Benefits and Challenges of Developing Brackish Groundwater Supplies

1. WATER Supply Benefits and Challenges of Developing Brackish Groundwater Supplies Presented by: Kevin J. Spencer, P.G. R.W. Harden and Associates, Inc.

2. Objectives • The Need to Develop Brackish Groundwater Supplies • Potential Advantages • Practical Considerations

3. Rio Grande Regional Water Planning Group Southmost Regional Water Authority Valley MUD #2 • City of Los Fresnos • Indian Lake • Port of Brownsville

4. Water Levels Amistad and Falcon Reservoirs (U.S.Ownership) Acre Feet in Millions Reservoir Capacity 4.0 3.5 Water Level at 100% Capacity 3.3 3.0 2.5 2.0 Water Level at 50% Capacity 1.5 1.0 Summer 2002 – 25% Capacity 0.5 Source: TNRCC Watermaster Surface Reservoir Conditions

9. What Can We Expect? • Increased demand/less water • Implementation of drought management strategies • Irrigation shortages • “Piggy Back” by municipalities • Hydrilla/ Hyacinth blockage

10. Alternative Sources • Conservation • Reuse • Desalination • Sea Water • Brackish Groundwater

11. Brackish Groundwater Desalination • Significant brackish groundwater reserves in Gulf Coast aquifers • Independent of river flows • Not subject to water rights purchases* • Cost of treatment comparable to surface water • Improved water quality

12. Cost Trends Cost per 1000 gallon including debt service and operations Source: NRS Consulting Engineers

13. Cost Factors • Degree of total dissolved solids • Power costs • Economies of scale • Location • Concentrate disposal

14. Brackish Groundwater • Advantages over sea water • Significant reduction in plant capital and O&M • Reduced environmental impact • Advantages over surface water • Drought tolerant • Improved water quality • Water rights savings

15. Brackish Groundwater • Advantages over fresh groundwater • New Supply Resource • Less Competition • Less Regulation • Positive Public Perception

16. Regional Water Supply • Establish economies of scale • Favorable to funding agencies • Texas Water Development Board policy statement • Infrastructure financing

17. Southmost Regional Water Authority Allocation of Water 7.5 MGD Phase I

18. Southmost Regional Water Authority Capacity Provided

19. Planned Brackish GW Projects • North Alamo WSC (5-10 MGD) • City of Edinburg (5 MGD) • City of Raymondville (~2 MGD) • City of Combs (~0.5 MGD) • Laguna Madre WD (2-3 MGD)

20. Implementation Challenges • Proving up the supply • Concentrate Disposal • Well Design Considerations

21. Proving Up the Supply • Initial Modeling • Test Drilling • Development of Geologic Framework • Long-Term Aquifer Testing • Refinement of the Model • Locating Suitable Well Sites

22. Concentrate Disposal • Discharge to brackish surface water • Discharge to ocean • Injection • Waste water systems • Evaporative

23. Well Design Considerations • Corrosion Protection • Casing Design • Stainless Steel • PVC • Carbon Steel • Fiberglass • Coatings • Pump Column Design • Stainless Steel • PVC • Fiberglass • Pump Construction Materials • Bowls and Motors - Stainless Steel • Impellers - Brass/Stainless Steel/Ceramic

24. Summary and Conclusions • Brackish groundwater is the least cost alternative for each entity • Regional Advantages • Economy of Scale • Personnel cost savings • Common well field • Potential for additional partners • Favorable grant potential

25. Summary and Conclusions • Cost Factors • Improvement in Membrane Technology • Operation of RO at peak capacity • Increasing expense of surface water treatment and water rights • Water Quality Improvement • Decreased Competition

26. Questions?