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WADOH Webinar 2013-06-19
- 2. 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
- 3. 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
- 4. 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
- 5. 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.
- 6. 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
- 7. 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 ResidualChlorine(mg/L) ChloroformandTotalTHM(g/L) Date Chloroform Residual Chlorine STORAGE (2 months) RECHARGE (1 month) RECOVERY (1.5 months) RecoveredVolume =Recharged Chloroform WAC 173-200 Criteria (7 g/L) Chlorination Disinfection Byproducts (DBPs) 80 Residual Cl gone Natural Attenuation DBPs form while Residual Cl is present Drinking water standard Yakima ASR Test DBPs remain within safe drinking limits and naturally attenuate during storage
- 8. 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
- 9. 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.
- 10. 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.
- 12. Groundwater Reactions Recharge “bubble” Reactions can: • Occur within bubble. • At interface (mixing zone). • Take time (kinetics).
- 13. Water Quality in Recovery Break Through Theory 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.1 1.0 10.0 C/Co Volume Recovered/Volume Injected (-)Native Water Recharged Water • Dispersivity (mixing) affects recovered water quality. • Intrinsic to aquifer fabric Sand Fractured rock
- 14. 0.0 0.2 0.4 0.6 0.8 1.0 0.0 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 Recovery Mixing 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.
- 15. Evaluation of Pilot Test Data – Yakima Example C/C0 = 0.5 SO4 Tracers Storage Recovery NO3 18O D CFC‐12 Naturally occurring tracer data are used to evaluate the degree of mixing and hydrogeological characteristics (porous/fracture flow).
- 18. Testing the Waters Monitor 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
- 19. 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
- 20. 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)
- 21. 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
- 22. ASR Water Quality Recap Pre‐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).