Aquifer Storage and Recovery Challenges and Solutions Frederick Bloetscher, Ph.D., P.E. Florida Atlantic University

Transcription

1 Aquifer Storage and Recovery Challenges and Solutions Frederick Bloetscher, Ph.D., P.E. Florida Atlantic University

2 Why Pursue ASR? Store water for Future Raw water Potable water Irrigation Fire/other Blend water for quality purposes Water quality improvements

3 DEPTH (Feet Below Land Surface) ASR Concept TREATMENT PLANT ASR WELL DURING INJECTION ASR WELL DURING RECOVERY LAND SURFACE 0 WATER TABLE AQUIFER CONFINING BED CONFINING BEDS CONFINED SYSTEM 600 MIXING ZONE INJECTED POTABLE WATER

4 What the wellhead looks like

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8 Number of ASR Well Sites Where is ASR being implemented? FL CA NJ AZ OR SC WA CO TX NV IA UT DE GA ID KS NC NY VA WI WY IL MN NM OK SD TN State

9 100 Well Sites by decade s 1970s 1980s 1990s 2000s post 2010

10 So you want to know more.. Water Source Well construction Aquifer formation Operations Equipment Issues that can arise

11 Typical sources of water Surface Water, 129, 64% Other, 1, 1% Reclaimed, 28, 14% Ground Water, 43, 21%

12 Reported uses of recovered water Canal Recharge, 2, 1% Potable Supply, 108, 53% Raw, 52, 26% Fire, 2, 1% Cooling Water, 3, 1% Irrigation, 37, 18%

13 Typical types of casing material Steel, 120, 77% Fiberglass, 3, 2% PVC, 32, 20% Stainless Steel, 2, 1%

14 Well Construction

15 Column Pipe Inner casing Outer casing Surficial Formation Confinement Intermediate Casing Confinement Submersible Pump Screen Injection Horizon

16 Relative frequency Casing Diameter Casing Diam.

17 Relative frequency Relative frequency Typical well depths Depth of casing Depth of well

18 Formation - storage zone lithology Basalt Carbonate 8% 1% Alluvial 33% Limestone 33% Sandstone 11% Granite 0% Sand / Clay 6% Sandstone 8%

19 Lithology of confinement Clay 34% Limestone 14% Granite 3% Silt / Basalt 8% Shale 6% None 3% Alluvial 1% Basalt / Clay 16% Dolomite 15%

20 Relative frequency Relative frequency Injection Horizon Thickness Injection Horizon Injection Horizon

21 Relative frequency TDS TDS

22 Relative Frequency Transmissivity Transmissivity (gpd/sf)

23 Relative frequency Operations- Injection rate of wells (MGD) injection Capacity (MGD)

24 Relative frequency Rate of Recovery of Injected Water (MGD) Withdrawal Capacity (MGD)

25 Relative frequency Ratio (In:out) Ratio Injection to Withdrawal

26 Data Collection Number of cycles per site 5 to 10 11% 2 to 5 43% 10 to 20 26% 0 to 1 9% > 20 11%

27 Relative frequency Water stored (millions of gallons) 0.8 Histogram (Amount of Water Stored (MG)) Amount of Water Stored (MG)

28 Relative frequency ASR recovery rates for the ASR sites (MGD) Source: Reese, USGS Peak Flow on Site (MGD)

29 Records Drawdown Pump Rate Power Use Specific Capacity Water Quality (temperature, conductivity, ORP, silt density index, ph, ions before and after injection, metals)

30 Growth By Decade

31 Location of ASR Wells with Time

32 Source Water with Time

33 Water Use with Time

34 Injection Formation with Time

35 Status with Time

36 Challenges Encountered

37 Challenges 1. Prohibition (GA reintroduced in 2015) 2. Thm regulation issues (potable and reuse water have chlorine) 3. Water rights after injection who s water? 4. Storage time (how long - 6 mo? 1 mo? 3 yrs?) 5. Recovery what % is acceptable (20? 40? 70?) 6. Metals mobilization (FL, WI, others) 7. Clogging (just like any well, but injection accelerates it) 8. Expectations of clients (cheap, fast, high recovery, no treatment)

38 Georgia In 1996, TSG (The Savannah Group Water Services) a water supply company, applied for three surface water withdrawal permits Georgia Legislature enacted a moratorium on ASR in 1999 for 11 coastal counties, effectively ending the TSG proposal. The moratorium expired in 2014 Georgia Regional Commission (SWGRC) submitted a Governor s Water Supply Program (GWSP) application for a $13.5 million experimental large flow augmentation program for the Flint River project

39 Georgia Starting in the fall of 2014, discussion about extending the ban on ASR developed. Senate bill 36 was introduced to require the Board of Natural Resources to adopt regulations that provide for the protection and preservation of the Floridan aquifer No companion in the Senate House Study Committee on Saltwater Intrusion into Coastal Aquifers, but the directive does not include the SB 36 language. More to come

40 Florida Water must meet Florida s drinking water standards prior to injection into an ASR well Water quality changes include arsenic and other metals mobilization. Arsenic mobilization in limestone was reported in Florida wells The arsenic issue in Florida did not affect many sites until 2005, when the federal drinking water standard for arsenic was reduced from 50 ug/l to 10 ug/l.

41 Florida The Florida ASR wells with levels of arsenic above the 2005 standard all use the same Floridan limestone formation. Oxygenated water can release naturally-occurring arsenic from underground limestone formations and raise arsenic levels In 2012, the Florida Department of Environmental Protection (DEP) sought a regulatory approach that would allow the use of ASR while addressing the drinking water standards.

42 Solution Zone-of-discharge Preventing the endangerment of adjacent underground drinking water sources through monitoring Preventing public access to that portion of the aquifer by ensuring that the operator of the facility owns or otherwise controls the installation of wells within the property overlying the zone of discharge FDEP may reach the necessary non-endangerment finding

43 Zone of Discharge Defined in the regulation as a volume underlying or surrounding the site and extending to the base of a specifically designated aquifer or aquifers, within which an opportunity for the treatment, mixture or dispersion of wastes into receiving ground water is afforded.

44 Results EPA agreed DEP issued permits for Tampa Rome, Destin Reuse, Bradenton, Punta Gorda, Naples, Lee County Corkscrew, Peace River and Sarasota County Central WRF ASR wells Orange County, Collier Livingston Road, West Palm Beach, Sanford all active

45 Challenge Solutions Wells will likely need to be treated to deal with clogging Treatment may be required for metals, ORP Wells need extended testing and multiple cycles with large injection and storage times Recovery may be adjusted by adjusting withdrawal rates

46 CERP ASR

47 CERP ASR

48 Source: ACOE Treatment may be Extensive

49 Recovery Time is Relevant Injection zone water quality matters

50 Recovery with Time?

51 In Short, Expectations Not always fast Not always cheap Not always high recovery May need treatment May need more wells than you think But these are issue to deal with as the project evolves!

52 Summary ASR an be a useful tool to help manage water supplies, but manage expectations The type of formation, its transmissivity, and confinement are the major issues for quick, less cost projects Clogging is an ongoing issue with all water, but esp raw surface water and reclaimed water Success is not a short term issue

53 Questions?