Aquifer Recharge– Drinking Water Considerations –

Washington Department of HealthJune 19, 2013 Webinar

Chris PitreRebekah Weston

Managed Aquifer Recharge– the Right Tool in the Right Place –

• A water resource management tool.• Used around the world.• Ecology endorses ASR• Proponents are lining up in Washington.

WA DOH’s Role: Ensure protection of public health Facilitate between project proponents and Ecology

Why ASR in the PNW

• Water Availability– Water rights & winter water

• Financial– Capital infrastructure (storage) investment

• System reliability– Distribution of sources

• Environmental conditions– Climate change, fish 

DOH Interests in ASR• Protect public health.• Interact constructively with:

– Ecology• Water rights review• Policy/program development

– Project proponents• Show understanding of program components• Provide guidance

Walla Walla ASR Wellhead

Clogging

• System scale is a common concern.• Mitigate with pre‐recharge flushing of 

distribution system.

• Biofouling controlled by disinfection

• Filtered water (low TSS)  usually needed (though Walla Walla uses unfiltered water)

• Some clogging easily reversed by back flushing of well.

DISINFECTION BYPRODUCTS (DBPs)

• Disinfection needed to control biofouling, clogging.

• Inconsistency in regulations:– Drinking water standards (protection of public health, WAC 246‐290):

• Chloroform (TTHM) – 80 ppb• HAAs(5) – 60 ppb

– Groundwater protection standards (WAC 173‐200):

• Chloroform – 7 ppb

0.0

0.5

1.0

1.5

2.0

2.5

0

5

10

15

20

25

11/17/2000 12/2/2000 12/17/2000 1/1/2001 1/16/2001 1/31/2001 2/15/2001 3/2/2001

Res

idua

l Chl

orin

e (m

g/L)

Chl

orof

orm

and

Tot

al T

HM

(g/

L)

DateChloroform

Residual Chlorine

STORAGE(2 months)

RECHARGE(1 month)

RECOVERY(1.5 months)

Reco

vere

d V

olum

e =

Rech

arge

d

Chloroform WAC 173-200 Criteria (7 g/L)

Chlorination Disinfection Byproducts (DBPs)80 Residual Cl 

gone Natural AttenuationDBPs form whileResidual Cl is present

Drinking water 

standard

Yakima ASR Test

DBPs remain within safe drinking limits and naturally attenuate during storage

Protection of Groundwater Quality• Status Quo (Antidegradation Rule, WAC 173‐200)

– Passed in early days of environmental regulation development (~1980s)

– Stricter than drinking water standards

• Approaches to allow groundwater recharge :– Variance (needs renewal every 5‐year = project uncertainty)

Overriding Public Interest (OPI)– Groundwater Management Area (GWMA)

– Legislative fix

Oregon• Allows 50% of MCLs allowed (100% of SMCLs & DBPs)

• Agency discretion reserved

Burden on regulatory staffing resources.

Recommended

Source Approval for ASR is Different From Conventional Supply

Individual sources are generally stable.• Source (surface) water for recharge.• Groundwater storage.

Mixing of sources can be dynamic.• e.g., Redox reactions (e.g., oxidation of aquifer materials).

• Address with geochemical modeling, monitoring.

Reactions in the Aquifer

• Oxygenated recharge water+ reduced aquifer minerals

= Oxidation of sulfide minerals?• Potential release of trace elements (e.g., As)• Has happened in other areas (e.g., FL [Arsenic], WI [Cobalt])

• Mineral has to be accessible to recharged water(e.g., minerals locked in aquifer matrix is of less concern).

• Has not happened yet in the PNW.

Golder Associates ASR ProjectsVarious Stages of Operational Development

Studies

PortlandTigardTVWD

ClackamasSalemDallas

YakimaKennewickWalla Walla

Pendleton

Extents ofColumbia River Basalt

Groundwater Reactions

Recharge “bubble”

Reactions can:• Occur within bubble.• At interface (mixing zone).• Take time (kinetics).

Water Quality in RecoveryBreak Through Theory

0.0

0.2

0.4

0.6

0.8

1.00.0 0.1 1.0 10.0

C/Co

Volume Recovered/Volume Injected (-)Native Water

RechargedWater • Dispersivity (mixing) 

affects recovered water quality.

• Intrinsic to aquifer fabric

Sand

Fractured rock

0.0

0.2

0.4

0.6

0.8

1.00.0 0.1 1.0 10.0

C/Co

Volume Recovered/Volume Injected (-)

Fractured Chalk

Sandstone/Claystone

Fractured Sandstone

Sand & Gravel

Basalt

Native Water

Recharged Water

Water Quality in RecoveryMixing Examples

Basalt

Ellensburg Fm.

Data sets are from different projects and are affected by:  duration of storage; number of recharge/recovery cycles; and, other variables.  Examples illustrate the range of water quality distributions as a function of different aquifer fabrics.

Evaluation of Pilot Test Data – Yakima Example

C/C0 = 0.5SO4

TracersStorage Recovery

NO3

18OD

CFC‐12

Naturally occurring tracer data are used to evaluate the degree of mixing and hydrogeological characteristics (porous/fracture flow).

Example of Silica Dissolution Kinetics During Storage

Kennewick Willowbrook Well – Theoretical Pyrite Oxidation Simulation

O2

Fe

SO4

pH

Geochemical modeling is used to evaluate geochemical reactions during storage.

Testing the WatersMonitor water quality through full recharge/recovery cycle to evaluate potential reactions:1. Recharge (characterize input/baseline).2. Storage – long enough to see reactions (e.g., 2 mos).

3. Recovery – to get break through curve (e.g. 2 x recharge vol.)

• Analytical suite should include:– extended IOCs – DBPs – physical parameters

• Project specific considerations:– VOCs/SOCs– Radionuclides– Tracers

ASR & Operations (e.g., for Yakima)

Storage needed for fire flow

Conventional new storage: ~$2M

ASR (per well): ~$2M (1,000’ deep,

3,000 gpm) ~400 million gallons

ASR Costs• Conventional water costs:

– Water right: $1,000-$10,000/afy (water market)

– Seasonal storage: $5,000/af (Black Rock)

– Infrastructure storage: $2M (2 MG)

ASR costs: – Water right: Zero (using existing city rights)

– Seasonal storage: Zero (using Mother Nature’s aquifer)

– Infrastructure storage: $2M (per well)

Misconceptions About ASR

• How do we stop other people from taking the water we recharged? – CONTROLLED BY WATER RIGHTS – not an issue.

• The same molecule of water recharged has to be recovered. – NOT TRUE – Recovery is based on water balance accounting

ASR Water Quality RecapPre‐test analysis:• Mineralogical analysis.• Analysis of source and aquifer waters.• Geochemical modeling.

Recharge and recovery cycle analysis:• Sufficiently long storage period (e.g., 2 months).

• Obtain breakthrough curve (e.g., 2 x recharge volume).

Aquifer Recharge– Drinking Water Considerations –

Washington Department of HealthJune 19, 2013 Webinar

Chris PitreRebekah Weston

Thank you!