Attachment B
1.12 San Antonio Water System (SAWS) Recycled Water Program; Phased Expansion (L-21)
1.12.1 Description of Option
The San Antonio electric utility, City Public Service (CPS), has been using reclaimed wastewater for electric power generation for decades, and during the 1990s, the San Antonio Water System (SAWS) developed a Reuse Water Program[1],[2]. Construction of the San Antonio municipal water recycling system began in 1997. Phase I includes two main conveyance lines, with one line beginning at the Salado Creek Water Recycling Center (WRC) and extending north through the eastern part of the city, and the other beginning at the Leon Creek WRC and extending north through the western part of the city (Figure 1.12-1). Phase II of the Plan provides for interconnection of these two conveyance lines to allow east-west as well as north-south flow of recycled water. Subsequent expansion of the system may provide additional water supply to other parts of the city and Bexar County[3].
The present SAWS Recycled Water Program is capable of delivering
about 35,000 acft/yr, with estimated consumptive reuse of
24,941 acft/yr, which is included as existing water supply of the South
Central Texas Region. Recycled water is
used for non-potable purposes, including industrial purposes, office and
business cooling towers, landscape irrigation, and streamflow
augmentation. Such uses to date are
direct substitutes for water previously obtained from the Edwards Aquifer, and
thereby reduce the use of Edwards Aquifer water by the quantity of recycled
water used. This water supply option
involves the expansion of the recycled water program to provide dependable
water supplies for non-potable uses, bringing the total supply of recycled
water to a level sufficient to meet 20 percent of SAWS projected municipal
and industrial water demands.
Facilities for future expansion are expected to include southern
interconnections between the Leon Creek, Dos Rios, and Salado Creek WRCs as
well as a
northern interconnection linking the transmission lines originating at the Leon Creek and Salado Creek WRCs.
Figure 1.12-1. SAWS Water Recycling System
1.12.2 Water Availability
Increased treated wastewater volumes associated with increased municipal water use are potential sources of water to meet a part of the projected non-potable needs (shortages) of water user groups in the region. This reuse may be accomplished directly (prior to stream discharge or “flange-to-flange”) or indirectly through bed and banks delivery to downstream diversion and/or storage site(s) subject to applicable law. Direct and indirect reuse methods are both currently used by SAWS, however, it is most probable that direct reuse methods will be used in the expansion of the recycled water program. Indirect reuse of treated wastewater volumes derived from privately owned groundwater and/or interbasin transfer of surface water may be subject to fewer water rights or environmental flow constraints because these sources would not naturally have been present in the streams below wastewater treatment facilities.
For the purposes of consideration for inclusion in the South Central Texas Regional Water Plan, future expansion of the SAWS Recycled Water Program is based on the goal of meeting 20 percent of projected municipal and industrial water demands with recycled water. Table 1.12-1 summarizes the calculation of future quantities of recycled water potentially available after adjusting projected demands to account for recommended municipal water conservation projections for San Antonio (Section 1.1, Table 1.1-5, Vol. III). In addition, Table 1.12-1 includes estimates of projected effluent volumes likely to be discharged to the San Antonio River and/or tributary streams. These projected effluent volumes will be available for downstream water rights, reclamation through bed and banks transfer, and instream uses. Estimated recycled water quantities available through expansion of the SAWS system increase from 19,826 acft/yr in 2010 to 52,215 acft/yr in 2050.
1.12.3 Environmental Issues
As the ultimate configuration for a phased expansion of the SAWS Recycled Water Program has yet to be determined, this discussion of environmental issues focuses upon information developed for the planned system interconnections between the Leon Creek and Salado Creek WRCs and the Dos Rios WRC[4]. It is likely that further expansion of the water recycling system will encounter similar environmental issues and concerns to those encountered in the implementation of the existing system. Following a description of the project area, key issues including downstream flows, water quality, endangered species, and cultural resources are briefly discussed.
Table 1.12-1.
Estimated Potential Quantities of Recycled Water1
San Antonio Water System
|
|
2000 |
2010 |
2020 |
2030 |
2040 |
2050 |
|
Projected Demand |
|
|
|
|
|
|
|
Municipal |
220,405 |
242,339 |
272,507 |
312,695 |
349,957 |
391,640 |
|
Industrial |
16,805 |
19,682 |
22,359 |
24,935 |
28,264 |
31,697 |
|
Conservation (-) |
(29,610) |
(38,185) |
(36,477) |
(33,805) |
(35,710) |
(37,555) |
|
Net
Projected Demand2 |
207,600 |
223,836 |
258,389 |
303,825 |
342,511 |
385,782 |
|
Estimated
Total Effluent3 |
103,800 |
111,918 |
129,195 |
151,913 |
171,256 |
192,891 |
|
Current
Recycle Quantities4 |
24,941 |
24,941 |
24,941 |
24,941 |
24,941 |
24,941 |
|
Future Recycle Quantities |
|
19,826 |
26,737 |
35,824 |
43,561 |
52,215 |
|
Total Recycle Goal5 |
41,520 |
44,767 |
51,678 |
60,765 |
68,502 |
77,156 |
|
Remaining Effluent |
62,280 |
67,151 |
77,517 |
91,148 |
102,753 |
115,735 |
|
1. All quantities in acft/yr. 2. SAWS municipal demand plus Bexar County industrial demand less municipal water conservation projections for SAWS. 3. Calculated as 50 percent of Net Projected Demand. 4. Quantity shown is estimated consumptive use of recycled water. System capacity is about 35,000 acft/yr. 5. Calculated as 20 percent of Net Projected Demand. |
||||||
Expansion of the SAWS Recycled Water Program will occur within Bexar County which, in turn, lies within the Edwards Plateau (thin, rocky soils), Blackland Prairie (thick, clayey soils), and Rio Grande Plains (sandy soils) physiographic provinces. Geologic substrate includes sedimentary rock units such as limestones, sands, clays, and alluvium and terrace deposits. Bexar County is drained by tributaries of the Medina and San Antonio Rivers and underlain by the Edwards Aquifer from which San Antonio and San Pedro Springs periodically emanate. Flora and fauna of Bexar County are representative of the Edwards Plateau, Blackland Prairie, and South Texas Plains vegetation areas and the Balconian, Texan, and Tamaulipan biotic provinces. Urban and agricultural development within the county have had an influence on native terrestrial, riparian, and aquatic biota and have created cultural resources of historical, archaeological, and socio-economic importance.
As indicated in Table 1.12-1, treated effluent quantities in excess of those planned to be recycled are expected to increase throughout the 50-year planning horizon as a result of increasing water use and development of new water supplies from downstream, out-of-basin, and/or groundwater sources. Hence, downstream flows in the San Antonio River are expected to increase over time, potentially resulting in improved reliability of existing water rights, enhanced instream uses, and additional freshwater inflows to the Guadalupe Estuary. Maintenance of streamflows in excess of 55,000 acft/yr passing the gaging station on the San Antonio River near Falls City is not expected to be impaired by expansion of SAWS Recycled Water Program.
Applicable regulations define three classifications of recycled water based on the level of water quality as reflected in measurable parameters including BOD5, turbidity, and fecal coliform. SAWS expects to utilize only Type I recycled water which is of high quality and can be used in areas where the likelihood of public contact may be high. Non-food crops and landscaped areas may be irrigated using Type I recycled water without restriction, however, food crops so irrigated must be processed prior to human consumption. Water produced by the Salado, Leon, and Dos Rios Water Recycling Centers presently complies with the specified quality parameters for Type I recycled water.
Endangered species listed for Bexar County include the Black-capped Vireo, Golden-cheeked Warbler, two migratory birds, six arachnids, and three beetles (see Vol. III, Appendix D for additional information). Some care may be necessary should recycled water pipelines traverse preferred habit for the endemic species. Black-capped Vireos are insectivorous songbirds that nest in low shrubland thickets where vegetation extends to ground level. Golden-cheeked Warblers prefer habitat consisting of mature oak-juniper woodlands located along steep escarpments and canyons. The listed invertebrate species (arachnids and beetles) are all endemic to karst features or caves located in north and northwest Bexar County. The listed migratory bird species tend to avoid areas of concentrated human development.
Implementation of an expanded distribution system for recycled water will occur in predominantly urban areas and likely be concentrated in existing utility easements and previously disturbed floodplains. Hence, impacts to natural and cultural resources are expected to be minimal.
1.12.4 Engineering and Costing
Expansion of the SAWS Recycled Water Program could more than double the distribution capacity of the existing system during the next fifty years. Other than the planned southern interconnections of the water recycling centers (wastewater treatment facilities) and the northern interconnection of the existing distribution systems, specific elements of an expanded system are unknown at this time. Hence, estimates of cost for expansion of system capacity by 52,215 acft/yr by 2050 are based upon actual and projected costs for development of the existing 35,000 acft/yr system ($125,300,000[5]) plus estimated costs for the planned interconnections (Southern = $13,000,000 and Northern = $9,200,000[6]). Assuming debt service at an annual percentage rate of six percent for 30 years, the annual unit cost for development of the existing system is about $260 per acft. Applying this unit cost to the planned 52,215 acft/yr expansion of system capacity and adding estimated costs for the planned interconnections results in a Total Project Cost for expansion of the SAWS Recycled Water Program of about $209,231,000. Amortizing this Total Project Cost and accounting for estimated operations and maintenance and pumping energy costs results in an estimated Total Annual Cost of $20,617,000 and an Annual Unit Cost of Water of $395 per acft or $1.21 per 1000 gallons).
1.12.5 Implementation Issues
Implementation of an expanded SAWS Recycled Water Program (L-21) could directly affect the feasibility of other water supply options under consideration, including L‑11, L‑14, L‑20, S‑15D, S‑15E, S‑16C, and/or SCTN‑14b. However, since SAWS has successfully implemented the initial phases of its Recycled Water Program, there do not appear to be major implementation issues to overcome.