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Presented by:
Kevin J. Spencer, P.G.
R.W. Harden and Associates, Inc.
Benefits and Challenges of
Developing Brackish Groundwater Supplies
WATER
Supply
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ObjectivesObjectives
• The Need to Develop Brackish The Need to Develop Brackish Groundwater SuppliesGroundwater Supplies
• Potential AdvantagesPotential Advantages
• Practical ConsiderationsPractical Considerations
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•City of Los Fresnos
•Indian Lake
•Port of BrownsvilleValley MUD #2
Rio Grande Regional Water Planning GroupRio Grande Regional Water Planning GroupSouthmost Regional Water Authority
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Surface Reservoir ConditionsSurface Reservoir Conditions
Summer 2002 – 25% Capacity
Water Level at 50% Capacity
Water Level at 100% Capacity
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
Acre Feet in Millions
Reservoir Capacity
Water Levels Amistad andFalcon Reservoirs (U.S.Ownership)
Source: TNRCC Watermaster
3.3
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What Can We Expect?What Can We Expect?• Increased Increased
demand/less waterdemand/less water• Implementation of Implementation of
drought management drought management strategiesstrategies
• Irrigation shortagesIrrigation shortages– ““Piggy Back” by Piggy Back” by
municipalitiesmunicipalities– Hydrilla/ Hyacinth Hydrilla/ Hyacinth
blockageblockage
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Alternative SourcesAlternative Sources
•ConservationConservation
•ReuseReuse
•DesalinationDesalination– Sea Water Sea Water – Brackish Brackish
GroundwaterGroundwater
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Brackish Groundwater DesalinationBrackish Groundwater Desalination
• Significant brackish Significant brackish groundwater reserves in Gulf groundwater reserves in Gulf Coast aquifersCoast aquifers
• Independent of river flowsIndependent of river flows
• Not subject to water rights Not subject to water rights purchases*purchases*
• Cost of treatment comparable Cost of treatment comparable to surface waterto surface water
• Improved water qualityImproved water quality
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$0
$1
$2
$3
$4
$5
$6
$7
1980 1985 1990 1995 2000 2005 2010
Surface
Brackish
Sea Water
Cost TrendsCost Trends
Cost per 1000 gallon including debt service and operations
Source: NRS Consulting Engineers
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• Degree of total dissolved solids Degree of total dissolved solids
• Power costsPower costs
• Economies of scaleEconomies of scale
• LocationLocation
• Concentrate disposalConcentrate disposal
Cost FactorsCost Factors
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• Advantages over sea waterAdvantages over sea water– Significant reduction in plant Significant reduction in plant
capital and O&Mcapital and O&M– Reduced environmental impactReduced environmental impact
• Advantages over surface waterAdvantages over surface water– Drought tolerantDrought tolerant– Improved water qualityImproved water quality– Water rights savingsWater rights savings
Brackish GroundwaterBrackish Groundwater
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Brackish GroundwaterBrackish Groundwater
• Advantages over fresh Advantages over fresh groundwatergroundwater– New Supply Resource New Supply Resource – Less CompetitionLess Competition– Less RegulationLess Regulation– Positive Public PerceptionPositive Public Perception
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Regional Water SupplyRegional Water Supply
• Establish economies of scaleEstablish economies of scale
• Favorable to funding agenciesFavorable to funding agencies– Texas Water Development Texas Water Development
Board policy statement Board policy statement – Infrastructure financingInfrastructure financing
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PUB92.9%
Indian Lake0.2%
VMUD2.5%
Los Fresnos2.3%
BND2.1%
Allocation of WaterAllocation of Water
7.5 MGD Phase ISouthmost Regional Water Authority
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Annual Availability
from Authority
43%
Remaining Supply from Participant
57%
Capacity ProvidedCapacity Provided
Southmost Regional Water Authority
Total Water Sales 6,316,998,573
Annual Availability from Authority 2,737,500,000
Remaining Supply from Participant 3,579,498,573
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Planned Planned BrackishBrackish GW Projects GW Projects
• North Alamo WSC (5-10 MGD)North Alamo WSC (5-10 MGD)
• City of Edinburg (5 MGD)City of Edinburg (5 MGD)
• City of Raymondville (~2 MGD)City of Raymondville (~2 MGD)
• City of Combs (~0.5 MGD)City of Combs (~0.5 MGD)
• Laguna Madre WD (2-3 MGD)Laguna Madre WD (2-3 MGD)
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Implementation ChallengesImplementation Challenges
• Proving up the supplyProving up the supply
• Concentrate DisposalConcentrate Disposal
• Well Design ConsiderationsWell Design Considerations
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Proving Up the SupplyProving Up the Supply
• Initial ModelingInitial Modeling
• Test DrillingTest Drilling
• Development of Geologic Development of Geologic FrameworkFramework
• Long-Term Aquifer TestingLong-Term Aquifer Testing
• Refinement of the ModelRefinement of the Model
• Locating Suitable Well SitesLocating Suitable Well Sites
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Concentrate DisposalConcentrate Disposal
• Discharge to brackish surface Discharge to brackish surface waterwater
• Discharge to oceanDischarge to ocean
• InjectionInjection
• Waste water systemsWaste water systems
• EvaporativeEvaporative
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Well Design ConsiderationsWell Design Considerations• Corrosion ProtectionCorrosion Protection• Casing DesignCasing Design
– Stainless SteelStainless Steel– PVCPVC– Carbon SteelCarbon Steel– FiberglassFiberglass– CoatingsCoatings
• Pump Column DesignPump Column Design– Stainless SteelStainless Steel– PVCPVC– FiberglassFiberglass
• Pump Construction MaterialsPump Construction Materials– Bowls and Motors - Stainless SteelBowls and Motors - Stainless Steel– Impellers - Brass/Stainless Steel/Ceramic Impellers - Brass/Stainless Steel/Ceramic
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• Brackish groundwater is the Brackish groundwater is the least cost alternative for each least cost alternative for each entityentity
• Regional AdvantagesRegional Advantages– Economy of ScaleEconomy of Scale– Personnel cost savingsPersonnel cost savings– Common well fieldCommon well field– Potential for additional Potential for additional
partnerspartners– Favorable grant potentialFavorable grant potential
Summary and ConclusionsSummary and Conclusions
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•Cost FactorsCost Factors– Improvement in Membrane Improvement in Membrane
TechnologyTechnology– Operation of RO at peak capacityOperation of RO at peak capacity– Increasing expense of surface Increasing expense of surface
water treatment and water water treatment and water rightsrights
•Water Quality ImprovementWater Quality Improvement•Decreased CompetitionDecreased Competition
Summary and ConclusionsSummary and Conclusions
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Questions?Questions?