In Situ Chemical Oxidation of VOCs and BTEX Plume in Low-Permeability SoilsAmit Haryani, PE, LSRP

Process Map

• Diesel, gasoline, solvents

Maintenance Yard

• Attain NJ GWQS - Rapidly

Client Goals

• Mixed plume in low perm soil

Challenges

• Benefits of real time CSM evolution

Evolution of CSM

Page 2

Process Map

• Low perm soils & MIP results

Thoughts on Data Interpretation

Evolution of

• Alternate oxidants

Evolution of Remedial Approach

Results & Path Forward

Page 3

Site History

2001

2002 -2005• Wells Installed• BTEX; MTBE;

TBA

2007 - 2008• Previous

COCs• PCE

Page 4

1998• 4,000g

Diesel UST• 2,000g

Diesel UST

2001• 10,000g Gas

UST• VOC Storage

Bldg• Fuel dispenser

TBA• Lead• TCE; cis-1,2-

DCE; VC• 1,2-DCA; 1,1-

DCE

Initial Conceptual Site Model – Hydrogeology

Asphalt

Brown to grey Silt + med to fine sand,

trace clay

10 ft

0.5 ft

2 ft, occasionally

Page 5

Dark grey clayey Silt

90 ft

Remedial Notions - Based on 2008 CSM

• Site geochemistry preferable for CHP• High dissolved iron content• Site pH is low (4-6) range

• Iron a catalyst for hydroxyl radical generation• Acidic pH assists keeping iron in solution & available for reaction• Site contaminants susceptible to immediate oxidation by CHP• Cons: potential TBA (as by-product MTBE oxidation) generation

CHP as remedial approach

• Cons: potential TBA (as by-product MTBE oxidation) generation

• Oxygen generated by hydrogen peroxide decomposition aids aerobic biological systems

• Site contaminants (TBA, MTBE, benzene, and VC) susceptible to long-term aerobic biological degradation

Plus, added benefits :

Page 6

Remedial Focus

• One saturated (8 – 13 ft bgs) soil sample• Groundwater• Sample from or adjacent to well with highest concentration (MW-10 @

MIP-6 and MIP-7)• Acidic buffer capacity / Peroxide reactivity / Oxidant effectiveness

EXTERNAL BENCH STUDY

BENCH RESULTS

2009

• Initial VOCs: gw 1.5 mg/L VOCs; soil 0.404 mg/kg• Soil pH

Recent History

2010

2011• SPS

Injections

Page 8

2009• Aug to Sep

- Peroxide Injections

• Nov – MIP / HPT

• Revise CSM

Phase I ISCO Application Summary

• Could not inject target volume (500 gal of 14% H2O2) due to surfacing.

• Reduced H2O2 from 14% to 8% to 4%.

• Eliminated addition of iron after IP-12.

Round 1 – August 20092009

• Used Hydraulic Profile Tool (HPT) on day 1 to establish permeable zones to target injections.

• Completed injections (IP 17 - 78) but at reduced target volume (120 gallons).

• Overall, actual volume

1800

3400

71

340

620

730

5400

270

2100

2200

610

1100

1300

1600

100

1000

10000

Tert Butyl Alcohol (TBA)

ppb

Phase I ISCO Results Summary

71

5.8

37

17

11

40

5

16

6.3

22

1

10

100

MW-1 MW-5 MW-6 MW-7 MW-10 MW-12 MW-102S MW-103S MW-105S MW-106S

Jan-08 Mar-09 Oct-09 Dec-09

Phase I ISCO Results Summary140 170

170

230

38

270

9.9

150

19

4248

350

13

85

100

680

140

12

80

140

35

57

47

420

11

80

10

48

100

1000

Methyl Tert Butyl Ether (MTBE)

ppb

3.2

3.8

9.9

1

6.2

8.5

6.4

0.93

2.8

4.9

10

0.1

1

10

MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW-105S MW-106S

Jan-08 Mar-09 Oct-09 Dec-09

Phase I ISCO Results Summary

71

780

61

450

37

110

980

61

210

690

40

100

1000

Pechloroethene (PCE)

ppb

1.4

2.7

4.5

5.3

1.2

16

5.3

4.6

5.3

1.6

1.4

14

18

1.1

4.3

6.7

1

10

MW-6 MW-8 MW-9 MW-10 MW-11 MW-12 MW-103S MW-105S MW-106S

Jan-08 Mar-09 Oct-09 Dec-09

Phase I ISCO Lessons Learned

• Poor performance > 7ft bgs.

Injection volumes restricted

• Injections forced to target 5 to 7 feet depth interval.

HPT data clarifies delivery issues.

Rapid reaction of Catalytic Hydrogen Peroxide

• Back pressure reduces ability to inject further oxidant solution.• Difficult to inject volumes into areas previously injected.

Rapid reaction of Catalytic Hydrogen Peroxide evolves gas = back pressure.

• Rebound / back diffusion?• Permanent injection wells?

Follow up treatment of residual “hot spots” warranted.

Phase II

• Strategy focusing on greatest residual• Use MIP/HPT direct sensing to focus “Hot Spot”

treatment efforts• Identify zones of flux

“Hot Spot” treatment

Apply different oxidant - SPS

2010

Page 14

• Strong oxidizing radical• Catalyzed by native iron• No temperature increase• No off-gas• Oxidation & reduced formation of TBA (suggested

in lit.) • More Persistent• Lower affinity for natural soil organics (Brown

2003); greater efficiency

MIP in Low Perm Soil

• PID readings >11 ft bgssuggestive of mg/L to 10s mg/L conc.?

• Signal in multiple areas of high soil conductivity

MIP Operator Observations

Multiple grab samples at depth do not confirmdepth do not confirm

• Others (Quinnan, et al) have documented bias in MIP within low permeability units

• + varying sensitivity depending on chlorine substitution

Signal Bias in Low Perm Soil

Phase II ISCO Application – January 2011

• 23 injection points• Catalyst – 575-gallon• 15% persulfate – 1,885-gallon• Flow Rate – 1 gpm – 3.57 gpm

Area 1

• 42 injection points• Catalyst – 1,710-gallon

Area 2

2011

• Catalyst – 1,710-gallon• 15% persulfate – 5,925-gallon• Flow Rate – 0.76 gpm – 3.85gpm

• 24 injection points• Catalyst – 600-gallon• 15% persulfate – 2,200-gallon• Flow Rate – 0.58 gpm – 2.78 gpm

Area 3

730

5400

37

270

2100

790

580

310

960

740

2002

90 380

48

340

1802

80

470

170

53

920

58

100

1000

10000

Phase II ISCO Results Summary - TBA

5.8

37

17

116.

2 7.7

6.5

12

7.2

1818

11

18

1

10

MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW-104S

MW-105S MW-106S

Mar-09 11-Mar 11-May 11-Aug

48

350

13

85

100

6.2

680

8.5

140

140

12

80

39 39

100

180

9.2

50

60

95

34

44

20

90

30

52

8.1

72

30

23

15

7.2

58

22

12

45

190

42

150

10

100

1000

Phase II ISCO Results Summary - MTBE

1.0

6.2 8

.5

2.7

1.8

1.7

5.6

4.7

0.7

4.8

8.1

7.2

0.56

0

1

10

MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S

Mar-09 11-Mar 11-May 11-Aug

110

980

56 61

99

200

51

67

81

210

48

95

170

46

80

97

100

1000

Phase II ISCO Results Summary - PCE

1.2

16

5.3

4.6 5.

3

1.1

1.1 1.

3

5

3.1

1.5

1.1 1.

3

1.3

3.5

6.6

2.3

1.7

2.4

1.6

2.6

15

1

10

MW-1 MW-5 MW-6 MW-7 MW-8 MW-9 MW-10 MW-11 MW-12 MW-102S MW-103S MW- 104SMW-105S MW-106S

Mar-09 11-Mar 11-May 11-Aug

Phase II ISCO Results Summary

• MW-5, MW-10, and MW-12

HOT spot wells = Significant reduction in concentrations

• Except: MW-1, MW-5, and MW-10

TBA below GWQS in all on-site wells

2011

• Except: MW-10

MTBE below GWQS in all on-site wells

• MW-104S and MW-106S

Off Site contaminant increases

Next Steps to Site Closure

• Past system behavior suggest anaerobic conditions exist(ed)• PCE degradation via RD with daughter products and ~50 %

reduction of COCs without active treatment over 4 yrs (‘04 – ’08)• In fuel release source areas, e-acceptors (e.g., oxygen, nitrate, iron

and sulfate) often absent/limited – handicapping biodegradation• Anerobic biodegradation systems benefit from Fe-SPS once redox

potential decreases again as the process supplements iron and sulfate

MNA Considerations – Anaerobic

Life Cycle Costs: MNA with LTM vs. Additional ISCO

• Given past plume stability (pre-ISCO perturbations), LTM could be in perpetuity

• One additional targeted applications of Fe-SPS equivalent to 2 years of LTM

• Additional ISCO shortens LTM time by years• Sequential injection events within target interval = mass reduction in

zones of flux.

Life Cycle Costs: MNA with LTM vs. Additional ISCO with Re-assessment

The End

Amit Haryani, PE, LSRPSenior Project Manager(732) 762-4275Amit.Haryani@aecom.com