1. Deliberate tracer releases in Groundwater

2. Why deliberate tracer experiments?
Determine:
flow paths
residence times (< few years)
dispersion coefficients
reactive transport (e.g. push/pull)
presence of multiple phases (CO2 seq, oil, natural gas, air)

3. Borden aquifer Br-

4. Scale dependency of dispersivity

5. Push/pull experiments
Sedimentary aquifer fractured rock aquifer
Matter et al., 2006

6. Artificial recharge
Clark et al., 2005

7. Clark et al., 2005

8. Tracer release 900L of SF6 1L of 3He 8 days
Injection by bubbling through a diffusion stone that was placed in a water depth of about 1.2 m into pond #2.
Clark et al., 2005

9. Clark et al., 2005

10. Clark et al., 2005

11. Findings: Trapped air => excess air formation
Breakthrough curves of 3He and SF6 very similar => not much loss during recharge
maximum conc. was 25% of the mean pond concentration
~24 days residence time
50% recovery over 18 months
Clark et al., 2005

12. Winthrop landfill, ME
LANDFILL
As plume
50 meters
(horizontal)

13. Landfill History
1930 Dump operations begin including local industrial wastes
1972 Landfilling begins and serves adjacent towns
1979 Buried drums found at landfill
1982 Landfilling ceases
1987 Landfill cover system installed
1995 SVE and P&T remediation commences
N. Nikolaidis, UCon

16. 2 tracer experiments Is oxidation of the subsurface a viable option?
ORC (oxygen release compound, MgO2, REGENESIS)
single point injection tracer experiment (11/00)
flow direction,velocities
is treated water captured by EW2?
ORC injection experiment (1/01)
identification of zones influenced by ORC

17. Tracers
NaBr, NaCl, SF6
advantages of SF6: high dynamic range, extreme sensitivity (~1 fm/L), inert, conservative?

18. SF6 injection, 1st exp.

19. sampling

20. sampling 2nd exp.

21. American Museum of Natural History, 2001

22. SF6

23. N Existing well (5-10ft screen) New well (long screen) Extraction well
OW7
OW9
OW19
OW10
OW20
EW2
OW1 5’
OW8
OW12
OW13
OW16
OW18
OW17
OW14
OW11
OW6
OW15
P2-D
OW2 N
Existing well (5-10ft screen)
New well (long screen)
Extraction well
ORC injection point

24. Hydraulic head distribution
=> flow towards EW2
Harding, ESE

25. 1st tracer experiment 120 L of 5g/L NaCl salt solution
100,000 pptv SF6 (~5*10-7 moles total)
if equally distributed: 3 ppt

27. EW2, 1st tracer experiment
1/29/01

28. N Existing well (5-10ft screen) New well (long screen) Extraction well
OW7
OW9
OW19
OW10
OW20
EW2
OW1 5’
OW8
OW12
OW13
OW16
OW18
OW17
OW14
OW11
OW6
OW15
P2-D
OW2 N
Existing well (5-10ft screen)
New well (long screen)
Extraction well
ORC injection point

30. Sf6/Br comparison - OW12 L3 OW12 L 3 relative concentration
Relative time
=> average Sf6/Br ratio = 294ppt/(mg/L)
=> tracers behave similarly

31. Sf6/Br comparison - EW2 relative concentration Relative time
ppt/(mg/L)

33. Why was the recovery rate lower during the second experiment?

34. 1st tracer experiment
waste

35. 2nd tracer experiment
waste

36. OW12
OW11
OW14
OW13

37. Maximum SF6 concentrations measured at all levels, level at which
Maximum SF6
concentrations
measured at all
levels, level at which
it was measured
fence 49
4500,5 ?
4400,3
1400,1
7600,2
5500,2
840,2
10,3
After Harding ESE, Inc.,
hand drawn map by BKB, 10/26/00
MS, LDEO
Existing well (5-10ft screen)
New well (long screen)
Extraction well
ORC injection point
50,2 N
Approximate scale
20 feet
2/10/01

38. N Existing well (5-10ft screen) New well (long screen) Extraction well
OW7
OW9
OW19
OW10
OW20
EW2
OW1 5’
OW8
OW12
OW13
OW16
OW18
OW17
OW14
OW11
OW6
OW15
P2-D
OW2 N
Existing well (5-10ft screen)
New well (long screen)
Extraction well
ORC injection point

39. As concentrations => little change
Injection