Presented by:

Kevin J. Spencer, P.G.

R.W. Harden and Associates, Inc.

Benefits and Challenges of

Developing Brackish Groundwater Supplies

WATER

Supply

ObjectivesObjectives

• The Need to Develop Brackish The Need to Develop Brackish Groundwater SuppliesGroundwater Supplies

• Potential AdvantagesPotential Advantages

• Practical ConsiderationsPractical Considerations

•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

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

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

Alternative SourcesAlternative Sources

•ConservationConservation

•ReuseReuse

•DesalinationDesalination– Sea Water Sea Water – Brackish Brackish

GroundwaterGroundwater

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

$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

• 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

• 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

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

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

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

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

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)

Implementation ChallengesImplementation Challenges

• Proving up the supplyProving up the supply

• Concentrate DisposalConcentrate Disposal

• Well Design ConsiderationsWell Design Considerations

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

Concentrate DisposalConcentrate Disposal

• Discharge to brackish surface Discharge to brackish surface waterwater

• Discharge to oceanDischarge to ocean

• InjectionInjection

• Waste water systemsWaste water systems

• EvaporativeEvaporative

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

• 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

•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

Questions?Questions?