1. In-Situ Remediation of Hexavalent Chromium, Antimony and
Nickel with Sub-Micron (Nano)-Scale Ferrous Sulfide Slurry
Jim V. Rouse, Richard H. Christensen, PhD LPG,
& Steven R. Irvin µg/L
(AcuityES, Fishers, IN)
© AcuityES 2013

2. Acuity Environmental Solutions
 Company’s Primary Focus:
• Environmental Liability Consulting (how to manage liabilities)
• Site Investigation – Soil, Groundwater, Air
• Remediation of contaminated Sites
• Expert Witness Testimony
 Company’s Secondary Focus:
• Environmental Permitting – Air, Water, Waste
• Environmental Compliance
© AcuityES 2013

3. In-Situ Remediation of Hexavalent Chromium,
Antimony and Nickel with Nano-Scale Ferrous
Sulfide Slurry
 Presented At:
• International Seminar on Remediation and Redevelopment of
Contaminated Sites, Sao Paulo, Brazil
• AEHS West Coast Conference, San Diego, CA
• USEPA’s Sustainable Remediation International Conference,
Amherst, MA
• AWPA National Conference, Ft. Lauderdale, FL & Nashville, TN
• Midwest States Environmental Consulting Assoc., Indianapolis, IN
• Battelle Conference, Monterey, California
© AcuityES 2013

4. Case Study In…
In Situ Geochemical Reduction
Stabilization (i.e., immobilizing) of metal constituents by
chemically reducing the metals of concern to less soluble forms
through the manipulation of geochemical factors such as:
• pH
• Oxidation potential (Eh or ORP)
• Complexation
• Sorption
• Ion exchange
Resulting in the elimination of metallic contaminants by:
• Precipitation
• Dissolution
• Oxidation
• Complexation
© AcuityES 2013

5. Key Project Considerations
Competitor’s Proposals for Project included:
• Off-site disposal of hazardous soils
• 15 - 20 year pump and treat remedy for groundwater
• >$8 Million
Note: original estimates based on >50% smaller source area
Our Solution:
• In Situ remediation of impacted soils and groundwater
• Goal: 2 year total remedy - 1/8th the time -
• Cost: $4.5 Million - Nearly 50% below competitor’s bids -
© AcuityES 2013

6. Chrome Plating
Gone Wild!
© AcuityES 2013

7. First things
first…
Segregation of Waste for Disposal
Interior Building Decontamination
Building Demolition
© AcuityES 2013

8. First things
first…
Groundwater Sampling
Soil Boring & Well Installation
Soil Sampling
© AcuityES 2013

9. Site Location -- Muncie, IN
GW
Impacts
Source
Areas
© AcuityES 2013

10. Site Plan for X-Section Line
Site Conditions
A’
First investigation – 2005
AcuityES - 2009
A
© AcuityES 2013

11. Geologic X-Section
FORMER
BASEMENT
SOURCE AREA
© AcuityES 2013

12. Hydrogeology
Unconfined Aquifer
Clay to 15 feet (w/stringers)
Sands & fine gravels
Static Water at 15’ bgl
Saturated thickness
5’ in SE to
> 25’ in NW
© AcuityES 2013

13. Soil Impacts
7,900 mg/Kg maximum Cr+6
3,600 mg/Kg Cr+6 at 12’ bgl
State Cleanup Goal - 38 mg/Kg
• Two Adjacent Source Areas
• 5,400 cubic yards of impact
• Perched water sand stringers
© AcuityES 2013

14. Groundwater
Impacts
On-Site
Cr+6
800,000 µg/L
9,700,000 µg/L
Groundwater COCs 66,000 sq ft (320 ft long) Plume
Cr+6, Sb, As, and Ni Offsite Cr+6 at 58,800 µg/L
State Cleanup Goal- 100 µg/L Cr+6
© AcuityES 2013

15. In Situ Chemical Reduction
BENCH TESTED CHEMICALS REDUCTANTS
•Ferrous Sulfate : FeSO4·7H2O •Sodium Thiosulfate : Na2S2O3
•Ferrous Sulfide : FeS •Sodium Metabisulfite : Na2S2O5
•Calcium Polysulfide (CPS) : CaSx •Sodium Sulfite : Na2SO3
•Zero Valent Iron
© AcuityES 2013

16. Selected Ferrous Sulfide (FeS)
FeS, Hybrid Form (aka precipitated pyrite)
Liquid suspension of 7% FeS
FeS, hybrid - With additional 2% free Sulfide
to simulate CaSx
Nanoscale: 98% crystals <5 microns
Cationic (Iron)
4 H2O + Cr042- + 3 Fe2- + 4 OH- 
3 Fe(OH)3+ Cr(OH)3 (Solid)
Anionic (sulfide)
17 H2O + 8 Cr042- + 3 HS- 
3 S + 8 Cr(OH)3 (Solid) + 12 OH-
© AcuityES 2013

17. In Situ Soil
Blending
GPS Grid Network – 10’ x 10’
(100’ x 70’ to 15’) & Shallow to 5’
Dual Axis Blender – 15’ Plunge
Total Area – 130’ x 110’
Computerized Dosing
© AcuityES 2013

18. In Situ Soil Blending
Dual Axis Blender
FeS injection/mixing
© AcuityES 2013

19. In Situ Soil Blending
Thorough Mixing to 15’ BGL
© AcuityES 2013

20. In Situ Soil Blending
Completed in 2 weeks
Total FeS = 78,300 gallons
Subsequent stabilization with aglime required
© AcuityES 2013

21. Confirmation Sampling
© AcuityES 2013

22. Groundwater Injections – FeS
THE NUMBERS
155 Inject Pts
15 ft ROI
6 wks complete
© AcuityES 2013

23. Groundwater Injections
Difficult
Injections
Boulder Fields
6’ caliche
(calcified silt)
Lodgement till
© AcuityES 2013

24. Groundwater
Injections
FeS Injection Totes
35,385 gallons injected
Rotosonic Drilling
Top Down Injection – 5ft intervals
© AcuityES 2013

25. Groundwater Injections
Sensitivity to
the Community
Required
Residential
Hours
© AcuityES 2013

26. Preferential Flow Paths
15 – 20’ bgl
Sand Unit
© AcuityES 2013

27. Preferential Flow Paths
20 - 25’ bgl
Sand Unit
© AcuityES 2013

28. Pre-Treatment Cr +6
State Cleanup
Goal of
100 µg/L
© AcuityES 2013

29. FeS Reductant Injection
© AcuityES 2013

30. 1 st Q Post-Treatment Cr +6
© AcuityES 2013

31. 2 nd Q Post-Treatment Cr +6
© AcuityES 2013

32. 3 rd Q Post-Treatment Cr +6
© AcuityES 2013

33. 1 st Supplemental Injection
© AcuityES 2013

34. 4 th Q Post-Treatment Cr +6
© AcuityES 2013

35. 5 th Q Post-Treatment Cr +6
© AcuityES 2013

36. 6 th Q Post-Treatment Cr +6
© AcuityES 2013

37. 7 th Q Post-Treatment Cr +6
© AcuityES 2013

38. 2 nd Supplemental Injection
© AcuityES 2013

39. 8 th – 10 th Q Post-Treatment Cr +6
© AcuityES 2013

40. Antimony Treatment
Antimony Concentrations:
Detected in 25 monitoring wells
on-Site up to 30,000 µg/L
off-Site up to 4,700 µg/L
State Industrial Cleanup level - 41 µg/L
State Residential Cleanup Level - 6 µg/L
Goal for Antimony:
Fixate onto Goethite (FeO(OH)) or
Precipitate as stibnite (Sb2S3)
© AcuityES 2013

41. Pre-Treatment Antimony
State Cleanup
Goal of
6 µg/L
© AcuityES 2013

42. FeS Reductant Injection
© AcuityES 2013

43. 1 st Q Post-Treatment Antimony
© AcuityES 2013

44. 2 nd Q Post-Treatment Antimony
© AcuityES 2013

45. 3 rd Q Post-Treatment Antimony
© AcuityES 2013

46. 1 st Supplemental Injection
© AcuityES 2013

47. 4 th - 10 th Q Post-Treatment Antimony
All results less
than method
detection level
of
6 µg/L
© AcuityES 2013

48. Nickel Treatment
Nickel Concentrations
Detected in 10 wells exceeding cleanup levels
off-Site up to 4,100 µg/L
on-Site up to 50,000 µg/L
State Industrial Cleanup level – 2,000 µg/L
State Residential Cleanup Level - 730 µg/L
Goal for Nickel:
Fixate as: westerveldite ([FeNiCo]As) or
pentlandite (FeNiS)
© AcuityES 2013

49. Pre-Treatment Nickel
State Cleanup
Goal of
730 µg/L
© AcuityES 2013

50. FeS Reductant Injection
© AcuityES 2013

51. 1st Q Post-Treatment Nickel
All results less
than method
detection level
of
50 µg/L
No
subsequent
detections
© AcuityES 2013

52. Arsenic
Arsenic – Pre-treatment As detected in 13 wells
@ concentrations of 11 µg/L to 360 µg/L
10th Quarter Sampling results:
only 2 wells @ 11 & 12 µg/L
Goal for Arsenic
Fixate as: orpiment (As2S3) or
arsenopyrite (FeAsS)
© AcuityES 2013

53. The Site Today
© AcuityES 2013

54. ISCR Benefits
1. In situ soil blending eliminated need for off-Site
hazardous waste disposal. (> 10,000 Tons)
2. In situ groundwater geochemical reduction
eliminated need for prolonged pump and treat.
3. In situ geochemical reduction reduced time
period of remediation from > 15 years to about 2
years.
© AcuityES 2013

55. CONTACT
Richard H. Christensen, PhD, LPG – rchristensen@acuityes.com
Steven R. Irvin – Irvin@acuityes.com
Jim V. Rouse – jrouse@acuityes.com
317-570-4919
Past Teaming Partners
CDM Smith Mundell & Associates
Burns & McDonnell CALIBRE
Professional Engineers MWH Global
Malcom Pirnie Carndo MMA
www.acuityes.com
© AcuityES 2013