GEORGETOWN, TEXAS IRRIGATION SYSTEM MASTER PLAN AND RECLAIMED WATER PROGRAM

Transcription

1 GEORGETOWN, TEXAS IRRIGATION SYSTEM MASTER PLAN AND RECLAIMED WATER PROGRAM ABSTRACT Patrice A. Melançon,* Roger E. Schenk, Jr.;** Michael R. Stasny** *Camp Dresser & McKee Inc. (CDM) A Riata Trace Parkway, Suite 210 Austin, Texas **CDM - Austin, City of Georgetown, Texas The City of Georgetown, Texas is a rapidly growing community located about 30 miles north of Austin in central Texas. Georgetown is situated on the recharge zone of the Edwards Aquifer, a major groundwater resource in central Texas. The City relies on groundwater resources for about half of its drinking water supply. The other half of its drinking water supply is provided by Lake Georgetown, located about 5 miles west of downtown. Historically, the City of Georgetown began its current reclaimed water program in 1979 when it started providing recycled water from its San Gabriel Wastewater Treatment Plant (WWTP) to nearby Southwestern University for golf course irrigation. This project represents the first known application of reclaimed water over the Edwards Aquifer Recharge Zone. Recent upgrades at the San Gabriel WWTP now provide tertiary effluent treatment to meet Type I reclaimed water standards. This has allowed Southwestern University to serve many other athletic fields in addition to the golf course minimizing their potable water demands that formerly served as the irrigation source. The Southwestern University reuse system has operated for over 25 years. In September 1998, the City applied to the Texas Commission on Environmental Quality (TCEQ) for a Citywide 30 TAC water reuse authorization to begin the development of a comprehensive reclaimed water program to supplement their non-potable irrigation needs. This reuse system was intended to augment a previously established groundwater irrigation system to help provide non-potable water for large-scale irrigation demands. On September 1, 1999, the City of Georgetown was issued one of the State s first reuse authorizations. The City has aggressively developed portions of the approved citywide reuse plan to provide irrigation water for San Gabriel Park, Berry Creek Country Club, and Georgetown Country Club among others. In September 2004, the City began the development of its first Irrigation Water System Master Plan and the related distribution system model. The Irrigation Water Master Plan system model evaluates all known and planned irrigation demands, supply source waters, storage tanks, pump stations, and transmission pipelines. Irrigation flows within the system are modeled for existing conditions, 2015 conditions, and 2025 conditions. The system s ability to meet expected water demands for these three planning horizons was also evaluated. This Irrigation Water System Master Plan will guide the City of Georgetown as it prioritizes future Capital Improvement Program projects that will sustain its water supplies with the beneficial reuse of reclaimed water. 6219

2 KEYWORDS Reclaimed Water Irrigation, Irrigation System Master Plan, Water Reuse, Recycled Water INTRODUCTION The City of Georgetown, Texas is a rapidly growing community of about 30,000 residents and is located about 30 miles north of Austin in central Texas. Georgetown is situated on the recharge zone of the Edwards Aquifer, a major groundwater resource in Texas. The City relies on groundwater resources for about half of its drinking water supply. The other half of its drinking water supply is provided by Lake Georgetown, located 5 miles west of downtown. Historically, the City of Georgetown has utilized ground water resources to meet most of its irrigation customer s demands by providing untreated ground water. In other instances it has provided treated water (of potable water quality). The City began its first irrigation system that utilized reclaimed water (highly treated wastewater effluent) in This initial water reuse system provided reclaimed water to the Kurth-Landrum Golf Course located on the eastern portion of the Southwestern University campus. The source of the irrigation water for Southwestern University golf course was the San Gabriel Wastewater Treatment Plant (WWTP) that is located north of the college campus. This reuse project represents the first known application of reclaimed water over the sensitive Edwards Aquifer recharge zone. Recent upgrades to the San Gabriel WWTP now provide tertiary filter treatment and produces Type I reclaimed water (for unrestricted use) to be used for athletic field irrigation in addition to the golf course irrigation. This application has minimized the potable water demand that was formerly used to irrigate those areas. The Southwestern University reuse system has now been in operation for more than 25 years. On September 1, 1999, the City of Georgetown was issued one of the first reuse authorizations approved by the Texas Commission on Environmental Quality (TCEQ) under 30 TAC to begin the development of a comprehensive reclaimed water program to supplement their nonpotable irrigation needs. This reuse system was intended to augment the previously established ground water irrigation system for Sun City Golf Course to help provide non-potable water for large-scale irrigation demands. The City has aggressively developed portions of the approved citywide reuse plan to provide irrigation water for San Gabriel Park and the Georgetown Country Club among others. The City is now in the process of planning and constructing a reclaimed water system infrastructure that will also include its Pecan Branch and Dove Springs WWTP facilities. With this planning effort, the City is establishing one of the larger water reuse systems among the midsize cities of Texas. In order to most cost-effectively proceed with these ambitions, the City commissioned the preparation of its initial Irrigation Master Plan study to provide a distribution system model of ground water and reclaimed water resources that may be used to meet future irrigation demands and to evaluate the implementation of system capital improvements to accommodate these future demands. 6220

3 IRRIGATION SYSTEM MASTER PLAN The City of Georgetown retained CDM to develop an Irrigation System Master Plan. The City currently uses some reclaimed water from the San Gabriel Wastewater Treatment Plant (WWTP), along with untreated ground water from Wells #7 and #8. The City desires to eventually incorporate reclaimed water from the Pecan Branch and Dove Springs WWTPs and reduce, or potentially eliminate, the need for ground water irrigation usage. In addition, the City would like to convert the source of water to reclaimed water for some of the existing irrigation customers who currently use potable water. Data Collection The City of Georgetown supplied data on the existing irrigation system, existing and future parks, existing and future irrigation sites, and billing data for customers. Other data sources included interviews with current large scale irrigation users including Southwestern University personnel, area golf course managers, and the contractor planning toll plaza areas associated with the construction of State Highway 130 that would require irrigation. IRRIGATION DISTRIBUTION SYSTEM City Staff provided GIS data showing existing and planned distribution mains. This data was verified and updated using available as-built and/or record drawings. Figure 1 shows the distribution system. Irrigation Water Sources The current sources for the irrigation distribution system are Ground water Wells #7 and #8 near the airport and treated effluent from the San Gabriel Wastewater Treatment Plant (WWTP). Ground water Well # 8 can produce up to 1300 gallons per minute (gpm), (1.9 million gallons per day (MGD)). Ground water Well #7 can produce up to 750 gpm (1.1 MGD). The San Gabriel WWTP currently produces, on average, 1050 gpm (1.5 MGD). Other sources that could be added to the system include treated effluent from the Dove Springs WWTP average flow of 700 gpm (1 MGD) and from the Pecan Branch WWTP average flow of 350 gpm (0.5 MGD) with anticipated expansion to 700 gpm (1 MGD). Irrigation Water Storage Facilities The three main storage facilities associated with the irrigation distribution system are the Sun City Golf Course Ponds, the Airport Ground Storage Tank, and the Park Ground Storage Tank. The Sun City Golf Course ponds consist of two ponds, one of the White Wing courses and one on the Legacy Hills providing approximately 10.5 MG of storage at White Wing and 3.5 MG of storage at Legacy Hills. These ponds are filled from the Airport Ground Storage Tank Pump Station by gpm pumps (1,300 gpm total capacity). 6221

4 The Airport Ground Storage Tank has a capacity of 1.5 MG and is currently filled by the two ground water wells described in Section 2.2. In the future, this tank will also be filled from the Pecan Branch WWTP (PBWWTP), rated at 1.5 MGD treatment capacity. MELANCONPA AUSSVR1\GIS\City_Georgetown\IrrigSysMP\Report Figures\Figure2-1.mxd 4/20/2005 KJ White Wing Pond FM 2338 JIM HOGG PASS S LAKEWOOD DR RED POPPY TRL LEGEND FM 2243 FOX HOME LN CAMP DR SEDRO TRL PENNY LN WOODLAKE DR CROSBY ST CEDAR BREAKS RD TEXAS DR STATE HIGHWAY 195 KJ Legacy Hills Pond WILDWOOD DR WESTBURY LN D B WOOD RD W STATE HIGHWAY 29 WILLIAMS DR BOOTY'S CROSSING RD OAK RIDGE RD TEN OAKS DR LEANDER RD PRIVATE RD OAK BRANCH DR STETSON TRL BLACKSMITHS DR VERDE VISTA MIRAMAR DR CASSIDY DR "J WWTP Location UT Storage Tanks/Clearwell KJ Pond Wells "M Well 7 "M Well 8 Irrigation Lines Existing Future Streets LONE STAR DR OAK CREST LN RIVER CHASE BLVD WOLF RD SHELL RD SEVILLA DR RIVER RD SPRING VALLEY RD LOVIE LN MESA DR CR 265 BONNET LN SERENADA DR WAGON WHEEL TRL PARKER DR LAKEWAY DR SUSANA DR DAWN DR S INTERSTATE 35 C R 147 SHELL STONE TRL LOGAN RANCH RD RANCH RD RIDGE OAK DR. TAMARA DR E SEQUOIA TRL OAK LN CHAMPIONS DR CAVU RD BRANGUS RD "M C R 234 Airport Tank UT "M NORTHWEST BLVD PARK LN W UNIVERSITY AVE LUTHER DR RIVERY BLVD RIVER HILLS DR LAS COLINAS DR RAILROAD AVE S INTERSTATE 35 1 inch equals 6,000 feet WEST ST C R 116 DEER TRL SIERRA DR TOLEDO TRL WILLIAMS DR FOREST ST LEANDER ST UT Park Tank SNEAD DR S AUSTIN AVE BERRY CREEK DR E 2ND ST S CHURCH ST E 21ST ST ASH ST Berry "J Creek GANN ST N HOLLY ST E 19TH ST S PINE ST Well 8 N AUSTIN AVE E 7TH ST VALLEY DR FM 1460 INNER LOOP SE C R 143 Well 7 MAPLE ST C R 166 P R 914 CHI CHI DR AIRPORT RD VINE ST TOWER DR E MORROW ST C R 151 MEDA ST N INTERSTATE 35 MARKET ST C R 196 NE INNER LOOP FM 971 SanGabe Cl Contact Basins UT "J San Gabriel Tank SMITH CREEK RD VINE ST HUTTO RD N INTERSTATE 35 STEPHEN LN JAN LN N INTERSTATE 35 CLARIS LN N INTERSTATE 35 LAZY RD SUNNYVALE E UNIVERSITY AVE C R 110 P R 916 BELMONT DR CARLSON CV C R 110 C R 111 C R 142 MEADOW CREST DR BERRY LN C R 144 GREEN ACRES GROVE LN FM 972 C R 141 C R 150 C R 152 C R 140 Pecan Branch Clearwell UT "J EASTVIEW DR INDIAN CREEK DR CHURCHILL FARMS DR C R 103 C R 104 Dove Springs Clearwell UT "J C R 102 RUSK LN E STATE HIGHWAY 29 ALYSON DR C R 105 C R 162 C R 149 C R 194 RICHARD RD C R 105 CITY OF GEORGETOWN, TEXAS IRRIGATION DISTRIBUTION SYSTEM COMPONENTS FIGURE

5 The Park Ground Storage Tank has a capacity of 1.0 MG and has gpm and 1 30 gpm pumps to supply water to the Georgetown Country Club Golf Course. This tank is filled from the San Gabriel WWTP by gpm, gpm, and 1 75 gpm pumps (2,175 gpm total pumping capacity). The PBWWTP currently does not have pumping available to provide water to the irrigation distribution system. Its current storage capacity is limited to 1 18,500 gallon clearwell. The Dove Springs WWTP (DSWWTP) currently does not have pumping available to provide water to the irrigation distribution system. Its current storage capacity is limited to 1 45,000 gallon converted chlorine contact basin. IRRIGATION WATER CUSTOMERS Existing Customers Billing records from City Staff provided monthly usage of irrigation water for years 2002, 2003, and These records were evaluated to determine the demand that would be placed on the hydraulic model to evaluate adequacy of the existing system. For a worst case scenario, the maximum monthly demand was used. Table 1 outlines existing customers and demand. Table 1 - Existing Irrigation Water Customers and Demands Account Customer Max Month (kgal/mo) Max Day (gpm) Southwestern Univ Non-Potable Irrigation 8, Sun City TX (Golf Course) 50,890 5, Georgetown Country Club 3, Georgetown Football Field Baseball Fields & Park Irrigation Non-Potable Irrigation / Park Baseball Fields Maximum monthly demands were converted to daily amounts based on an assumption that irrigation occurs on 20 out of 30 days a month. Daily demands were converted to a gallons per minute application rate by assuming that irrigation occurs for 8 hours in the evening. These two assumptions are generally consistent with information provided by golf course managers that were contacted. The maximum daily application rates are also shown in Table 1. The conversions are shown in the equation below: kgal mo 1000gal kgal mo 20days day 8hrs hr 60 min = gpm While there are billing records available for Southwestern University and the Georgetown Country Club Golf Course, both of these customers have a contract with the City of Georgetown 6223

6 outlining a maximum daily allowable delivery of irrigation water. Southwestern University is limited to 1 MGD (2,083 gpm under current irrigation application assumptions). The Georgetown Country Club is limited to 400,000 gpd (833 gpm under current irrigation application assumptions). For a worst case evaluation, it was assumed that these customers are using their entire contract amount. POTENTIAL FUTURE CUSTOMERS Billing records from City Staff also provided monthly usage of potable water for years 2002, 2003, and There are a number of current potable water customers using potable water for irrigation. Approximately 250 of them have a separate meter to track irrigation use. These records were examined to evaluate the economics and feasibility of converting this irrigation demand to the irrigation distribution system. Currently, potable water use is charged at conservation rates, which includes an increasing block rate pricing structure. Table 2 outlines potable water rates currently in effect. Table 2 - Current Georgetown Potable Water Billing Rates Gallons Used Cost/kGal 0-19,000 $ ,000-29,000 $ ,000-39,000 $ ,000+ $6.00 The cost for irrigation water is currently $0.85/kGal regardless of amount used. All service addresses were geo-located and best professional judgment used to eliminate those customers that were likely too far away from the distribution system. Billing records from those remaining were processed to determine the average annual use and identify those customers whose average annual use exceeds 0.5 MG. These customers with higher irrigation use have a greater potential for savings. To evaluate potential customer savings, it was necessary to be able to calculate the annual cost of irrigation demands met using potable water versus irrigation water. Given the tiered potable rate structure and seasonal variations in water use, calculations for each month are necessary to determine annual costs for potable water. A number of representative data sets were evaluated to determine the actual calculated cost per month and per year. From those representative data sets, it was determined that the cost of potable irrigation water for the maximum monthly usage is about 20% of the total annual cost for any given customer under conservation rates. For the subset of potable customers being evaluated, a maximum monthly demand from billing records was used to calculate cost under conservation rates. This cost was scaled up to an annual costs based on the assumption that the cost for the maximum month makes up 20% of the total annual cost. Then, based on annual demand for the corresponding year, an irrigation water cost 6224

7 was calculated at current irrigation rates. The difference between these two amounts represents potential customer savings. Most customers would require some length of distribution line to connect to the irrigation distribution system. A cost to connect was estimated based on the distance from the geolocated customer to the system and an assumption that an 8-inch line, at a cost of $50/linear foot (LF), would be needed. Note that this planning study did not evaluate whether or not connecting to the system would require tunneling under a riverbed or an interstate. This factor should be evaluated as part of the preliminary engineering design for potential customer conversions. This cost to connect was compared to the potential customer savings. The ratio of capital investment required to connect to the system to the potential customer savings represents the payback period for a particular customer. In addition, parks and open spaces were considered for connection to the irrigation distribution system and include Rivery Park and Trail, VFW Park, Pecan Branch Park, and the Toll Plaza at the intersection of Hwy 29 and future SH 130. The current irrigation distribution system runs through Rivery Park and Trail, so there will be minimal cost to connect. Pecan Branch Park is adjacent to the Pecan Branch WWTP, again with minimal cost to connect. The other two sites are within a half-mile of the existing distribution system. For these potential customers with no billing history, irrigation demand was estimated using an irrigation planning demand factor of 2 in/week during the heat of summer. The same assumptions of irrigation occurring 20 out of 30 days a month for 8 hours in the evening were used in calculating an application rate. This irrigation planning demand factor was chosen based on information from a Travis County Cooperation Extension Agent; Williamson County Cooperative Extension Agent; and Guidelines for Water Reuse developed for USEPA by CDM in 1992 and most recently in The above irrigation assumptions were used to determine a maximum monthly demand. That demand, along with an annual cost scaling factor of 5 (determined above from potable billing records) and the current conservation rates for potable water, was used to determine an approximate annual cost for satisfying demand with potable water. Determination of an annual cost for using irrigation water to meet the irrigation demand required a ratio of maximum monthly demand to average monthly demand. This ratio was determined by evaluation of billing records for other park customers and was found to be approximately 3:1. Maximum monthly demands were divided by 3 to establish an average monthly demand. That average was multiplied by the current rate for irrigation water ($0.85/kGal) and then multiplied by 12 months to get an annual cost for meeting irrigation demand using irrigation water. Table 3 shows the economic analysis for these four potential customers. 6225

8 Table 3 - Annual Economic Analysis for Potential Future Irrigation System Customers Site Acres to Irrigate Cost for Potable Water Cost for Irrigation Water Potential Annual Savings Distance to Pipe (ft) Cost to Connect 1 Pecan Branch Park 20 $136,248 $15,509 $120,739 0 $ VFW 10 $67,824 $7,755 $60, $42, Payback Period (Yrs) Rivery Park & Trail 30 $204,672 $23,264 $181,408 0 $ Large Toll Interchange 20 $136,248 $15,509 $120, $90, Note: Based on $50/LF cost The two sites that would have a significant cost to connect have a payback period of less than one year. DISTRIBUTION SYSTEM OPERATION Existing System Operation In order to evaluate whether the existing system can meet the irrigation demands at the times they are needed, it is necessary to understand what the maximum monthly demands are and what infrastructure provides water to meet those demands. Table 4 outlines current customers, their maximum monthly demands, and what portion of the system supplies reclaimed water to those customers. Table 4 - Existing System Design Irrigation Demands Irrigation Demand Address Design Demand (gpm) Served by Georgetown Country Club Country Club Rd 833 Park Tank Southwestern Univ Non-Potable Irrigation N College St 2,083 Georgetown Football Field 107 Stadium Dr 76 Baseball Fields & Park Irrigation 435 E Morrow St 25 Non-Potable Irrigation / Park 443 E Morrow St 19 Baseball Fields 521 E Morrow St 10 San Gabriel WWTP Clearwell San Gabriel WWTP Clearwell San Gabriel WWTP Clearwell San Gabriel WWTP Clearwell San Gabriel WWTP Clearwell Sun City TX Comm Assoc Sun City Golf Course Ponds 5,301 Airport Tank Note: Demand is based on maximum amount allowed to be taken under current contract with City of Georgetown. 6226

9 A spreadsheet model was used to evaluate flows into and out of the system water supply and storage facilities to determine if irrigation water demands can be met with existing supplies and refill existing storage facilities. The Park Tank (1.0 MG GST) currently only serves the Georgetown Country Club. Meeting the irrigation demand in the evening irrigation hours requires that the tank be filled at a rate of 420 gpm during non-irrigation hours. It also requires maximum storage of 0.43 MG. Both of these requirements can currently be met. The tank can be filled by the 420 gpm pump at the SGWWTP. There are gpm and 1 30 gpm pumps at the Park Tank to provide water to the Georgetown Country Club Golf Course during evening irrigation hours. It should be noted there is enough total capacity available (1,230 gpm), but not enough firm capacity (630 gpm). There are number of customers that are served directly off of the San Gabriel WWTP (SGWWTP) Clearwell (350,000 gal GST) as they are upstream of the Park Tank and cannot be served by that facility under the current system configuration. The SGWWTP must be able to provide and store irrigation water to fill the Park Tank during the day and meet irrigation demands totaling 2,213 gpm in the evening irrigation hours. The SGWWTP currently produces an average of 1,050 gpm (1.5 MG). Because this flow is not constant, but based on a diurnal pattern, and the irrigation demands occur only at night, the evaluation had to take into account that variation in flow. A diurnal curve, based on current average Georgetown plant flows, was applied to the average flow. Under current conditions, the SGWWTP is able to provide enough flow to fill the Park Tank and meet current irrigation demands. However, this would require 0.75 MG of storage. Currently, there is only 0.35 MG of storage available. In addition, there is not enough pumping capacity to meet the 2,213 gpm demand during the evening irrigation period. There is currently 2,175 gpm total pumping capacity and 1,335 gpm firm pumping capacity at the Plant. Note that under demands reflecting current billing records (as opposed to maximum allowed under contract), Southwestern is only taking a maximum of 889 gpm, for a total demand of 1,019 gpm. There is enough firm pumping capacity and storage available to meet these current demands. The Airport Tank currently only serves to fill the Sun City Golf Course Ponds. These ponds have a combined irrigation demand of 5,301 gpm in the evening hours. Meeting this demand and maintaining storage levels requires 1,750 gpm be supplied on a constant basis over the entire day. Currently, the Airport Tank Pump Station only has a total capacity of 1,300 gpm. Because there is so much storage at the Golf Course ponds, an alternative evaluation was carried out to determine if this pumping capacity could provide service if it was assumed that irrigation occurred 2 out of every 3 evenings. This would be consistent with our assumption that irrigation occurs 20 days out of every 30 a month. Under this scenario, the 1,300 gpm available will be sufficient. However, it should be noted that the 1,300 gpm available is the total pumping capacity available, not the firm capacity. Because the Airport Tank is merely serving to pass flow through (what goes in, also goes out), the available storage capacity is being under-utilized. The current ground water well capacity is sufficient to meet the demand. A WaterCAD model was developed to look at other factors, such as pipe velocity and headloss in the system. The WaterCAD model indicated high headloss and velocities in the 8-in pipe that 6227

10 supplies the Legacy Hill Golf Course pond, indicating that this pipe is likely undersized. While this section of the system does not belong to the City, it might be worthwhile to discuss this potential bottleneck with the appropriate personnel at Sun City. Additionally, the 6- and 8-inch lines that serve irrigation water from the SGWWTP to Southwestern University show very high headloss and velocities, indicating those lines are likely undersized to provide the contracted amount of water. Even under demand conditions reflecting current billing records, the 6 line has a velocity in excess of 10 fps. This section of the system belongs to Southwestern, but it might be worthwhile to discuss this potential bottleneck with them. Future Condition System Operation In the future, the City plans to connect the Pecan Branch and Dove Springs WWTPs to the irrigation distribution system. Pecan Branch WWTP will be connected to lessen the dependence on ground water to meet irrigation needs. Table 5 outlines irrigation demands for the future scenario. As described earlier, a spreadsheet model was used to evaluate flows into and out of the system water supply and storage facilities to determine if irrigation water demands can be met with future supplies and refill storage facilities. In the future, the Park Tank (1.0 MG GST) will serve the Georgetown Country Club as well as additional customers to the west of the tank and pump station. These additional demands bring the total demand from the Park Tank to 1,930 gpm. Two of the largest users would be Rivery Park/Trail (peak demand of 713 gpm) and VFW Park (peak demand of 238 gpm). Providing this amount in the evening irrigation hours requires that the tank be filled at a rate of 950 gpm during non-irrigation hours. It also requires maximum storage of MG. Both of these requirements currently can be met. However, there is not enough pumping capacity currently available to meet the irrigation demand in the evening. The Park Tank Pump Station has 1,230 gpm total capacity and only 630 gpm firm capacity and irrigation demands are 1,930 gpm over the 8-hour irrigation period. While there is enough water and pumping capacity available to fill the Park Tank so that there will be enough water to meet the total irrigation demand, there is not enough pumping capacity at the Park Tank to deliver the water at the necessary rate. Note that based on max day billing records, the Country Club Golf Course uses 388 gpm of irrigation water and 30 gpm of potable water for a total need of 418 gpm at the Country Club. This, along with the other future demands, comes to a total actual demand of 1,516 gpm. This is still more flow than is able to be pumped. Either the pump station will have to be upgraded, there will be a need to irrigate over a longer period of time at a lower rate, or some of these potential customers will not be able to be served. Velocities in the line from the Park Tank out to the Georgetown Country Club are projected to be as high as 7 fps. If and when a decision is made to add Rivery Park/Trail and VFW Park to the reclaimed system, consideration should be given to providing a parallel line. 6228

11 As in the existing condition, there are a number of customers that will be served directly off of the San Gabriel WWTP (SGWWTP) Clearwell (350,000 gal GST) as they are upstream of the Park Tank and cannot be served under the current system configuration. The SGWWTP must be able to provide and store irrigation water to fill the Park Tank during the day at a rate of 950 gpm and meet irrigation demands totaling 2,913 gpm in the evening irrigation hours. As in the existing condition, the plant provides irrigation water at a rate that varies based on the average diurnal curve. Under future conditions, the SGWWTP is not able to provide enough flow to fill the Park Tank and meet future irrigation demands. Under available flow rates, the plant is able to fill the Park Tank, but can only meet 1,263 gpm of the needed 2,913 gpm irrigation demand in the future. This is a short fall of 1,650 gpm of irrigation demand. However, the existing clearwell (0.35MG) provides adequate storage at this reduced irrigation demand. In order to meet the entire future irrigation demand, the plant would need to produce on average 1,600 gpm of irrigation water and would require 0.88MG of storage. There would also need to be increases to pumping capacity to be able to move water at the needed rate of 2,913 gpm. Some of the shortfall might be met from the Dove Springs WWTP. As outlined in Section 4.2.5, the DSWWTP could potentially meet another 1,499 gpm of demand in the evening irrigation hours. This would require additional storage at DSWWTP. In the future scenario, the Airport Tank will serve to fill the Sun City Ponds, as well as meeting irrigation demands for other customers downstream of the Airport Pump Station. This amounts to 1,267 gpm. An assumption was made that the Airport Tank would be able to serve the Pecan Branch Park irrigation needs as there should be enough difference in elevation head to allow for adequate pressure at the Park. 6229

12 Table 5 - Future Irrigation Demands Irrigation Demand Address Max Month Demand (gpm) Served by Sun City Tx Community Association Sun City Golf Course Ponds 5301 Airport Tank Sun City Tx Community Association 2 Texas Dr C 259 Airport Tank Sun City Tx Community Association 151 Dove Hollow Trail 111 Airport Tank Sun City Tx Community Association 1 Texas Drive 66 Airport Tank Sun City Tx Community Association 301 Del Webb Blvd 67 Airport Tank Sun City Tx Community Association 650 Sun City Blvd 41 Airport Tank The Worship Place 811 Sun City Blvd 70 Airport Tank Del Webb 204 Coyote Trail 38 Airport Tank Sun City Tx Community Association 200 Del Webb Blvd 37 Airport Tank Live Oak Development 400 Del Webb Blvd 26 Airport Tank Sun City Tx Community Association 131 Verbena Dr 25 Airport Tank Berry Creek Country Club 449 Champions Drive 52 Airport Tank Pecan Branch Park Near PBWWTP 475 Airport Tank Large Toll Interchange Intersection of SH 130 & SH Dove Springs WWTP Clearwell Summercrest HOA Inc 1207 Summercrest Blvd 73 Dove Springs WWTP Clearwell Berry Creek Partners 98 Stonehedge Blvd 81 Dove Springs WWTP Clearwell Sterling House 2600 E University 22 Dove Springs WWTP Clearwell Georgetown Country Club 1500 Country Club Rd 833 Park Tank Rivery Park Rivery Blvd. 713 Park Tank VFW Park N. College Street 238 Park Tank Hal Investments 10 Spring St 64 Park Tank Georgetown Hotels 600 San Gabriel Village 14 Park Tank Applebee's Int. 351 S IH Park Tank Rivery Towne Crossing Lp 1100 Rivery Blvd 34 Park Tank Duke's Smokehouse 408 W Morrow St 19 Park Tank Forbes Irrigation 1911 NE Inner Loop 110 Pecan Branch WWTP Clearwell Wms Co. Juvenile Justice Ctr SE Inner Loop 147 Pecan Branch WWTP Clearwell Southwestern Univ Non-Potable Irrigation 1107 N College St 2083 San Gabriel WWTP Clearwell Georgetown Football Field 107 Stadium Dr 76 San Gabriel WWTP Clearwell Baseball Fields & Park Irrigation 435 E Morrow St 25 San Gabriel WWTP Clearwell Non-Potable Irrigation / Park 443 E Morrow St 19 San Gabriel WWTP Clearwell Baseball Fields 521 E Morrow St 10 San Gabriel WWTP Clearwell McMaster Field 101 Walden Dr 337 San Gabriel WWTP Clearwell Rivery Towne Crossing Lp 698 S IH San Gabriel WWTP Clearwell 9th Grade Center Irrigation 2295 N Austin Ave 58 San Gabriel WWTP Clearwell Soccer Fields Irrigation 439 E Morrow St 27 San Gabriel WWTP Clearwell Note: Those demands in bold are existing customers. 6230

13 As in the existing condition, the Sun City Ponds will operate on a 2-day on, 1-day off irrigation scheme and will require constant inflow of 1,300 gpm. In addition to flow from the two ground water wells, the Pecan Branch WWTP (PBWWTP) line will be connected to this system to provide flow. PBWWTP can currently provide an average of 350 gpm (0.5 MGD) on a diurnal pattern. In the future, the plant will be expanded to 700 gpm (1.0 MGD), again provided on a diurnal pattern. This flow will reduce dependence on ground water. In the future, there is expected to be additional irrigation demand of 1,267 gpm as outlined in Table 5. Under existing conditions of average flow of 350 gpm provided by PBWWTP, the ground water wells will need to provide a constant 1,375 gpm. Under an expanded PBWWTP flow of 700 gpm on average, the ground water wells take can be reduced to a constant 1,050 gpm. In order to eliminate the use of ground water, the PBWWTP would have to be able to provide on average 1,725 gpm (2.5 MGD) of irrigation water. The Airport Tank is large enough to provide the necessary storage under all of these scenarios. However, there is not enough pumping capacity at the Airport Tank to meet the total demand of 2,567 gpm in the evenings. There is only enough capacity to fill the Sun City Ponds at a rate of 1,300 gpm over the entire day, but not enough capacity to provide enough water to meet the other irrigation demands of 1,267 gpm in the evening. In the future scenario, the Pecan Branch WWTP will be connected to the system to reduce the amount of ground water needed to meet irrigation demands. The plant will need to provide water to fill the Airport Tank, and meet irrigation demands of Forbes Irrigation and the Williamson County Juvenile Justice Center. Both of these potential future customers cannot be served from the Airport Tank. The demand from these two customers is 257 gpm in the evening irrigation hours. Considering the current average plant flow of 0.5 MGD and anticipated increased flow of 1.0 MGD, all of the water produced by the plant will effectively pass through the existing clearwell to fill the Airport Tank. Currently there is not a way to meet the demands of the two existing potable water customers who have a reasonable economic incentive to convert to irrigation water. In order to completely eliminate the need for ground water augmentation for the irrigation system and to meet the demands of these two customers would require an average flow of 1,825 gpm (2.6 MGD), storage capacity of approximately 120,000 gallons, and pumping capacity of about 2,200 gpm. In the future scenario, the Dove Springs WWTP (DSWWTP) will be connected to the irrigation distribution system and provide irrigation water. There are currently four potential customers, shown in Table 5, for a total demand of 651 gpm in the evening irrigation hours. To meet this demand, requires a constant inflow of 215 gpm over the entire day. The plant currently produces a flow of 700 gpm on average, so this need can easily be met, even considering that the flow is produced on a diurnal basis. However, this scenario would require just over 200,000 gallons of storage. The DSWWTP existing clearwell has a capacity of only 45,000 gallons. In addition, pumps capable of providing the 215 gpm would need to be installed. The existing flow produced is well above that necessary to meet the potential demands. In fact, the plant could potentially meet up to 2,150 gpm of irrigation demand in the evening hours 1,499 gpm above that required. This however would, require 800,000 gallons of storage and enough pumping capacity to move that amount of water into a GST and then out to distribution. 6231

14 CONCLUSIONS The Power of GIS Linked with Billing Record Data GIS tools allowed for geolocation of irrigation customers within the City. These locations were linked to billing records showing actual irrigation demand trends for the last several years. This allowed for geospatial distribution of customers into service areas allowing for analysis of demands on various sections of irrigation infrastructure. It should be noted that the last several years were relatively wet during the summer and likely do not represent a worst case scenario for irrigation demands. The City will consider periodic evaluation of billing records as they move forward with implementation of changes to the systems. What do the Economics Tell Us? The economic analysis for customers currently using potable water for irrigation purposes indicate that many customers could recover the cost for connecting to the irrigation distribution system within a reasonable timeframe. Out of the 45 potable irrigation customers considered, 28 of them would be able to recover the costs to connect to the irrigation system through savings within 10 years. Even considering the economic viability for the City to convert customers from potable to irrigation water, there are a number of instances where this would make sense. Comparing the cost to connect customers to the potential revenue generated from the sale of irrigation water, 11 of the 45 potential customers would be viable candidates considering a 20- year loan period at current rates. Potential Future Impacts Currently, about 245 MG (750 ac-ft) per year are provided through the irrigation system to meet irrigation needs. Over half of that existing irrigation demand supports one of the larger golf courses in the area that is provided ground water. Connecting in other WWTPs to the system will allow the City to reduce their use of ground water for irrigation purposes. The City of Georgetown s current potable water production is about 3 billion gallons annually. An additional 115 MG (350 ac-ft) of demand per year could be diverted to the irrigation system if customers who are considered economically viable were converted from the potable water system to the irrigation distribution system. This represents almost 4% of the current potable water production. These customer conversions could potentially represent long term savings in the ability to delay water treatment plant expansions and other distribution pumping, storage, and piping improvements. Implementation Considerations The City will need to consider if they want to take an aggressive approach to conversions and work to convert many or all of these customers at once. This would require more detailed evaluation of the economics to determine if additional charges might be needed. Another option would be to promote this concept to potential customers, encouraging them to make the conversion on their own timeline. In either instance, public education should be a considerable component of any program to convert customers to reclaimed irrigation water to facilitate a smooth transition to this resource. 6232