Texas; Rainwater Harvesting Systems For Residential And Commercial Systems

1,023 views

Published on

Texas; Rainwater Harvesting Systems For Residential And Commercial Systems

Published in: Design, Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,023
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
18
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Texas; Rainwater Harvesting Systems For Residential And Commercial Systems

  1. 1. Rainwater Harvesting Systems for Residential and Commercial Systems: Seaholm Power Plant and Radiance Community Community and Regional Planning Program University of Texas School of Architecture Austin, Texas
  2. 2. Urban Environmental Analysis CRP 383: Fall 2005 Professor: Kent ButlerAnalysis Prepared and Presented By: Jason Fryer Additional Research: Ahmed Abukhater Ashley Francis Kyle Irons Andrew Judd Wonsoo Lee Nathan Meade Vipin Nambiar Mary-Elaine SotosCommunity and Regional Planning Program University of Texas School of Architecture Austin, Texas July, 2006
  3. 3. Urban Environmental Analysis CRP 383: Fall 2005 Acknowledgements We would like to thank the following: Seaholm Power Plant Development: John Rosato Southwest Strategies Group Radiance Community Development: Roger Kew Radiance Water Supply Corp. Proofreading: Christa ArnoldCommunity and Regional Planning Program University of Texas School of Architecture Austin, Texas July, 2006
  4. 4. Table of ContentsIntegrated Water Resource Management Integrated Water Resource Management 01 Rainwater Harvesting 05 Storm Water Management 10Seaholm Power Plant Seaholm Power Plant 13 Water Demand Modeling 16 Economic Analysis 21 Recommendations 25Radiance Community Radiance Community 27 Water Demand Modeling 31 Economic Analysis 36 Recommendations 43Appendices Ap pen di x A : S afe ty Co de s 44 Appendix B: Health C odes 51 Appendix C: Seaholm Site 53 Appendix D: Texas Water Related Data 55 Appendix E: Seaholm Demand Model 58 Appendix F: Stormwater Considerations at Seaholm 67 Appendix G: Radiance Scenarios 69 Appendix H: Radiance Modeling 74 Appendix I: Radiance Economic Analysis 80 Appendix J: Notes on Cost Analysis and Cisterns 85 Appendix K: Cost Analysis and Monthly Savings 87 Appendix L: Seaholm Cost Analysis 90
  5. 5. Integrated Water Resource ManagementBackground: Integrated Water Resource Management (IWRM) has become a popular concept inthe practice of sustainable design and of resource management, and its sudden prominencehas led many to believe that IWRM is a new concept, created specifically to address currentwater 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 theEgyptians may have practiced Integrated Water Resource Management well before the birthof 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 majorcomponents of Integrated Water Resource Management (Rahaman & Varis, 2005). Whilethe Spanish, in 1926, were perhaps the first officially to adapt IRWM as an organizationalmodel for water management (Embid, 2003), water resource management was adapted still inthe 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 beenrecommended in many cases and numerous examples of these programs began to developglobally in the 1970’s and ‘80’s. However, despite its newfound prevalence, IntegratedResource Water Management did not intrude upon the public awareness until the last tenyears as water management and water cost issues have become increasingly pressing and thecall for Integrated Resource Water Management was finally added to the agenda of severalworld wide environmental conferences.Definition: In 2002, the Technical Advisory Committee of the Global Water Partnership offeredto Johannesburg World Summit the following definition of Integrated Water ResourceManagement: 1
  6. 6. [Integrated Water Resource Management is] a process, which promotes the coordinated development and management of water, land and related resources in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital systems. Rahaman & Varis, 2005This definition was used to set forth the basic goals of Integrated Resource WaterManagement, and at the Johannesburg World Conference it was further suggested that theseprinciples should be applied within the bailiwick of good government and publicparticipation (Johannesburg, 2002). Unfortunately, despite all of the progress made by theconference attendees, the final definition for Integrated Resource Water Managementmanages to omit any concrete instructions for the technical aspects of IRWM, profferinglofty ideals without providing any practical insight into the application of or the developmentof an integrated water system.Technical Aspects: Integrated Water Resource Management has been hailed as a panacea for all theworld’s water problems; it is effective not only against short-term water shortages and costincreases but also against the impending water crises of the future. After the JohannesburgWorld Conference ended, both public and private individuals struggled with the applicationof definition provided by the Technical Advisory Committee into a practical model for waterconservation and usage. In their report on Integrated Water Management for the CentralTexas Hill Country, Kent Butler and Andrew Karnoven suggest using an integrated approachfor water management (2004). Broken down to its basic components, Butler and Karnoven’sintegrated approach consists of the following four concerns that have been further refined bythe Urban Analysis Seminar at the University of Texas: 1. Water Demand: By analyzing water demand data in an integrated management system it becomes possible to influence the water system systemically. The water system infrastructure can be customized to fit the actual usage, thus reducing wasted 2
  7. 7. resources, and, in turn, this demand data can be used to educate the consumer and hopefully to promote water conservation. The interplay of these two variables, system size and actual water consumption, can be eventually mediated to produce a more efficient allocation of water resources. 2. Water Supply: Hand in hand with the emphasis on water demand comes a focus on the water supply itself. As water demand can only be reduced to a certain level, it becomes necessary to balance conservation efforts with an increase in the volume of water available to meet these demands. Rainwater collection, desalination procedures, or wind harvesting each offer viable alternatives to a traditional well or to a municipal water system. 3. Water Reuse and Reclamation: The third aspect of this integrated approach lies in the reclamation of water from wastewater and from sewage. By focusing on water reclamation and on rehabilitation, additional sources of water are created and these procedures further ease the burden placed on the current water supply. 4. Storm Water Management: The final piece of the integrated water systems puzzle is critical concern in modern building situations involving the treatment and the disposition of storm water runoff. Besides being an additional source of usable water, storm water management is also important to prevent surface erosion and to maintain a healthy environment capable of contributing to an Integrated Water Resource Management System.Justifications: The ultimate goal of any Integrated Water resource Management is the effective andthe efficient use of an important and of an increasingly scarce natural resource: water. Toaccomplish this all four issues referenced above must be considered as well as the followingquestions suggested by Butler and Karnoven: 1. How much water is actually used onsite by the new development? 2. What are the options for water supply sources, and what are the tradeoffs? 3
  8. 8. 3. How much sanitary wastewater and storm water runoff is generated on the site, and what are their likely water quality impacts under different control strategies? 4. Can the various water uses and supplies in a new development be better integrated so as to create more efficient, less consumptive water services? 5. What is the economic feasibility of each of the multiple scenarios and their respective water services? 6. More specifically, how feasible are some of the newer practices, such as rainwater harvesting, in terms of technical requirements and user acceptance on a subdivision scale, or an urban development? Butler & Karnoven, 2004The ultimate goal for devising an Integrated Resource Water Management program is toreduce the impact from a given site on the water supply both upstream and downstream. Bycarefully considering all six of the above questions, as well as the four components of thewater system listed previously, it should become possible to achieve at least some modicumof success. 4
  9. 9. Rainwater Harvesting SystemsBackground Much like Integrated Water Resource Management, rainwater harvesting not only hasbegun to enjoy a newfound popularity, but also is a relatively antiquated concept.Archeologists have found physical evidence of rainwater storage cisterns in Israel dating asfar back as 2000 B.C., with written evidence suggesting that the concept of rainwatercollection and storage techniques existed in China circa 4000 B.C. (Texas Water Development Board, 2005). In early twentieth century Texas, rainwater collection systems received extensive usage until municipal water supplies became financially feasible and readily available, causing rainwater systems to wane both in popularity and in frequency (Krishna, 2003). However, in the last several decades, rainwater systems have resurged with Figure 1. Chinese Cisterns for Rainwater Storage increasing frequency, particularly inthe more arid regions of the southwestern United States, where water shortages are rampantand municipal water costs are on the rise. Currently in the United States, approximately100,000 residential rainwater systems have been implemented, including more than 400professionally installed, full-scale water harvesting systems in Central Texas alone. Thisnumber is constantly on the rise, especially in cities such as Austin, Texas, where the city hasespoused a commitment toward sustainability and toward green building, going so far as tooffer incentive programs that have been responsible for the creation of over 6,000 rainwaterbarrels in the city alone (Water Development Board, 2005). 5
  10. 10. Components Rainwater harvesting is based on a very simple concept: collecting falling rain andstoring it for later use. To that end, a rainwater system can be as simple as a barrel set out instorm to collect water fora small garden, or it canbe complex enough tosatisfy the water supplyfor an entire building.Despite the vastdifferences in complexityand design, most domesticrainwater systems aremade up of six maincomponents (WaterDevelopment Board, Figure 2. Residential Rainwater System2005): 1. Catchment system: Many common rainwater systems will use the building’s existing rooftop as a surface to collect the rainwater, although many newer systems will add a pole barn or rain barn as a structure that provides additional surface area to maximize the volume of water harvested. 2. Gutters and downspouts: Most houses already have existing gutters; however, it is often advisable to upgrade these existing gutters when adding a rainwater system. When installing gutters for a rainwater system, care is essential to correctly size the gutters to handle the flow of water from the roof, and if the system is designated for potable water, the gutters should be inspected for lead seams that can contaminate the water supply. 3. Leaf guards: Leaf guards take several different shapes from funnels to baskets and can be made of a myriad of materials, from nylon to stainless steel. Regardless of the specific form, every leaf guard has a similar function: keeping the system clean and 6
  11. 11. maintaining the flow of water from the catchment surface to the storage area. In addition to a leaf guard, many systems also include a first-flush diverter. This system allows the first fraction of a rainfall to wash the rooftop and helps to remove any debris and any detritus present on the roof. 4. Storage tanks: Often referred to as cisterns, the storage tank is one of the central aspects of any rainwater system. All the water collected from the rooftop is first stored in the storage tanks before it is re-implemented for use. As storage tanks get more expensive when their volume increases, the tank size is often the determining and the limiting factor in the capacity of a rainwater system (Appendix J). 5. Delivery system: Once the water is collected in the storage tank, a system is needed to transport the water from the tank to the tap or into the house. While a gravity fed system would be ideal, it is often necessary to add a pressure tank or a pump to increase the water pressure into the house. Water only gains approximately one psi of pressure for every 2.3 feet of vertical drop and most municipal water systems supply between 40 psi and 60 psi to their domestic users; most internal water systems are not designed to operate below this level. Even typical irrigation systems will require between 15 psi to 20 psi to function properly. 6. Filtration system: A filtration system is suggested for all rainwater systems, but it should be mandatory if the system is deigned for potable water. Various systems can be installed, utilizing mechanical, chemical or even ultraviolet systems, and a professional should be consulted before installing any rainwater system that is intended for potable use.General Concerns: In spite of the relative simplicity of implanting a rainwater system, several seriousconcerns must still be addressed. Both the Texas Commission for Environmental Qualityand the Texas Department of Health supply guidelines and regulations concerning the useand treatment of water garnered from a rainwater harvesting system. The largest issuecentral to both of these sets of code involves the end use of the water supply: potable (fit forhuman consumption) or non-potable (not fit for human consumption). 7
  12. 12. • Potable Water: Potable water sources are generally dealt with under TCEQ Title 30 Part 1 Chapter 290 Subchapter D (Appendix A). This code sets forth guidelines and requirements for the treatment of potable water sources. The TCEQ also put forth requirements for the physical design of the system, the most important of which is the need to maintain a separation between municipal water systems and rainwater systems. The need to prevent cross-contamination can be satisfied by the insertion of an air gap between the two systems or the use of a back flow prevention system. • Non-Potable Water: Non-Potable water supplies have fewer requirements on their implementation, but general guidelines are supplied by the Texas Department of Health and can be found in Sections 341.037, 341.038 and 341.039 of the Texas Administrative Code. The majority of the issues involved deal with public safety and the elimination of public nuisances, but these codes should be consulted when installing any type of rainwater harvesting system (Appendix B).The TCEQ also provides a list of guidelines for water safety and for quality, as well as adefinition of public versus private water systems. Many of these issues are only suggestionsuntil the water system reaches a certain size, but the specific guidelines can be found eitherby contacting the TCEQ or by checking their comprehensive website.Benefits: The obvious benefit derived from the use of a rainwater system is of course theavailability of a low cost alternative to the municipal water supply. However, the cost issueonly 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 groundwater or even to municipal water supplies for a host of reasons (Krishna, 2003): 1. Taste and Purity: Users of potable rainwater systems enjoy a higher purity of water and, consequently, a better tasting supply. 8
  13. 13. 2. Soft Water: Rainwater is naturally a soft water and the lack of minerals eliminates the need for a water softener. Additionally, the mineral deficit causes less wear on appliances and on fixtures, lowering maintenance costs. 3. Contaminant Free: In addition to being naturally sodium free, thereby satisfying an increasingly important dietary requirement, rainwater is free of many of the chemicals that are added to municipal water supplies. 4. Natural Quality: Stored rainwater has been shown to be especially effective for irrigation purposes; plants tend to thrive more from this source than from municipal or from treated water.Despite the obvious advantages, rainwater systems are not always viewed as economicallyfeasible. However, in addition to the purity issues qualified above, rainwater systems alsoallow users to reduce the burden on the water supply during peak demand as well asproviding an alternative means to manage storm water runoff. The argument againstrainwater 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 ofrainwater systems. Balancing the palpable costs of installing a rainwater system against allof the intangible benefits it provides is a difficult task; it becomes problematic to place astrict monetary value on the importance of purity and of taste, or on the ability to reduce theravages of storm water runoff. However, this difficulty should not be allowed to discouragethe implementation of rainwater systems and in the future the advantages gained from theiruse should far outweigh the systems’ monetary value. 9
  14. 14. Storm Water ManagementBackground Under the traditional practice of storm water management, rainwater flows from yardsout 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, waterflows quickly and in great volumes to streams and to lakes. Storm water carries sedimentsand pollutants such as chemicals and fertilizers to creeks and rivers, causing thecontamination of potential drinking water and impacting the food chain that supports theindigenous fish population. By keeping as much rainwater as possible in to proximity towhere it falls and by collecting and reusing this water, we can reduce adverse impacts on ourlakes and streams. In the past, the primary concern centered on the removal of storm water runoff as quicklyas 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 bodywas, historically, the first line of defense. A more recent philosophy of storm watermanagement is to address on-site runoff by developing a comprehensive, integratedapproach, which contends with not only water quality but also to volume and to the rate ofrunoff. Consequently, hydrologic problems can be minimized by preserving and bymaintaining 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 ingreater detail. This includes understanding of the existing hydrologic characteristics as wellas 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 generatedfrom the site and therefore the corresponding size of the storage tanks required to 10
  15. 15. accommodate the excess water runoff. Technical studies must be conducted to evaluate theadequacy and the capacity of the infrastructure in both projects. 11
  16. 16. Seaholm Power Plant:Study on the Feasibility of Installing a Rainwater Harvesting System for Irrigation Community and Regional Planning Program University of Texas School of Architecture Austin, Texas December, 2005
  17. 17. Seaholm Power Plant Built between 1950 and 1958, the Seaholm Power plant sits adjacent to Austin’sTown Lake. During its lifetime, it housed five gas turbines and was capable of producingapproximately 100 megawatts of power. By the 1980s, the plant had ceased to produceenergy and was saved only in 1984 when a Historic Resources survey designated theSeaholm Plant as a high priority historic building. Shortly thereafter, the City of Austin’sTown Lake Comprehensive Plan “suggested that the plant be ‘converted into an activitycenter complimentary to the area’ (City of Austin, 2000).” Thirteen years later theRegional/Urban Design Assistance Team agreed with this recommendation and theSeaholm 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 thewater. The site has been reconditionedand following extensive clean upoperations, has been certified as safe forhuman inhabitation and asenvironmentally sound (Novak, 2006).The five large gas turbines have beenremoved from the interior of thebuilding, but much of the originalstructure is still in place. The remainingbuilding consists of two subterraneanfloors and a main floor with sixty-fivefoot ceilings. The overall structuremeasures approximately 110 feet by 235feet and encompasses more than 100,000square feet (Backus, 2005). Despite theindustrial nature of the structure, light Figure 1. Aerial View: Seaholm Power Plantstreams through two flanking rows of 13
  18. 18. clerestory lights near the ceiling to create an open, inviting, and naturally illuminatedspace with potentially vibrant reuse.Renovation Plans: In April 2005, after the environmental cleanup and recovery of the Seaholm siteand approval of the EPA, the City of Austin selected the Seaholm Power, LLCconsortium to facilitate the renovations at the Seaholm Power Plant. Their missionstatement: to “build a dynamic urban center around Seaholm’s Power Plant as part of afinancially 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 AustinCity Limits and the new KLRU studio. The interior of the power plant will also hostcommercial, retail and unprogrammed public spaces, while the exterior of the buildingwill feature a new multi-story office building and a ten-story residential tower (AppendixC). In addition to these new residents, the site will also reflect the City of Austin’scommitment to green building and to sustainability, represented primarily by a rainwatercollection and harvesting system that will optimize the extensive roof area covering theexisting buildings. Specific details of the proposed facility can be found in the ExecutiveSummary 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, TXregion over the past seventy-five years. The median rainfall derived from this data was24.17 inches per year. It is assumed that only 90% (ninety) of the total rainwater iscaught by the rainwater system. The rooftops evaluated in the models consist of theexisting Seaholm Powerplant (approximately 35,000 square feet), and the proposed officebuilding (approximately 30,500 square feet). It must be noted, however, that certainschemes use these rooftops differently. 14
  19. 19. Rainwater Collection: With approximately 65,000 square feet of rooftop surface available for collectionof rainwater, a rainwater system could be devised that would provide non-potable waterfor use on site. This system would provide several different benefits not only for theSeaholm Project, but also for the City of Austin itself. The rainwater collected from theroof could be stored and then used to satisfy the irrigation requirements for the entiredevelopment. Additionally, depending on the design of the rainwater harvesting system,excess water could also be diverted to fountains and to other architectural elements, thusseverely reducing the load on the city municipal water system while also promotingresponsible water use throughout the remainder of the city. A secondary benefit derivedfrom the use of a rainwater system is the ability to control storm water runoff. The largeroof areas combined with extensive swaths of impervious ground cover create a site thatis extremely susceptible to the ravages of storm water runoff, and the site’s proximity toTown Lake further increase the need to address critical storm water concerns (AppendixF). 15
  20. 20. Water Demand Modeling The purpose of modeling the water demands for a commercial rainwatercollection system was the analysis of various different combinations of rooftop collectionareas, rainwater storage needs, and water demands to find the optimal amount ofrainwater to be harvested to supplement the need for municipal water. The SeaholmPower Plant development incorporates a mixture of uses, landscaping, and paving on theexisting site, Figure 2. The model intends to analyze the benefits of a hybrid system that Figure 2. Seaholm Plant Proposed Development 16
  21. 21. meets its demands through different ratios of rainwater and of municipal water. Inaddition to supplementing municipal water, the rainwater system also decreases the loadimposed on the municipal storm water system by capturing much of the rainwater thatwould otherwise be directed into the surrounding storm water system. Most of thescenarios evaluated are mixed systems; that is, those that use a combination of rainwaterand of municipal water to meet their demands for water. The models have been furthersegregated into intended implementations of the collected rainwater as well as the ratiosof rainwater used versus municipal water used. Each of the scenarios was developed inconjunction with an economic analysis to find the required system components andeventually 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 roofarea for every inch of rainfall was used for calculating the total rainwater that could becollected. The coefficient ensures that the model incorporates concerns regarding lossesoccurring from phenomena such as roof surface evaporation and associated with roofwashing, among others. The rainfall data used in the model is the regional median rainfallrate beginning in 1930 and calculated monthly over a seventy-five year period (AppendixD). The comprehensive nature of the data ensures that the model incorporates climaticuncertainties 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 hybridsystem to meet as much of the total demand as possible with rainwater without acquiringlarge surplus or a deficit of water storage at the end of the year. Thus, the tanks weresized in such a way that minimal water was spilled, and the ratio of demands met byrainwater was determined by the comparison of the amount of rainwater collected and thewater demands of each month. Although the “end-of-month storage” fluctuated heavilydue to higher irrigation needs and lower rainwater collection amounts in the hot, aridmonths, the system’s storage level at the end of the year was approximately even withminimal net gain or loss. The rooftops evaluated in the models consist of the existing Seaholm Power Plant(approximately 35,000 square feet), and the proposed office building (approximately 17
  22. 22. 30,500 square feet), Figure 3. Each scenario uses the optimal combination of rooftopcollection areas needed to accrue the desiredamount of rainfall necessary to meet the typicaldemand as determined by earlier analysis.There is existing water storage, approximately57,000 gallons, located in the power plant justsouth of the Seaholm Power Plant, Figure 4.The models revealed that this storage would Figure 3. Rainwater Collection Areasneed to be supplemented, regardless of thecollected water’s expected use, therefore requiring additional rainwater storage tanks.Each scenario requires differing quantities of additional storage ranging from 30,000gallons to 100,000 gallons in order to produce an optimal system. The water demandanalyzed in the models is derived from multiple factors. First, the outdoor water demands consist primarily of the irrigation of more than65,000 square feet of landscaping, and filling decorative fountains that are approximately12,800 square feet, Figure 4. It was assumed that the landscaping area consisted of threemajor water categories of water demand: low, medium, and high water use. It was assumed that 70% (seventy) of the landscaping would be medium water use, 20% (twenty) would be high water use, and 10% (ten) would be low water use. Each of these categories relates to the amount of irrigation required in comparison to the amount of water that is evaporated as a result of climatic factors. The demand for Figure 4. Rainwater Storage Locations 18
  23. 23. the fountains was based on a similar evaporation factor known as “pan evaporation rate”(Appendix D). An additional evapotranspiration factor of 1.2 was used to account for theadditional loss of water as a result of spraying fountains, since the developers describedthem as “decorative.” The greater surface area and the result of the wind on the sprayingwater increases the amount of water lost above that of the pan evaporation rate. It alsowas assumed that the fountain was filled with 25,000 gallons of municipal water prior torunning the system. Second, the indoor water demands required consideration. In this development, itwas 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 proposedoffice building. These values derived from a projected number of visitors and ofemployees per day in each of the facilities. Using the International Building Code, thequantities of occupants per square foot werefound based on the values given for theusable square footages of the pertinentbuildings of the proposed development.After finding the expected number ofoccupants per day in addition to the typicalwater demands of office employees andretail visitors in the Austin area, the totalwater demand for each month was Figure 5. Proposed Landscapingcalculated.Analysis The intent of this model is the exploration of the possibility of a rainwaterharvesting system to be incorporated into the proposed Seaholm Power Plantredevelopment. It was an interest of the developer to explore the rainwater harvestingsystem both for economic and for environmental reasons. The models aim to calculatethe amount of water demand that can be met with various combinations of rainwater 19
  24. 24. harvesting systems when applied to the proposed designs of the site. Therefore, toexamine the varying scales of rainwater collection systems possible for the SeaholmProject, the model includes four design scenarios. While details of each scenario andtheir subsequent evaluations can be found in Appendix E, the four scenarios can besummarized 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 storageResults Each of the scenarios has unique advantages and disadvantages, but two inparticular appear most efficient. Scenarios B and C were able to implement effectivelythe most amount of water in terms of what was collected. Although they both hadincreased rainwater catchment areas from the proposed office building, they were alsoable to use almost the entirety of what was collected due to the lower demands andincreased storage than in Scenario D. Scenario A showed that the Seaholm Power Plantrooftop alone is insufficient to meet all of the landscape irrigation needs, but was ablestill to fulfill over 50% (fifty) of them. The existing storage also was inadequate, sincethe 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 waterdemands 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 only36% (thirty-six), the lowest of the four scenarios. 20
  25. 25. Economic Analysis The economic analysis model for the Seaholm project will compare the costsassociated with the four rainwater collection system scenarios to the cost of watersupplied by the city of Austin. Water price forecasting has indicated probable increasesin municipal water prices so the economic analysis model will include water priceinflation at 0% (zero), 1% (one), 2% (two), and 3% (three) percent, respectively, overinflation itself, which is assumed to be 2% (two). Costs for the majority of the rainwatercollection system components in the Seaholm Project were obtained from the RS Means2005 Building Construction Cost Data guidebook. It should be noted, though, thatbecause the Seaholm Project is a large-scale and complex development project, the costsobtained 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 rainwatercollection system is storage facilities (Appendix J). Additional storage volume clearlycan provide a greater volume of water available for use. Additional water supplied by thesystem exponentially increases the benefit of the rainwater system. However, from aneconomic perspective, storage should only be increased to a volume which can bereliably filled and consumed by the collection and utilization system, otherwise thepotential benefit created through the cost of additional storage cannot be obtained. For the Seaholm project, because of the high aesthetic priority, tanks placed aboveground are not an option. All of the scenarios include additional storage facilities andonly subterranean tanks will be considered in the analysis. Piping is required to connectand to distribute water among the various collection, storage, and usage components.Other required elements are pumping and filtration equipment. There are a large varietyof pumps that have the potential to be used in various design scenarios. The pumpingconfiguration will depend on specific storage elevation and site data and on irrigationequipment pressure requirements. As a consideration towards implementation, systemmaintenance costs were included in addition to the equipment replacement costs. 21
  26. 26. Although it is assumed building maintenance will have the capability to perform themajority of maintenance tasks, an additional $50 monthly charge was included in thesystem 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 costavoided (through the collection of rainwater) of the volume of water which would havebeen supplied by the water utility. Water is supplied to Seaholm from the Austin WaterUtility 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 Seaholmwater rates are $3.38 per 1000 gallons during the off peak season (November 1 throughJune 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 costavoided through rainwater collection.Creating the Financial Model for Economic Analysis To analyze the economic aspects of the Seaholm rainwater collections system, afinancial model was created. The model was designed to allow the user the flexibility toupdate inputs and to study the system costs as well as water savings implications over afifty-year time period. All replacement and maintenance costs are adjusted for inflation,assuming an increase of 2% (two) annually. Water utility pricing was studied byincreasing increments of inflation above the model’s 2% (two) rate by 1% (one)increments. The financial model considers four design scenarios and compares theconstruction, the maintenance, and the replacement costs of those four options with thecost savings generated from the water volume harvested (Appendix L).Results The accuracy of the economic analysis relies on the quality of the input data. Forthe purposes of this study, the inputs have been fixed, based on information obtainedthrough research and through communication with various project representatives. 22
  27. 27. However, the value of the financial model is in the flexibility to refine inputs based on more current research and on a more current understanding of the projects needs and of its planned direction. The Seaholm economic analysis looks at the relation of the estimated total future water cost savings to the estimated total installation and maintenance costs of the rainwater collection system on a yearly basis for each of the four design scenarios. The economic model indicates that all rainwater system design scenarios under every water price inflation factor have payback periods within the fifty-year analysis period. This result suggests that from an economic perspective, almost any scale of rainwater harvesting system at Seaholm will be a viable project. Table 1 summarizes the payback periods for the four design scenarios. As Figure 6 demonstrates, Scenario B has the shortest payback period, with a scaled-down version of the system, represented by Scenario A, having slightly longer payback periods. Scenarios C and D, which expand the rainwater collection to supply other water uses like exterior fountains and like indoor Years to Achieve Return on Investment Water Price Inflation (%) toilets, have longer payback Scenario 2 3 4 5 periods due to the gratuitous A 29 23 20 19 B 27 21 20 18 costs associated with the C 34 29 26 22 additional storage and D 46 36 30 27 conveyance equipmentFigure 6. Payback Periods required to configure the rainwater system to serve those purposes. This result suggests that financially, it is more beneficial to align the rainwater collection system to serve as few purposes as completely as possible, than to partially supply a larger, more diverse number of uses for the water. The payback periods for Scenarios A and B also illustrate that as long as the water price inflation rate is a minimum of one 1% (one) above normal inflation (represented by 3% (three) inflation), the return on investment for the Seaholm rainwater harvesting system will take 23
  28. 28. approximately twenty years to achieve. The minimal one to two year decreases inpayback period shown with each 1% (one) increase in water price inflation rates indicatethat Scenarios A and B are less sensitive to water price inflation and that the return oninvestment will most likely be achieved within a maximum thirty-year time frame underany water pricing scenario that does not involve a decrease in the price of water. For theSeaholm project, Scenario B would yield the greatest economic benefit by providing themost 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 whichcould be attained under Scenario A. 24
  29. 29. RecommendationsManagement Recommendations The Texas Manual for Rainwater Harvesting recommends that county healthdepartment staff and city building code staff be consulted concerning the construction ofthe rainwater harvesting system and subsequent safe, sanitary operations. It is assumedthat the rainwater system installer will contact the necessary parties. To maintain safeand sanitary operations, we recommend that the system and the landscape that it supportsbe maintained by a dedicated landscape management company. It is not necessary thatthey be on site full-time, however. Additionally, it is imperative that the company hiredbe familiar with rainwater collection system, and it would be beneficial to have theirinvolvement from the inception so that they have a thorough understanding of thecomponents, the conveyance systems, and their integration in the landscape.Monitoring Recommendations The water collected at Seaholm will be non-potable but, because the water willinevitably come into contact with humans, we recommend that the levels of certainpathogens in the water be monitored regularly [The Texas Manual for RainwaterHarvesting 2002]. Routine maintenance operations should be conducted to confirm thatthe system is performing properly and efficiently. Additionally, disinfection systemssuch as the automated chlorination system must undergo routine testing to ensure thehighest level of functionality. 25
  30. 30. Radiance Community: Study on the Feasibility of Installing a RainwaterHarvesting System as an Alternative Water Supply Community and Regional Planning Program University of Texas School of Architecture Austin, Texas December, 2005
  31. 31. Radiance Community Located approximately thirty minutes west of downtown Austin, the RadianceCommunity sits within a housing development in the Texas Hill Country. Thecommunity itself is comprised of approximately forty lots and the developers and theinhabitants share a common desire to tread lightly on their environment. With this goalin mind, the Radiance Community contacted the University of Texas in hopes ofdetermining the feasibility of harvesting rainwater in an attempt to eliminate the need formunicipal water services.Integrated Water Resource Management To facilitate the process of completing a feasibility study for the Radiance Community, the board members provided a complete documentation of the water demand for their community, as well as detailed information on the water usage patterns of the individual homes. This data revealed that the Radiance Community’s desire to adopt a rainwater harvesting system was only a small piece of a larger Integrated Water Resource Management Figure 1. Typical Radiance Household Plan. Analyzing the demand and the usagedata from the community, it is clear that many of the households within Radiance arealready involved in conservation efforts and in the regulation of water demand, the firstcomponent of an IWRM. The desire for a rainwater system, coupled with the use ofcommunity wells, clearly embodies the second tenet of an integrated system, while theirexploration of wastewater processing and of reclamation supports the third requirementof water reclamation and reuse. The final piece of an integrated water program, stormwater management, while not specifically discussed, is nevertheless modulated by the use 27
  32. 32. of any rainwater harvesting system, creating a complete picture of Integrated WaterResource Management.Radiance Residential Development With respect to the site design of the project, the main challenge is achievingintegration of specific management devices into the existing landscape. Many designissues must be taken into account, some of which are safety, cost, maintenance, sitesuitability, and appropriateness and multiple use. To reduce the risk of erosion, protectionis necessary at the outlet of all pips and paved channels where the flow velocity exceedsthe permissible velocity of the receiving channel or area. Structurally lined aprons orother 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. Managementpractices that include wet ponds, detention facilities, infiltration facilities, and wastequality basins can be used singly or in a combinative effort. Devisers are channels thatdirect excess water away from areas where it is unwanted and diverts it to areas where itcan be disposed appropriately. Reducing the impervious surface areas, especially parking lots, can also reduce storm water runoff quantities as well as minimizing construction and maintenance costs. As shown in Figure 2, the use of permeable paving is a recommended alternative for low-traffic parking areas, for emergency access roads, and for driveways. The use of natural landscape provides important benefits for water quality and for the habitat itself in addition to its lower costs for installation and for maintenance than those Figure 2. Permeable Pavement of conventional landscaping. 28
  33. 33. Radiance Project A municipal water utility collects, treats, and distributes water to various facilitieswith the equipment, the operation, and the maintenance costs incorporated into the feethat the utility company charges the water users for their volume of water utilized. Withresidential rainwater collection, the various components of the water supply system arelocated on the property of the residence and they are owned, operated, and maintained bythe person who lives there. In the economic analysis we will be disregarding non-monetary motivations for installing rainwater collection such as water resourceconservation and as environmental stewardship and focus solely on a cost comparison ofrainwater 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 accurateFigure 3. Residential Rainwater Harvesting System 29
  34. 34. economic model for the municipal water supply is outside the scope of this analysis andinstead, 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: acapture subsystem, a storage subsystem, and a distribution subsystem (Figure 3). Thecapture subsystem includes the roof, the gutters, and the roof washer/diverter; the storagesubsystem consists of the storage tank, and the distribution system includes a pump andfiltration 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 arepresent whether there is a rainwater collection system or not, and therefore will not beincluded in the economic analysis. Installation and maintenance costs, with the exceptionof part replacement, are not included in the economic analysis either, because they arenegligible in comparison to the costs associated with buying the equipment itselfnecessary for rainwater collection. Because the Radiance project involves convertinghouses from a well water to a rainwater system there could be additional costs anddifficulties associated with installing the rainwater system such as excavation, grading,and plumbing modifications which are difficult to quantify on a broad basis, but shouldbe considered are on a site-specific basis, and subsequently added to the economicanalysis. 30
  35. 35. Water Demand ModelingWater Demand An important consideration in determining the successful transition from municipal orfrom well water to a rainwater system lies within the water usage patterns of theRadiance Community. With their strict adherence to their goal of minimizing the impacton the environment, many households have already adopted water conservation habits.The water demand data for the current Radiance inhabitants reveals that many householdsare 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 andappliances inside their homes, and the irrigation demands of their landscaping has beenreduced by specifically choosing indigenous plants suited to the climate that require lessirrigation (Appendix D). The Radiance subdivision has a varied pattern of water consumption among itsmembers’ houses; thus the design of a rainwater collection system here must account forthe disparate levels of water demand while ascertaining the feasibility of such a systemwithin 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 developedaddressing various combinations of water consumption patterns for indoor and outdoorwater use. These models establish the volume of rainwater that could be capturedeffectively and stored throughout the year to aid in the reduction of the total water supplyrequired from the Radiance Water Supply Corporation. The models, as seen in AppendixG, have been developed with three categories of consumption; low, average, and high,each developed using water consumption data accumulated within the subdivision overthe 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 andhigh scenarios, respectively, have been developed to account for these extreme users. The 31
  36. 36. models have been further segregated into intended categories of use for the collectedrainwater. The ideal scenario uses rainwater to service the combined outdoor and indoorwater demand, but models have also been developed to study the ability of a rainwatersystem to meet specific indoor or outdoor demands. The models also help estimate the appropriate cistern dimensions necessary for anindependent rainwater system. Based on an aggregated monthly waterdemand/consumption pattern acquired from the Radiance Water Supply Corporation, arainwater collection coefficient of 0.623 gallons of water per square foot roof area forevery 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 modelincorporates concerns about losses occurring from phenomena such as roof surface Figure 4. Consumption Scenarios 32
  37. 37. evaporation and with roof washing, among others. The rainfall data used in the model isthe monthly median rainfall rate in the region calculated, beginning in 1930, over aseventy-five year period. The comprehensive nature of the data ensures that the modelincorporates climatic uncertainties that are typically linked to the effective functioning ofa rainwater system (Appendix D). The model also assumes that the average roof size inthe subdivision is around 1600 sq. ft.; a few optimized models were further tested foreffectiveness 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 bediscussed 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 indoorand outdoor usage) adjacent to each other for ease of comparison. Each cell displays apercentage in the upper left-hand corner, which indicates the percentage of demand thatcan be met with rainwater alone. In the lower right-hand corner, a circle with one of threecolor gradations is displayed to facilitate a quick reference of the practicality of a givenscenario combination. The practicality of a scenario is based on a few inter-relatedfactors and as a result of the factors overlapping; some residents may or may notnecessarily agree with the practicality designated. Factors considered are as follows: 1. Demand Satisfied vs. Tank Size/Cost : • How much demand would be met, and would the return be significant enough to render the tank required to contain that amount of water cost effective? 2. Excess Generated vs. Tank Size/Cost Increase: • Will the amount of water collected be excessive to the point of unacceptable spillage? • Will the tank size require significant increase only to contain surplus rainfall accumulated, not necessarily to amass the amount of water needed to meet the demand for water? 3. Ultimate Practicality: 33
  38. 38. • Does a combination of factors 1 and 2 make the scenario seem particularly unappealing? • Does it simply satisfy so little demand that it is unwise to endure the necessary process of installation and its comparably associated cost?With the above stated factors considered, the gradations seen in Figures 4 and 5 indicatean infeasible/very unpractical scenario, a moderately feasible/practical scenario, or a veryfeasible/highly practical scenario. The practicality of a scenario, as seen below the tablesin Figures 4 and 5, increase as the color changes from red to green (left to right – veryunpractical to highly practical).Results Figure 5. Consumption Scenario Results 34
  39. 39. The analysis performed under the above mentioned consumption scenariosconcludes that it might be significantly advantageous for users under the averageconsumption scenario to use a rainwater system for combined indoor/outdoor and forindoor water use. Specific details of this analysis can be found in Appendix G. It isadditionally beneficial for houses with larger roof areas to install these systems as theycan meet up to half of their water needs through these rainwater systems. Under the lowconsumption scenario almost all of the water requirement, both indoor and outdoor, canbe 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 higherwater demand from the previous scenarios. Given the cost of installation of thesesystems, high-consumption houses using rainwater for indoor use was found to be mostfeasible as with a large enough roof size, almost 34% (thirty-four) of indoor water usecould be met with this system. . 35
  40. 40. Radiance Economic Report Rainwater collection is a completely self-contained form of water supply. Unlikemunicipal water utility supply where the cost of water is based on the volume supplied bythe utility company, rainwater collection the water is free and the cost is contained in theprice of the collection system equipment, and the installation of and the maintenance ofthe system itself. An economic analysis of a rainwater collection system is based on theprice of the various systemic components and the replacement costs of the individualparts, which, in turn are dependent on the volume of water to be collected and stored andits determined function (Appendix J). This section analyzes the economic feasibility of a residential system for the Radiancecommunity in Hays County. This project involves a fairly typical residential conversionfrom well water supply to individual rainwater collection for the Radiance houses, withthe potential implementation throughout the entire community to be managed by theexisting Radiance Water Supply Corporation. Costs for the residential rainwatercollection systems are well established and can be obtained from several websites listedin this report. This economic assessment looks at two different scenario groups. The first scenariogroup will analyze the cost of implementing a rainwater collection system in onehousehold and compare this cost with the reduction in water bill from the Radiance WaterSupply Corporation. The second scenario will analyze the cost of implementingrainwater 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 rainwatercollection for the Radiance project. The model was designed to allow the user the 36
  41. 41. flexibility to update inputs and study the implications over a fifty-year time period. Allcosts are inflation-adjusted assuming a rate of 2% (two) annually. The Radiance project analysis studies the retrofit and the installation of rainwatercollection systems within a residential community for assorted levels of consumption andof uses. This examination determines the financial feasibility of rainwater collectionthrough the comparison of rainwater system lifestyle costs to the combined current waterexpenditures and the supplemental savings accrued by not replacing a well. The modelallows the input of the following variables: the cost of all components of rainwatercollection system, the interval of part replacement, a factor for installation and fortransportation costs as well as the average water bill under a household’s current supply.See Figure 6 for a sample input box for low-consumption household. Low ConsumptionSquare Feet 1600 Ave. monthly savings $ 9.05Installation Factor 15% Replacement Intervals Replacement Item Cost/Unit Total (years) CostRoof washer $ 850.00 $ 850.00 50 N/ATank (10,000g) $ 4,290.00 $ 4,290.00 50 N/APump $ 585.00 $ 585.00 8 $ 585.00Filter assembly $ 325.00 $ 325.00 50 N/A3 & 5 micron filter* $ 100.00 $ 100.00 1 $ 100.00UV light $ 675.00 $ 675.00 1.2 $ 80.00Piping $ 3.00 $ 150.00 50 N/AElectricity $ 0.07 $ 25.55 N/A N/A* 1 year is a pack (12) 5 micrion filters and (4) 3 micron filters Figure 6. Sample Results for Low-Consumption Household 37
  42. 42. Economic Analysis The accuracy of the economic analysis relies on the quality of the input data. For thepurposes of this study, the inputs have been fixed based on information obtained throughresearch and through communication with specific project representatives. However, theinherent value of the fiscal summation is in its flexibility to refine inputs based on clearercurrent research and on a greater contemporary conception of projects’ needs and of theirplanned 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 includingirrigation (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 alsobe analyzed for users with low, medium and high water demand and will be compared tothe cost savings from a reduced water utility bill. Outdoor Indoor/Outdoor Low Consumption $ 7,044 $ 7,936 Medium Consumption $ 7,528 $ 8,419 High Consumption $ 8,580 $ 9,471 Figure 7. Implementation Costs There is a model in Appendix K that calculates the monthly water bill for a Radiancecustomer based on the current rate structure. The cost of single rainwater collectionsystems is shown in Figure 7. Costs from this table represent the fixed, up-front cost of purchasing and of installinga rainwater collection system. They include the tank itself, the filter assembly, the filters,the UV lighting, the pumps, the roof washers and the piping. A tank size differs based on 38
  43. 43. the consumption rates. A 6,000-gallon tank was deemed appropriate for the low-consumption users, an 8,000 gallon for medium-consumption users and an 11,000 one forhigh-consumption users. These costs do not reflect the long-term maintenance costs suchas the replacing of filters and of pumps and the cost of electricity. These expenditureswill be included later in this report. The price of the outdoor systems does not includefiltration 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 andtransportation. This percentage is a variable and can be modified in the model for acustomer who wants to self-perform any or all of this work. Fiberglass has been selectedas the optimal tank material due to its long-term durability, its thermal properties and itsreasonable price, but alternatives do exist (Appendix J). A summary of all the expensesprovided 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 thesavings accrued on the water bill and on associated well water from using the Radianceservices. It should be duly noted that this expenditure differential would only be realizedif a very limited number of households implement a rainwater collection system becausethe 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 supportthe Radiance Water Supply Corporation) the corporation will be forced to raise rates onthe existing water usage to pay for its own fixed costs. This increase will theoreticallynullify any savings from a rainwater collection system on a community-wide application.The community-wide application is discussed in a supplementary scenario. 39
  44. 44. Cost Analysis: Medium Consumption, Indoor & Outdoor $35,000.00 $30,000.00 Costs $25,000.00 Savings Cumulative Cost ($) $20,000.00 $15,000.00 $10,000.00 $5,000.00 $- 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 Time (Yrs.) Figure 8. Cost Anaylsis Long-term expenses such as replacement costs and as electricity play a major role inthe economic feasibility of a rainwater collection system. A 2% (two) inflation factorwas 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 themonetary outflow outweighs the savings over a fifty-year lifecycle of the system. Thetwo lines actually diverge, demonstrating that the recurring maintenance costs are higherthan the continued payment to the Radiance water supply corporation. In total, nine figures were evaluated, varying the consumption from low, frommedium, 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 roofcatchment surface. These nine figures can be found in the Appendix I. In only onescenario did the savings from the rainwater collection system outweigh the expense of thesystem: 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 savingsreaped in approximately the thirty-sixth year of operation, largely because the large roofarea provides sufficient catchment area for the low-consumption user to sustain averagewater demands without supplement from the Radiance water supply corporation. This 40
  45. 45. independence will allow the user to forego the $22 monthly water service fee as well asthe municipal water fees. Cost Analysis: Low Consumption, Indoor & Outdoor, Large Roof $35,000.00 $30,000.00 Costs $25,000.00 Savings Cumulative Cost ($) $20,000.00 $15,000.00 $10,000.00 $5,000.00 $- 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 Tim e (Yrs.) Figure 9. Cost AnalysisImplementation of Community-Wide Rainwater Harvesting System Like most well water users, the Radiance community is faced with the imminentnecessity for a new well, as the existing loses its ability for adequate production tosupport community. The cost of drilling a new well is loosely comparable to that ofinstalling rainwater collection systems in the Radiance community, an effort that willlessen the strain on the existing well. However, the authors of this paper cannot forecastprecisely 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 forall of the households, respectively, in the Radiance community, and the correspondinggallons of rainwater used. The cost of implementing rainwater collection systems over half of the homes inRadiance slightly exceeds $136,000. This number assumes a 10% (ten) discount frombulk purchasing savings, and from delivery and from installation savings. Theimplementation expense of rainwater collection systems in all of the radiance homes is 41
  46. 46. roughly $258,000, which includes a discount factor of 15% (fifteen). All figures wereextrapolated from the average cost of a medium-consumption household for indoor andoutdoor use. Cost of Systems Rainwater Used per Year (gal) Half of Radiance $ 136,392 389,232 All of Radiance $ 257,630 778,464 Figure 10. Implementation Costs A potential economic benefit of implementing rainwater collection systems over alarge portion of the community is the savings from not replacing the current well as thestrain on existing well is drastically diminished. The depth of drilling [to reach a watersource] will determine the expense of drilling a new well, but the likely sum centersaround $40,000. It appears that the amount of money required in attaining this $40,000savings is much larger than the actual savings itself, deigning this scenario unfeasiblefrom an economic standpoint. As previously mentioned, the amount of water savings tomake the existing well sustainable is not known. Additional analysis should beperformed to further understand this issue. The table above estimates gallons ofrainwater used based on the medium consumption household for indoor and outdoor useso 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, thecost of implementing rainwater collection systems to the Radiance community should becompared to the foregone cost of other water sources. 42
  47. 47. RecommendationsManagement Recommendations To assist the homeowners, we recommend that the Radiance Water SupplyCorporation contact a rainwater system installer to consult. This consultant wouldprovide general design, management, routine maintenance guidelines and assistance forall homes and would be on call if issues subsequently should arise. As each rainwatersystem will be run independently, each individual homeowner will manage their owncollection system, and should monitor tank levels, maintain unobstructed gutters andfirst-flush devices, change out filters regularly, maintain disinfection equipment and testnot only the water quality and but also the system functions regularly.Monitoring Recommendations The Texas Manual for Rainwater Harvesting recommends that both county healthdepartment and city building code staff be consulted concerning the construction of therainwater collection system and the subsequent safe, sanitary operations. It is assumedthat the rainwater system installer will contact the necessary parties. Because the watercollected here will be potable, in accordance with the recommendations from the TexasManual for Rainwater Harvesting, we recommend that the harvested rainwater be testedquarterly for fecal coliforms, pathogens, and pesticides by a commercial analyticallaboratory [Texas Manual for Rainwater Harvesting 2002]. Additionally, althoughneither federal nor state guidelines exist for harvested water quality, one should check theEnvironmental Protection Agency’s website [www.epa.gov/safewater/mcl.html] for a listof the latest drinking water requirements before ordering specific tests. Mostcommercial laboratories [consult your local Yellow Pages: Laboratories—Analytical andTesting for a list of local testing laboratories] will test for pathogens, metals andpesticides and the Texas Department of State Health Services[www.dshs.state.tx.us/lab/default.shtm] will test for fecal coliforms. 43
  48. 48. Appendix A: Safety CodesExcerpt 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 andcontrol of public drinking water systems in the state. The statute requires that thecommission ensure that public water systems: supply safe drinking water in adequatequantities, are financially stable and technically sound, promote use of regional and area-wide drinking water systems, and review completed plans and specifications and businessplans 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 compliancehistory in approving new or modified public water systems.(b) Reason for this subchapter and minimum criteria. This subchapter has been adopted toensure regionalization and area-wide options are fully considered, the inclusion of alldata essential for comprehensive consideration of the contemplated project, orimprovements, additions, alterations, or changes thereto and to establish minimumstandardized public health design criteria in compliance with existing state statutes and inaccordance with good public health engineering practices. In addition, minimumacceptable financial, managerial, technical, and operating practices must be specified toensure 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 beginconstruction of a public drinking water supply system unless the executive directordetermines the following requirements have been satisfied and approves construction ofthe proposed system. (1) A person proposing to install a public drinking water system within theextraterritorial jurisdiction of a municipality; or within 1/2-mile of the corporateboundaries of a district, or other political subdivision providing the same service; orwithin 1/2-mile of a certificated service area boundary of any other water serviceprovider 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 thepayment 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 requestmust be accompanied by evidence documenting the financial hardship. (3) A person who is not required to complete the steps in paragraph (1) of thissubsection, or who completes the steps in paragraph (1) of this subsection and is deniedservice or determines that the existing providers cost estimate is not feasible for thedevelopment 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
  49. 49. (d) Submission of plans. (1) Plans, specifications, and related documents will not be considered unless they havebeen prepared under the direction of a licensed professional engineer. All engineeringdocuments must have engineering seals, signatures, and dates affixed in accordance withthe rules of the Texas Board of Professional Engineers. (2) Detailed plans must be submitted for examination at least 30 days prior to the timethat approval, comments or recommendations are desired. From this, it is not to beinferred that final action will be forthcoming within the time mentioned. (3) The limits of approval are as follows. (A) The commissions public drinking water program furnishes consultation services asa reviewing body only, and its licensed professional engineers may neither act as designengineers nor furnish detailed estimates. (B) The commissions public drinking water program does not examine plans andspecifications in regard to the structural features of design, such as strength of concrete oradequacy of reinforcing. Only the features covered by this subchapter will be reviewed. (C) The consulting engineer and/or owner must provide surveillance adequate to assurethat facilities will be constructed according to approved plans and must notify theexecutive director in writing upon completion of all work. Planning materials shall besubmitted 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 shallconform to the following requirements. (1) Engineering reports are required for new water systems and all surface watertreatment plants. Engineering reports are also required when design or capacitydeficiencies are identified in an existing system. The engineering report shall include, atleast, 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 ofsystem operation under normal and emergency conditions; and (H) the adequacy of the facilities with regard to delivery capacity and pressurethroughout the system. (2) All plans and drawings submitted may be printed on any of the various papers whichgive 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 shallbe shown. (B) The location of all abandoned or inactive wells within 1/4-mile of a proposed wellsite shall be shown or reported. (C) If staged construction is anticipated, the overall plan shall be presented, eventhough a portion of the construction may be deferred. (D) A general map or plan of the municipality, water district, or area to be served shallaccompany each proposal for a new water supply system. 45
  50. 50. (3) Specifications for construction of facilities shall accompany all plans. If a process orequipment which may be subject to probationary acceptance because of limitedapplication 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 manufacturercovering acceptable performance. The specifications shall include a statement that such abonded guarantee will be provided to the owner and shall also specify those conditionsunder which the bond will be forfeited. Such a bond will be transferrable. The bond shallbe retained by the owner and transferred when a change in ownership occurs. (4) A copy of each fully executed sanitary control easement and any otherdocumentation demonstrating compliance with §290.41(c)(1)(F) of this title (relating toWater Sources) shall be provided to the executive director prior to placing the well intoservice. Each original easement document, if obtained, must be recorded in the deedrecords 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 majorimprovements to existing water systems must be in conformity with applicablecommission rules.(f) Submission of business plans. The prospective owner of the system or the personresponsible for managing and operating the system must submit a business plan to theexecutive director that demonstrates that the owner or operator of the system hasavailable the financial, managerial, and technical capability to ensure future operation ofthe system in accordance with applicable laws and rules. The executive director mayorder the prospective owner or operator to demonstrate financial assurance to operate thesystem in accordance with applicable laws and rules as specified in Chapter 37,Subchapter O of this title (relating to Financial Assurance for Public Drinking WaterSystems and Utilities), or as specified by commission rule, unless the executive directorfinds that the business plan demonstrates adequate financial capability. A business planshall include the information and be presented in a format prescribed by the executivedirector. 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 theproposed system, copies of written requests seeking to obtain service from each of thosedrinking 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 watersystem and any identifiable future owners of the drinking water system; (7) identification of any other businesses and public drinking water system(s) owned oroperated by the applicant, owner(s), parent organization, and affiliated organization(s); (8) an operations and maintenance plan which includes sufficient detail to support thebudget estimate for operation and maintenance of the facilities; (9) assurances that the commitments and resources needed for proper operation andmaintenance of the system are, and will continue to be, available, including the 46
  51. 51. qualifications of the organization and each individual associated with the proposedsystem; (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 offeredto capital providers; (12) a notarized statement signed by the owner or responsible person that the businessplan has been prepared under his direction and that he is responsible for the accuracy ofthe information; and (13) other information required by the executive director to determine the adequacy ofthe business plan or financial assurance.(g) Business plans not required. A person is not required to file a business plan if theperson: (1) is a county; (2) is a retail public utility as defined by TWC, §13.002, unless that person is a utility asdefined by that section; (3) has executed an agreement with a political subdivision to transfer the ownership andoperation of the water supply system to the political subdivision; or (4) is a noncommunity nontransient water system and the person has demonstratedfinancial 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 receivingwritten approval of plans and specifications and, if required, approval of a business planfrom the executive director. No person may begin construction of modifications to apublic water system without providing notification to the executive director andsubmitting and receiving approval of plans and specifications if requested in accordancewith subsection (j) of this section. (2) The executive director shall be notified in writing by the design engineer or theowner before construction is started. (3) Upon completion of the water works project, the engineer or owner shall notify theexecutive director in writing as to its completion and attest to the fact that the completedwork is substantially in accordance with the plans and change orders on file with thecommission.(i) Changes in plans and specifications. Any addenda or change orders which mayinvolve a health hazard or relocation of facilities, such as wells, treatment units, andstorage tanks, shall be submitted to the executive director for review and approval.(j) Changes in existing systems or supplies. Public water systems shall notify theexecutive director prior to making any significant change or addition to the systemsproduction, treatment, storage, pressure maintenance, or distribution facilities. Publicwater systems shall submit plans and specifications for the proposed changes uponrequest. Changes to an existing disinfection process at a treatment plant that treats surfacewater or groundwater that is under the direct influence of surface water shall not beinstituted without the prior approval of the executive director. (1) The following changes are considered to be significant: 47
  52. 52. (a) proposed changes to existing systems which result in an increase or decrease in production, treatment, storage, or pressure maintenance capacity;(B) proposed changes to the disinfection process used at plants that treat surface water orgroundwater that is under the direct influence of surface water including changesinvolving the disinfectants used, the disinfectant application points, or the disinfectantmonitoring points; (C) proposed changes to the type of disinfectant used to maintain a disinfectantresidual in the distribution system; (D) proposed changes in existing distribution systems when the change is greater than10% of the existing distribution capacity or 250 connections, whichever is smaller, orresults in the water systems inability to comply with any of the applicable capacityrequirements of §290.45 of this title (relating to Minimum Water System CapacityRequirements); and (E) any other material changes specified by the executive director. (2) The executive director shall determine whether engineering plans and specificationswill be required after reviewing the initial notification regarding the nature and extent ofthe modifications. (A) Upon request of the executive director, the water system shall submit plans andspecifications 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 toWater Districts), the executive director will not require another state agency or a politicalsubdivision to submit planning material on distribution line improvements if the entityhas 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 thatare employed by the political subdivision and must be separate from, and not subject tothe review or supervision of, the engineering staff or firm charged with the design of thedistribution extension under review; (ii) a licensed professional engineer on the internal review staff determines andcertifies in writing that the proposed distribution system changes comply with therequirements of §290.44 of this title (relating to Water Distribution) and will not result ina violation of any provision of §290.45 of this title; (iii) the state agency or political subdivision includes a copy of the writtencertification described in this subparagraph with the initial notice that is submitted to theexecutive director. (C) Unless plans and specifications are required by Chapter 293 of this title, theexecutive director will not require planning material on distribution line improvementsfrom any public water system that is required to submit planning material to another stateagency 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 astate statute or local ordinance requires the planning materials to be submitted to the otherstate agency or political subdivision and a copy of the written certification that is requiredin 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 existingsystem which does not meet the requirements of all sections of this subchapter will not be 48

×