & non-

70

summer months was used to derive the outdoor & indoor water consumption pattern,

since it was inferred that this differential was essentially associated with an increase in

outdoor expenditure of water for lawn maintenance and for other landscape features. The

baseline indoor consumption level established using non-summer monthly consumption

was found to be 4,331 gallons of water per month. Based on this information, an outdoor

and indoor water demand pattern was established.

For a combined indoor & outdoor average water demand pattern, the rain water

system was found to be effective in meeting 35.5% of all water demand. The collection

area was again assumed to be a roof measuring 1,600 sq. ft. This model too was further

tested for efficiency with a larger collection roof size. It was found that with a roof size of

2,200 sq. ft., 48% of demand under this scenario was met by rainwater alone.

For average consumption outdoor use only, it was again seen that 100% water

demand was met by the rain water system. This model was further improvised to check

the proportion of indoor demand that the model could meet after meeting a 100% outdoor

demand. It was seen that the rain water system could meet a 100% outdoor demand and

23% indoor demand. The highest monthly water residual in the cistern was seen as 7,700

gallons. Hence this particular scenario needs a larger cistern capable of holding about

8,000 gallons of water.

For average consumption indoor use, it was noted that 43% (forty-three) of

demand was satisfied by the rainwater system. Summarizing, the rain water system can

effectively meet a significant portion of the water demand for the given average

consumption pattern. It was also observed that a cistern size of 7,000 gallons would

sufficiently hold the monthly residual generated by the rainwater system in the indoor

and outdoor combined water use scenario. A 5,000 gallon cistern is the appropriate size

cistern to accommodate residual for indoor only usage, while trying to store the residual

rainwater for the outdoor only scenario is unfeasible due to the rate of increasing

residual.

71

High Consumption Scenario

An annual utilization pattern of all high-water consumption houses within the

Radiance subdivision yielded the high water usage pattern used for developing models

under this scenario. The average monthly water consumption, aggregated annually, for

these high consumption houses was observed to be 10,514 gallons. Again, the significant

monthly variation in water consumption between summer & non-summer months was

used to derive the outdoor & indoor water consumption pattern, since, assumptively, this

difference was essentially associated with an outdoor expenditure increase of water for

upkeep of the lawn and for other landscape features. This difference was especially

pronounced in the high-consumption scenario. The baseline indoor consumption level

established using non-summer monthly consumption in this scenario was found to be

7,715 gallons of water per month. Again, based on this information, a high consumption

outdoor and indoor water demand pattern was established.

For the combined

indoor & outdoor high-

water demand pattern, the

rainwater system only

contributed to a mere 17%

(seventeen) of the

cumulative water demand.

The collection area was

again assumed to be a roof

measuring 1,600 sq. ft.

For high-consumption outdoor use only, the rainwater system only met 57% (fifty-

seven) of the total water demand. This indicates the wide disparity in the water

consumption pattern between high-consumption houses and the average Radiance house.

This model also observed a very high water residual in the early summer months. The

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1 2 3 4 5 6 7 8 9 10 11 12

Series1

Figure 3. Typical average annual consumption in high scenario

72

system necessitates an 11,000 gallon cistern, which might make this scenario unfeasible,

see Figure 3.

For high-consumption indoor use pattern, it was noted that 25% (twenty-five) of the

demand was satisfied by the rainwater system. This model was further tested for

efficiency with a larger collection roof size. It was found that with a roof size of 2,200 sq.

ft. 34% (thirty-four) demand under this scenario was met by rainwater alone.

The rainwater system alone does not meet a significant portion of the water demand

for high consumption homes. However, for houses with bigger roof areas, a more

significant portion of the indoor water demand can be met by this system. It was also

observed that a cistern size of 6,000 gallons would sufficiently hold the monthly residual

generated by the rainwater system in the indoor water use scenario. The combined indoor

& outdoor water use would need approximately 8,000 gallons of capacity to hold the

necessary amount of water.

73

Appendix H: Radiance Systems Modeling

The following nine tables were generated using spreadsheet modeling to evaluate

three different levels of water consumption and three different modes of usage.

Assuming a pre-determined roof size, the consumption matrix yields nine different

combinations of rainwater and municipal water supply, offering a quantitative method to

determine both the practical and the economic feasibility of a rainwater system. In the

nine iterations that follow, the only variables that not fixed are the level of consumption

and the water usage pattern, whether inside, outside or both. Fixed variables include the

efficiency of the system, the size of the roof and the average amount of rainfall.

However, by changing the fixed and non-fixed variables, it becomes possible to use these

models to answer many of questions surrounding the implementation of a rainwater

system: roof size, necessary rainfall, etc.

1. Low Consumption

2. Average Consumption

3. High Consumption

A. Indoor & Outdoor Model 1A Model 2A Model 3A

B. Outdoor Only Model 1B Model 2B Model 3B

C. Indoor Only Model 1C Model 2C Model 3C

Figure 1. Consumption - Usage Matrix

74

Low Water Consumption:

Rainfall Collection - 90% collection, Low Demand, Indoor and Outdoor Usage

Month

Low Water demand

(indoor and outdoor)

Water demand from rainfall

(Indoor & outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0.12

Jan 2,056 1809.13 1.44 1291.85 4482.72 4444.66 4406.60

Feb 1,085 954.60 1.90 1704.53 5232.65 5194.59 5156.53

Mar 1,643 1445.99 1.63 1462.31 5248.97 5210.91 5172.85

Roof catchment area ,sq. ft.

1600

Apr 2,434 2142.14 2.06 1848.07 4954.90 4916.84 4878.78

May 3,186 2803.68 3.19 2861.81 5013.03 4974.97 4936.91

Jun 2,147 1889.21 2.36 2117.20 5241.02 5202.96 5164.90

Collection coefficent, gal/sq.ft/in.

0.623

Jul 2,213 1947.15 1.27 1139.34 4433.21 4395.15 4357.10

Aug 2,879 2533.23 1.59 1426.42 3326.41 3288.35 3250.29

Initial water stored, gal 5000

Sep 1,871 1646.48 2.82 2529.88 4209.81 4171.75 4133.69 Oct 1,906 1677.28 2.46 2206.92 4739.44 4701.38 4663.32 Nov 1,317 1158.96 1.64 1471.28 5051.76 5013.70 4975.64 Dec 1,947 1713.60 1.81 1623.79 4961.94 4923.88 4885.82

SUM 21721.45 24.17 21683.39

Figure 2. Model 1A

Rainfall Collection - 90% collection, Low Demand, Outdoor Usage Only

Month

Low Water demand

(outdoor)

Water demand from

rainfall (outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0

Jan 1802.44 1802.44 1.44 1291.85 4489.41 4376.62 4263.84

Feb 922.06 922.06 1.90 1704.53 5271.89 5159.10 5046.31

Mar 1396.69 1396.69 1.63 1462.31 5337.50 5224.71 5111.92

Roof catchment area ,sq. ft.

1600

Apr 2180.86 2180.86 2.06 1848.07 5004.71 4891.92 4779.13

May 2932.61 2932.61 3.19 2861.81 4933.92 4821.13 4708.34

Jun 1893.44 1893.44 2.36 2117.20 5157.68 5044.89 4932.10

Collection coefficent, gal/sq.ft/in.

0.623

Jul 1959.27 1959.27 1.27 1139.34 4337.75 4224.96 4112.17

Aug 2625.27 2625.27 1.59 1426.42 3138.90 3026.11 2913.32

Initial water stored, gal 5000

Sep 1617.61 1617.61 2.82 2529.88 4051.17 3938.38 3825.59 Oct 1652.61 1652.61 2.46 2206.92 4605.48 4492.69 4379.90 Nov 1119.45 1119.45 1.64 1471.28 4957.31 4844.52 4731.73 Dec 1693.88 1693.88 1.81 1623.79 4887.21 4774.42 4661.63

SUM 21796.18 24.17 21683.39

Figure 3. Model 1B

75

Low Water Consumption (cont.):

Rainfall Collection - 90% collection, Low Demand, Indoor Usage Only

Month

Low Water demand (indoor)

Water demand from

rainfall (Indoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0

Jan 1,689.29 1689.29 1.44 1291.85 102.56 2537.38 4972.20

Feb 1,084.77 1084.77 1.90 1704.53 722.32 3157.14 5591.96

Mar 1,643.17 1643.17 1.63 1462.31 541.46 2976.28 5411.09

Roof catchment area ,sq. ft.

1600

Apr 1,689.29 1689.29 2.06 1848.07 700.23 3135.05 5569.87

May 1,689.29 1689.29 3.19 2861.81 1872.75 4307.57 6742.39

Jun 1,689.29 1689.29 2.36 2117.20 2300.66 4735.48 7170.30

Collection coefficent, gal/sq.ft/in.

0.623

Jul 1,689.29 1689.29 1.27 1139.34 1750.71 4185.53 6620.35

Aug 1,689.29 1689.29 1.59 1426.42 1487.84 3922.66 6357.48

Initial water stored, gal 500

Sep 1,689.29 1689.29 2.82 2529.88 2328.43 4763.24 7198.06 Oct 1,689.29 1689.29 2.46 2206.92 2846.05 5280.87 7715.69 Nov 1,317.00 1317.00 1.64 1471.28 3000.32 5435.14 7869.96 Dec 1,689.29 1689.29 1.81 1623.79 2934.82 5369.64 7804.46

SUM 19248.57 24.17 21683.39

Figure 4. Model 1C

Average Water Consumption:

Rainfall Collection - 90% collection, Average Demand, Indoor and Outdoor Usage

Month

Water demand (indoor

and outdoor)

Water demand

from rainfall (Indoor & outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0.645

Jan 4,181 1484.26 1.44 1291.85 4807.60 4866.52 4925.44

Feb 3,631 1289.01 1.90 1704.53 5223.12 5282.04 5340.96

Mar 4,346 1542.83 1.63 1462.31 5142.60 5201.52 5260.44

Roof catchment area ,sq. ft.

1600

Apr 4,924 1748.02 2.06 1848.07 5242.64 5301.56 5360.48

May 5,461 1938.66 3.19 2861.81 6165.80 6224.72 6283.64

Jun 5,639 2001.85 2.36 2117.20 6281.16 6340.08 6399.00

Collection coefficent, gal/sq.ft/in.

0.623

Jul 6,531 2318.51 1.27 1139.34 5102.00 5160.92 5219.84

Aug 7,211 2559.91 1.59 1426.42 3968.51 4027.43 4086.35

Initial water stored, gal 5000

Sep 5,753 2042.32 2.82 2529.88 4456.08 4515.00 4573.92 Oct 4,815 1709.33 2.46 2206.92 4953.67 5012.59 5071.51 Nov 4,218 1497.39 1.64 1471.28 4927.55 4986.47 5045.39 Dec 4,204 1492.42 1.81 1623.79 5058.92 5117.84 5176.76

SUM 21624.47 24.17 21683.39

Figure 5. Model 2A

76

Average Water Consumption (cont.):

Rainfall Collection - 90% collection, Average Demand, Outdoor Usage Only

Month

Water demand

(outdoor)

Water demand

from rainfall (outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0

Jan 0 0.00 1.44 1291.85 3291.85 4915.64 16569.35

Feb 0 0.00 1.90 1704.53 3704.53 6620.17 18273.88

Mar 15 14.71 1.63 1462.31 3447.60 8067.76 19721.47

Roof catchment area ,sq. ft.

1600

Apr 593 592.71 2.06 1848.07 3255.36 9323.12 20976.83

May 1,130 1129.71 3.19 2861.81 3732.10 11055.22 22708.93

Jun 1,308 1307.71 2.36 2117.20 2809.49 11864.72 23518.43

Collection coefficent, gal/sq.ft/in.

0.623

Jul 2,200 2199.71 1.27 1139.34 939.63 10804.35 22458.06

Aug 2,880 2879.71 1.59 1426.42 546.71 9351.06 21004.77

Initial water stored, gal 2000

Sep 1,422 1421.71 2.82 2529.88 3108.17 10459.23 22112.94 Oct 484 483.71 2.46 2206.92 3723.21 12182.43 23836.14 Nov 0 0.00 1.64 1471.28 3471.28 13653.71 25307.42 Dec 0 0.00 1.81 1623.79 3623.79 15277.50 26931.21

SUM 10029.68 24.17 21683.39

Figure 6. Model 2B

Rainfall Collection - 90% collection, Average Demand, Indoor Usage Only

Month

Average Water

demand (indoor)

Water demand

from rainfall (Indoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0.57

Jan 4,181.00 1797.83 1.44 1291.85 3994.02 3797.16 3600.29 Feb 3,631.00 1561.33 1.90 1704.53 4137.22 3940.35 3743.49 Mar 4,331.29 1862.45 1.63 1462.31 3737.07 3540.20 3343.34

Roof catchment area ,sq. ft.

1600

Apr 4,331.29 1862.45 2.06 1848.07 3722.68 3525.82 3328.95 May 4,331.29 1862.45 3.19 2861.81 4722.04 4525.18 4328.31 Jun 4,331.29 1862.45 2.36 2117.20 4976.79 4779.92 4583.06

Collection coefficent, gal/sq.ft/in.

0.623

Jul 4,331.29 1862.45 1.27 1139.34 4253.68 4056.81 3859.94 Aug 4,331.29 1862.45 1.59 1426.42 3817.64 3620.78 3423.91

Initial water stored, gal 4500

Sep 4,331.29 1862.45 2.82 2529.88 4485.07 4288.20 4091.33 Oct 4,331.29 1862.45 2.46 2206.92 4829.53 4632.66 4435.79 Nov 4,218.00 1813.74 1.64 1471.28 4487.07 4290.20 4093.33 Dec 4,204.00 1807.72 1.81 1623.79 4303.13 4106.27 3909.40

SUM 21880.26 24.17 21683.39

Figure 7. Model 2C

77

High Water Consumption:

Rainfall Collection - 90% collection, High Demand, Indoor and Outdoor Usage

Month

High Water demand

(indoor and outdoor)

Water demand from

rainfall (Indoor & outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0.83

Jan 6,426.42 1092.49 1.44 1291.85 5199.36 5434.95 5670.55

Feb 5,982.33 1017.00 1.90 1704.53 5886.89 6122.49 6358.08

Mar 7,326.67 1245.53 1.63 1462.31 6103.67 6339.26 6574.85

Roof catchment area ,sq. ft.

1600

Apr 9,769.67 1660.84 2.06 1848.07 6290.89 6526.48 6762.07

May 11,649.67 1980.44 3.19 2861.81 7172.26 7407.85 7643.44

Jun 13,175.00 2239.75 2.36 2117.20 7049.71 7285.30 7520.90

Collection coefficent, gal/sq.ft/in.

0.623

Jul 16,391.00 2786.47 1.27 1139.34 5402.58 5638.18 5873.77

Aug 17,901.00 3043.17 1.59 1426.42 3785.84 4021.43 4257.02

Initial water stored, gal 5000

Sep 13,039.37 2216.69 2.82 2529.88 4099.02 4334.61 4570.21 Oct 9,958.40 1692.93 2.46 2206.92 4613.01 4848.60 5084.19 Nov 7,967.20 1354.42 1.64 1471.28 4729.86 4965.45 5201.05 Dec 6,576.80 1118.06 1.81 1623.79 5235.59 5471.19 5706.78

SUM 21447.80 24.17 21683.39

Figure 8. Model 1C

Rainfall Collection - 90% collection, High Demand, Outdoor Usage Only

Month

High Water demand

(outdoor)

Water demand from

rainfall (outdoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by

municipal 0.43

Jan 0.00 0.00 1.44 1291.85 6291.85 6242.02 6192.19

Feb 0.00 0.00 1.90 1704.53 7996.38 7946.55 7896.72

Mar 0.00 0.00 1.63 1462.31 9458.69 9408.85 9359.02

Roof catchment area ,sq. ft.

1600

Apr 2,054.31 1170.96 2.06 1848.07 10135.80 10085.96 10036.13

May 3,934.31 2242.56 3.19 2861.81 10755.05 10705.22 10655.39

Jun 5,459.65 3112.00 2.36 2117.20 9760.26 9710.42 9660.59

Collection coefficent, gal/sq.ft/in.

0.623

Jul 8,675.65 4945.12 1.27 1139.34 5954.48 5904.65 5854.82

Aug 10,185.65 5805.82 1.59 1426.42 1575.08 1525.25 1475.42

Initial water stored, gal 5000

Sep 5,324.01 3034.69 2.82 2529.88 1070.28 1020.44 970.61 Oct 2,243.05 1278.54 2.46 2206.92 1998.65 1948.82 1898.99 Nov 251.85 143.55 1.64 1471.28 3326.38 3276.55 3226.71 Dec 0.00 0.00 1.81 1623.79 4950.17 4900.33 4850.50

SUM 21733.22 24.17 21683.39

Figure 9. Model 2C

78

High Water Consumption (con’t):

Rainfall Collection - 90% collection, High Demand, Indoor Usage Only

Month

High Water demand (indoor)

Water demand from

rainfall (Indoor)

Median Rainfall,

in.

Rainfall collected,

gal.

End-of-month

storage (Year 1)

End-of-month

storage (Year 2)

End-of-month

storage (Year 3)

% supplied by municipal 0.75

Jan 6,426.42 1606.60 1.44 1291.85 4685.25 4359.88 4034.50

Feb 5,982.33 1495.58 1.90 1704.53 4894.19 4568.82 4243.45

Mar 7,326.67 1831.67 1.63 1462.31 4524.83 4199.46 3874.09

Roof catchment area ,sq. ft.

1600

Apr 7,715.35 1928.84 2.06 1848.07 4444.06 4118.69 3793.31

May 7,715.35 1928.84 3.19 2861.81 5377.03 5051.66 4726.29

Jun 7,715.35 1928.84 2.36 2117.20 5565.40 5240.03 4914.65

Collection coefficent, gal/sq.ft/in.

0.623

Jul 7,715.35 1928.84 1.27 1139.34 4775.90 4450.53 4125.16

Aug 7,715.35 1928.84 1.59 1426.42 4273.49 3948.11 3622.74

Initial water stored, gal 5000

Sep 7,715.35 1928.84 2.82 2529.88 4874.52 4549.15 4223.78 Oct 7,715.35 1928.84 2.46 2206.92 5152.60 4827.23 4501.85 Nov 7,715.35 1928.84 1.64 1471.28 4695.04 4369.67 4044.29 Dec 6,576.80 1644.20 1.81 1623.79 4674.63 4349.25 4023.88

SUM 22008.76 24.17 21683.39

Figure 10. Model 3C

79

Appendix I: Economic Analysis

Implementation of Individual Rainwater Harvesting System

This section will provide all of the figures that were created to analyze the cost of

implementing rainwater collection systems on individual systems. Please see the

description in the report for background information on the boundaries of this analysis.

Figures 1 thru 9 show the economic feasibility of the nine permutations of rainwater

system uses, of users and of roof size.

Cost Analysis: Low Consumption, Indoor & Outdoor

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 1. Cost Analysis of Low Consumption Household for Indoor and Outdoor Use

80

Cost Analysis: Low Consumption, Outdoor Only

$-

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

$12,000.00

$14,000.00

$16,000.00

$18,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 2. Cost Analysis of Low Consumption Household for Outdoor Use

Cost Analysis: Low Consumption, Indoor & Outdoor, Large Roof

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 3. Cost Analysis of Low Consumption Household for Indoor and Outdoor Use with Large Roof

81

Cost Analysis: Medium Consumption, Indoor & Outdoor

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 4. Cost Analysis of Medium Consumption Household for Indoor and Outdoor Use

Cost Analysis: Medium Consumption, Outdoor Only

$-

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

$12,000.00

$14,000.00

$16,000.00

$18,000.00

$20,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 5. Cost Analysis of Medium Consumption Household Outdoor Use

82

Cost Analysis: Medium Consumption, Indoor & Outdoor, Large Roof

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 6. Cost Analysis of Medium Consumption Household for Indoor and Outdoor Use with Large Roof

Cost Analysis: High Consumption, Indoor & Outdoor

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 7. Cost Analysis of High Consumption Household for Indoor and Outdoor Use

83

Cost Analysis: High Consumption, Outdoor Only

$-

$2,000.00

$4,000.00

$6,000.00

$8,000.00

$10,000.00

$12,000.00

$14,000.00

$16,000.00

$18,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 8. Cost Analysis of High Consumption Household Outdoor Use

Cost Analysis: High Consumption, Indoor & Outdoor, Large Roof

$-

$5,000.00

$10,000.00

$15,000.00

$20,000.00

$25,000.00

$30,000.00

$35,000.00

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.)

Cum

ulat

ive

Cos

t ($)

Costs

Savings

Figure 9. Cost Analysis of High Consumption Household for Indoor and Outdoor Use with Large Roof

84

Appendix J: Notes on Cost Analysis and Cisterns

The costs of the various pieces of equipment needed for residential rainwater

collection were obtained from several websites. Tank Town, a major local supplier of

rainwater collection equipment has a catalog listing prices and descriptions for the

various types of equipment they sell for installing rainwater collection systems

(http://rainwater.org/catalog.pdf). Their catalog was used as the main source for pricing

with verification and supplemental information, especially for different types of storage

tanks, found in The Texas Manual on Rainwater Harvesting and the RS Means 2005

Building Construction Cost Data guidebook. As a slight offset to the cost of the

rainwater collection system, Hays County offers a $100 rebate for rainwater collection

systems as well as property tax exemption on the value of the system. The rebate has

already been included in the economic model.

The major expense of a

rainwater collection system is the

storage tank. The size of the storage

tank determines the reliability of the

collection system as a source of water

between rainfall events. The size of

the tank also has a very significant

impact on the cost of the system and

therefore its economic feasibility when

compared to municipal water supply.

The tables shown below summarize

the cost of various types and sizes of

storage tanks, which can then be used

as an input to the economic model to

compare how various storage tank

options affect the cost and economic

feasibility of the system.

Figure 1. Fiberglass Tank Costs. Source: Tank Town2004 Catalog (http://rainwater.org/catalog.pdf)

85

Figure 3: Estimated Tank Costs

Figure 2. Cisterns

86

Appendix K: Cost Analysis and Monthly Savings

Below are three sets of examples of the models designed to quantitatively analyze

various design scenarios considered for the residential developments in the Radiance

Community. These tables and their underlying models resulted in the graphs examined in

Appendix I. These models can be have been designed to allow rainwater systems to be

evaluated for any combination of variables and are available from the University of

Texas.

Low Consumption Square Feet 1600 Ave. monthly water bill savings $ 9.05 Installation Factor 15% Replacement Replacement

Item Cost/Unit Total Intervals (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 1. Monthly Savings

Low Consumption (6000 gal.) Outdoor Only Indoor & Outdoor Large Roof Roof washer $ 850.00 $ 850.00 Tank $ 4,290.00 $ 4,290.00 Pump $ 585.00 $ 585.00 Filter assembly $ 325.00 3 & 5 micron filter* $ 100.00 UV light $ 675.00 Total Cost $ 5,725.00 $ 6,825.00 same Total water consumption 2057 2057 2057 Rainwater consumption 367 1810 2057 Well water consumption 1690 247 0 $ 1.84 $ 9.05 $ 10.29 $ 22.00 Total Monthly Savings $ 1.84 $ 9.05 $ 32.29

Figure 2. System Cost

87

Medium Consumption Square Feet 1600 Ave. monthly water bill savings $ 10.82 Installation Factor 15% Replacement Replacement

Item Cost/Unit Total Intervals (years) Cost Roof washer $ 850.00 $ 850.00 50 N/A Tank (20,000g) $ 4,685.00 $ 4,685.00 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 $ 51.10 N/A N/A * 1 year is a pack (12) 5 micrion filters and (4) 3 micron filters

Figure 3. Monthly Savings

Med Consumption (8000 gal.) Outdoor Only Indoor & Outdoor Large Roof Roof washer $ 850.00 $ 850.00 Tank $ 4,685.00 $ 4,685.00 Pump $ 585.00 $ 585.00 Filter assembly $ 325.00 3 & 5 micron filter* $ 100.00 UV light $ 675.00 Total Cost $ 6,120.00 $ 7,220.00 same Total water consumption 5076 5076 5076 Rainwater consumption 745 1802 2436 Well water consumption 4331 3274 2640 $ 4.47 $ 10.82 $ 14.26 Total Monthly Savings $ 4.47 $ 10.82 $ 14.26

Figure 4. System Cost

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High Consumption Square Feet 1600 Ave. monthly water bill savings $ 12.51 Installation Factor 15% Replacement Replacement

Item Cost/Unit Total Intervals (years) Cost Roof washer $ 850.00 $ 850.00 50 $ 850.00 Tank (20,000g) $ 5,625.00 $ 5,625.00 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 $ 76.65 N/A N/A* 1 year is a pack (12) 5 micrion filters and (4) 3 micron filters

Figure 5. Monthly Savings

High Consumption (11,000 gal.) Outdoor Only Indoor & Outdoor Large Roof Roof washer $ 850.00 $ 850.00 Tank $ 5,625.00 $ 5,625.00 Pump $ 585.00 $ 585.00 Filter assembly $ 325.00 3 & 5 micron filter* $ 100.00 UV light $ 675.00 Total Cost $ 7,060.00 $ 8,160.00 same Total water consumption 10514 10514 10514Rainwater consumption 1595 1787 2623Well water consumption 8919 8727 7891 $ 11.17 $ 12.51 $ 18.36 Total Monthly Savings $ 11.17 $ 12.51 $ 18.36

Figure 6. System Cost

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Appendix L: Seaholm Cost Analysis

To complement the demand models in Appendix D, additional spreadsheet

models were created to allow for variations in the cost of the systems. The models

presented below illustrate the same four scenarios and can be used in conjunction with

the Seaholm demand Models to create a complete picture of the costs associated with

rainwater harvesting.

• 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

Scenario A - Existing System, Additional Storage Add. Stor Vol (Gal) 30,000 Replacement Total

Item Cost/Unit Total Intervals (years) Cost Tank $ 12,000.00 2 50 $ 24,000.00 Filtration System $ 1,000.00 1 50 $ 1,000.00 Pump $ 1,000.00 2 8 $ 2,000.00 Connection* $ 1,000.00 1 $ 1,000.00 Piping $ 8.45 200 25 $ 1,690.00 Maintenance $ 50.00 12 50 $ 600.00 *to municipal water service + bkflw prev, etc Rainwater Collected 476.3 Water Rate $ 3.50 Yearly Savings $ 1,667.05

Figure 1. Scenario A: Cost Analysis

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Scenario B - Additional Storage, Office Bldg Collection Add. Stor Vol (Gal) 60,000 Replacement Total

Item Cost/Unit Total Intervals (years) Cost Tank $ 16,500.00 3 50 $ 49,500.00 Filtration System $ 1,000.00 2 50 $ 2,000.00 Pump $ 1,000.00 3 8 $ 3,000.00 Connection* $ 1,000.00 1 50 $ 1,000.00 Piping $ 8.45 400 25 $ 3,380.00 Maintenance $ 50.00 12 50 $ 600.00 *to municipal water service + bkflw prev, etc Rainwater Collected 814.2 Water Rate $ 3.50 Yearly Savings $ 2,849.70

Figure 2. Scenario B: Cost Analysis

Scenario C - Irrigation + Fountains Add. Stor Vol (Gal) 100,000 Replacement Total

Item Cost/Unit Total Intervals (years) Cost Tank $ 16,500.00 5 50 $ 82,500.00 Filtration System $ 1,000.00 2 50 $ 2,000.00 Pump $ 750.00 4 8 $ 3,000.00 Connection* $ 1,000.00 1 50 $ 1,000.00 Exterior Piping $ 8.45 600 25 $ 5,070.00 Maintenance $ 50.00 12 50 $ 600.00 *to municipal water service + bkflw prev, etc Rainwater Collected 889.7 Water Rate $ 3.50 Yearly Savings $ 3,113.95

Figure 3. Scenario C: Cost Analysis

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Scenario D - Irrigation + Fountains + Flushing Add. Stor Vol (Gal) 100,000 Office Building Size (sf) 100,000 Replacement Total

Item Cost/Unit Total Intervals (years) Cost Tank $ 16,500.00 5 50 $ 82,500.00 Filtration System $ 1,000.00 2 50 $ 2,000.00 Pump $ 1,000.00 6 8 $ 6,000.00 Connection* $ 1,000.00 1 50 $ 1,000.00 Exterior Piping $ 8.45 600 25 $ 5,070.00 Interior Piping $ 0.06 100000 50 $ 6,000.00 Maintenance $ 80.00 12 50 $ 960.00 *to municipal water service + bkflw prev, etc Rainwater Collected 889.7 Water Rate $ 3.50 Yearly Savings $ 3,113.95

Figure 4. Scenario D: Cost Analysis

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