LNAPL CONCEPTUAL SITE MODEL & MINIMIZING REBOUND WHEN APPLYING IN- SITU CHEMICAL TREATMENT

Transcription

1 LNAPL CONCEPTUAL SITE MODEL & MINIMIZING REBOUND WHEN APPLYING IN- SITU CHEMICAL TREATMENT Rick Ahlers, PE & Jeff McDonough, PE May 4, 2017

2 Agenda LNAPL Science What Happens When LNAPL Is Released? The LNAPL Conceptual Site Model What Should We Know? The LNAPL Conceptual Site Model What Should We Do? Alternatives to LNAPL Removal Phase Change ISCO What Causes Rebound? Other Phase Change Alternatives 2

3 Introduction What s wrong with the old approach to LNAPL? What s a better approach?

4 New Observation No New Observation Old Approach to Assessing LNAPL Risk High Recovery Low Recovery LNAPL ("Free Product ) Risk 4

5 New Observation No New Observation Old Approach to Assessing LNAPL Risk High Recovery Low Recovery LNAPL ("Free Product ) Risk Dissolved Risk 5

6 New Observation No New Observation Old Approach to Assessing LNAPL Risk High Recovery Low Recovery LNAPL ("Free Product ) Risk Dissolved Risk Risk = LNAPL Thickness in Wells, then Dissolved (if still present) 6

7 New Risk-Based LNAPL Management Approach Unstable LNAPL LNAPL Migration & Composition Risk 7

8 New Risk-Based LNAPL Management Approach Unstable LNAPL Stable LNAPL Residual LNAPL LNAPL Migration & Composition Risk LNAPL Composition Risk Only 8

9 New Risk-Based LNAPL Management Approach Unstable LNAPL Stable LNAPL Residual LNAPL LNAPL Migration & Composition Risk LNAPL Composition Risk Only Risk = LNAPL Instability + LNAPL Composition 9

10 What About Free Product Removal to MEP*? Stable LNAPL Initial Mass > Final Mass Initial Thickness Final Thickness * Maximum Extent Practicable 10

11 What About Free Product Removal to MEP*? Stable LNAPL * Maximum Extent Practicable Initial Mass > Final Mass Initial Thickness Final Thickness Initial Mass Final Mass Initial Thickness >> Final Thickness 11

12 What About Free Product Removal to MEP*? Stable LNAPL * Maximum Extent Practicable Initial Mass > Final Mass Initial Thickness Final Thickness Initial Mass Final Mass Initial Thickness >> Final Thickness Key Question: Will LNAPL Recovery Significantly Change LNAPL Mass? 12

13 How To Avoid Ineffective LNAPL Recovery Stable LNAPL Risk-Based LNAPL Management LNAPL Stability LNAPL Recoverability Natural Source Zone Depletion LNAPL Composition Risk 13

14 Evolution of an LNAPL Site: The Basic Science

15 LNAPL Saturation What Happens When LNAPL is Released? Time 1 Time 2 Hi LNAPL Head Time 3 Time 4 Soil pore resistance Buoyancy Lo 15

16 Stable LNAPL Distribution Vadose Zone Soil grain Water Air Capillary Zone LNAPL Saturated Zone Key Point: LNAPL shares the pores with groundwater and soil vapor 16

17 Three-Phase Behavior (Vadose Zone) NAPL migration through homogeneous vadose zone NAPL migration through heterogeneous vadose zone Air Water NAPL NAPL is intermediate wetting phase NAPL NAPL is drawn into finer grained soil by capillary tension (imbibition) Mayer & Hassanizadeh 2005 Soil and Groundwater Contamination: Nonaqueous Phase Liquids AGU 17

18 Relative Permeability Reduces effective permeability to both water and LNAPL (k rw ) Saturated Zone example S n = 15% k rn = 002 S w = 85% k rw = 026 Water Saturation (S w ) NAPL Saturation (S n ) 18

19 Elevation LNAPL Smearing 1 s n 0 1 s n 0 1 s n 0 1 s n 0 1 s n s w residual water low 3- phase residual LNAPL saturation 0 1 s w low 3- phase residual LNAPL saturation higher 2- phase residual LNAPL saturation 0 1 s w 0 LNAPL immobile higher 2- phase residual LNAPL saturation residual water low 3-phase residual LNAPL saturation s w s w After Chevron 1996 Traps LNAPL above and below the mobile LNAPL interval 09 May

20 LNAPL LNAPL Mobility & Water Table Fluctuation 1 s n 0 residual water low 3- phase residual LNAPL saturation 0 1 s w Low Water Harmon et al, Colorado State University 20

21 LNAPL LNAPL Mobility & Water Table Fluctuation 1 s n 0 Subsequent High Water k rn > 0 k rw < 1 low 3- phase residual LNAPL saturation higher 2- phase residual LNAPL saturation k rn = 0 k rw < s w Harmon et al, Colorado State University 21

22 (Mobile) LNAPL Stabilized & Diminished by NSZD T n i n NSZD = Dist LNAPL flow toward edges of body is balanced (or overwhelmed) by natural losses 22

23 NSZD Stabilizes & Diminishes Mobile & Residual LNAPL Think of the LNAPL body as a glacier 23

24 The LNAPL Conceptual Site Model (LCSM): The Backbone of a Robust Response

25 What Is An LCSM? LCSM Vapor Phase CSM LNAPL LCSM Dissolved Phase ITRC 2009 LNAPL Conceptual Site Model 25

26 New Site: Initial Investigation Old Site: Review No Further Action LCSM & Alternative Evaluation Initial CSM/LCSM Remedy/Control LCSM Design & Performance LCSM LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Design Remedy/Control; Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Alternative Evaluation Yes Yes Yes No CSM/LCSM Sufficient to Determine Concerns? Yes Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? LCSM Sufficient to Design Remedy/Control & Select Objective(s) & Metric(s)? Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 26

27 New Site: Initial Investigation Old Site: Review No Further Action The Wrong Way Initial CSM/LCSM Remedy/Control LCSM Performance LCSM This is a really simple site LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Yes Alternative Evaluation No CSM/LCSM Sufficient to Determine Concerns? Yes I ve worked on many sites I know what I m doing Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? Yes LCSM Sufficient to Select Objective(s) & Metric(s)? Yes Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 27

28 National Backlog Slowing Trend of Backlog Reduction EPA 2016 Semiannual Report Of UST Performance Measures, End Of Fiscal Year 2016 (October 1, 2015 September 30, 2016) Office of Underground Storage Tanks November 28

29 Balance Tipping to Older Open Cases EPA 2011 The National LUST Cleanup Backlog: A Study of Opportunities September 29

30 Closure of Complex (Groundwater) Sites Lags Proportion of Complex Sites EPA 2011 The National LUST Cleanup Backlog: A Study of Opportunities September 30

31 Remediation of LNAPL in Groundwater is Complicated Groundwater Concentration Half Life (yr) Benzene MTBE TBA Natural Depletion Only LNAPL Recovery Only Groundwater Remedy Only Groundwater Remedy + NAPL Recovery R Kamath, J A Connor, T E McHugh, A Nemir, M P Le, and A J Ryan Use of Long-Term Monitoring Data to Evaluate Benzene, MTBE, and TBA Plume Behavior in Groundwater at Retail Gasoline Sites J Environ Eng, 2012, 138(4):

32 Building an LNAPL Conceptual Site Model: An Iterative Approach

33 New Site: Initial Investigation Old Site: Review No Further Action 1 Initial LCSM & Concerns Initial CSM/LCSM Remedy/Control LCSM Design & Performance LCSM LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Design Remedy/Control; Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Alternative Evaluation Yes Yes Yes No CSM/LCSM Sufficient to Determine Concerns? Yes Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? LCSM Sufficient to Design Remedy/Control & Select Objective(s) & Metric(s)? Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 33

34 Initial LCSM Questions Is the LNAPL body (source zone) delineated horizontally and vertically? Is the LNAPL body stable, ie, is the total LNAPL footprint not expanding? How does stratigraphy relate to LNAPL distribution and potential migration? Does the potential for preferential pathways exist? Is there LNAPL in wells? Is the LNAPL recoverable? Are dissolved or vapor issues expected based on LNAPL composition? Are dissolved and/or vapor plumes characterized? Do soil, soil vapor, or groundwater exceed criteria? Are receptors pathways complete or incomplete? 34

35 LNAPL Concerns Utility corridor/ drain Drinking water well LNAPL emergency issues when LNAPL in the ground Vapor accumulation in confined spaces causing explosive conditions Not shown - Direct LNAPL migration to surface water Not shown - Direct LNAPL migration to underground spaces 1 2 3a 2 3b LNAPL considerations when LNAPL in the ground 2 Groundwater (dissolved phase) LNAPL to vapor Groundwater to vapor Not shown - Direct contact/ingestion after Garg and ITRC 2009 Additional LNAPL considerations when LNAPL in wells LNAPL potential mobility (offsite migration, eg to surface water, under houses) LNAPL in well (aesthetic, reputation, regulatory, recoverable) LNAPL Migration LNAPL Saturation LNAPL Composition 35

36 New Site: Initial Investigation Old Site: Review No Further Action 2 Remedy/Control Selection Initial CSM/LCSM Remedy/Control LCSM Design & Performance LCSM LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Design Remedy/Control; Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Alternative Evaluation Yes Yes Yes No CSM/LCSM Sufficient to Determine Concerns? Yes Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? LCSM Sufficient to Design Remedy/Control & Select Objective(s) & Metric(s)? Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 36

37 Link Concern to LNAPL Management Approach C sat Residual LNAPL present, but cannot flow into wells LNAPL Concern (Risk) Mobile LNAPL can flow into wells LNAPL is Source of Dissolved and Vapor Plumes Migrating Recoverable (MEP) Remedial Technology Groups Mass Control Mass Recovery Phase Change Respond to Actual LNAPL Risk 37

38 Remedy LCSM Questions What Concern Drives The Objective For Most LNAPL Depletion? How Is The LNAPL Distributed Above And Below The Water Table? How Permeable Is The Soil? How Heterogeneous and/or Layered Is The Permeability? How Volatile ls The LNAPL? What Fraction Is Volatile? Can Biodegradation Be Enhanced? 38

39 LNAPL Remedial Technologies Mass Control Physical containment In-situ soil mixing Mass Recovery LNAPL skimming Bioslurping/EFR Dual pump liquid extraction Multi-phase extraction Excavation Water/hot water flooding Cosolvent flushing Surfactant-enhanced subsurface remediation Phase Change Natural source zone depletion (NSZD) Air sparging/soil vapor extraction (AS/SVE) In situ chemical oxidation Heating Steam injection Electrical Resistance Conduction Dewatering & SVE (DPE) Biovent/Biosparge Anaerobic Bio-Oxidation 39

40 LNAPL Remedial Technologies Mass Control Physical containment In-situ soil mixing Mass Recovery LNAPL skimming Bioslurping/EFR Dual pump liquid extraction Multi-phase extraction, dual pump Excavation Water/hot water flooding Cosolvent flushing Surfactant-enhanced subsurface remediation Phase Change Natural source zone depletion (NSZD) Air sparging/soil vapor extraction (AS/SVE) In situ chemical oxidation Heating Steam injection Electrical Resistance Conduction Dewatering & SVE (DPE) Biovent/Biosparge Anaerobic Bio-Oxidation 40

41 New Site: Initial Investigation Old Site: Review No Further Action 3 Remediation/Control & Closure Initial CSM/LCSM Remedy/Control LCSM Design & Performance LCSM LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Design Remedy/Control; Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Alternative Evaluation Yes Yes Yes No CSM/LCSM Sufficient to Determine Concerns? Yes Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? LCSM Sufficient to Design Remedy/Control & Select Objective(s) & Metric(s)? Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 41

42 Design & Performance LCSM Questions What Conditions Should A Technology Change? What Conditions Will Demonstrate Desired LNAPL Changes? What Post-Remedial Conditions Will Demonstrate Success? When, For The Technology Selected, Will The Cost Of Incremental Change Become Too High? What Are The Lifecycle Costs Of Subsequent Technologies? 42

43 Specific Measurable Attainable Relevant Timely SMART Remedial Objectives & Metrics S M A R T 43

44 If LNAPL Recovery isn t Effective, Then What?

45 LNAPL Composition Risk Unstable LNAPL Stable LNAPL Residual LNAPL LNAPL Migration & Composition Risk LNAPL Composition Risk Only Risk = LNAPL Instability + LNAPL Composition 45

46 Mass Reduction & Composition Change

47 Mass Reduction vs Composition Change 47

48 Phase Change Technologies for All LNAPL C sat Residual LNAPL present, but cannot flow into wells LNAPL Concern (Risk) Mobile LNAPL can flow into wells LNAPL is Source of Dissolved and Vapor Plumes Migrating Recoverable (MEP) Remedial Technology Groups Mass Control Mass Recovery Phase Change Active Phase Change Depletes Mass Just Like NSZD 48

49 LNAPL Phase Change Technologies Mass Control Physical containment In-situ soil mixing Mass Recovery LNAPL skimming Bioslurping/EFR Dual pump liquid extraction Multi-phase extraction Excavation Water/hot water flooding Cosolvent flushing Surfactant-enhanced subsurface remediation Phase Change Natural source zone depletion (NSZD) Air sparging/soil vapor extraction (AS/SVE) In situ chemical oxidation Heating Steam injection Electrical Resistance Conduction Dewatering & SVE (DPE) Biovent/Biosparge Anaerobic Bio-Oxidation 49

50 LNAPL Phase Change Technologies Mass Control Physical containment In-situ soil mixing Mass Recovery LNAPL skimming Bioslurping/EFR Dual pump liquid extraction Multi-phase extraction Excavation Water/hot water flooding Cosolvent flushing Surfactant-enhanced subsurface remediation Phase Change Natural source zone depletion (NSZD) Air sparging/soil vapor extraction (AS/SVE) In situ chemical oxidation Heating Steam injection Electrical Resistance Conduction Dewatering & SVE (DPE) Biovent/Biosparge Anaerobic Bio-Oxidation How about ISCO? Pros: Inject in existing wells Short duration no ongoing O&M Cons: Let s examine 50

51

52 Objectives Define site characteristics that present challenges to in situ chemical treatment Discuss design considerations for in situ chemical treatment focused on management of contaminant rebound 52

53 Agenda What is in situ chemical treatment? The cause of the bounce Defining the in situ chemical treatment sweet spot Chemical treatment design considerations Summary 53

54 Reduction Reactions Defining In Situ Chemical Treatment Manipulating oxidation-reduction potential of constituents of concern (COC) to reduce mobility/toxicity O 2 NO 3 - H 2 O N 2 Conventional oxidation and reduction reactions applied to soil and groundwater Complicated by site-specific hydrogeology, geochemistry, and nature and extent of COCs Success predicated on achieving meaningful contact times between reagents and COCs MnO 2 Fe(OH) 3 Mn 2+ Fe 2+ Oxidation Reactions Fast kinetics, short residence times SO 4 2- HCO 3 - H 2 S CH 4 54

55 Available Treatment Chemistries Chemical Reduction Chemical Oxidation Stoichiometric Advanced Oxidation Process: Radicals 55

56 Oxidant Persistence Comparison Assumes constant groundwater velocity of 03 m/d Pseudo-first order kinetics NaP Therm NaP Alk 1 NaP Ambient Permanganate CHP NaP Acid NaP Alk 2 Ozone Applicable oxidants for petroleum hydrocarbons are CHP, ozone, and persulfate Distance in Meters from Injection Point Where Oxidant Concentration = 10% of the Injected Concentration ISCO for petroleum hydrocarbons is challenging, but persulfate can provide a longer in situ residence time than CHP and ozone 56

57 Oxidant Persistence Comparison (Arcadis, 2013) (Arcadis, 2014) (Arcadis, 2009) (Arcadis, 2015) (Ahmad et al, 2010) (Ahmad et al, 2010) (Liang et al, 2003) (Siegrist et al, 2011) 308 m 6780 m 7631 m 3265 m 270 m 3510 m 026 m 017 m Assumes constant groundwater velocity of 03 m/d Pseudo-first order kinetics NaP Therm NaP Alk 1 NaP Ambient Permanganate CHP NaP Acid NaP Alk 2 Ozone Applicable oxidants for petroleum hydrocarbons are CHP, ozone, and persulfate Distance in Meters from Injection Point Where Oxidant Concentration = 10% of the Injected Concentration ISCO for petroleum hydrocarbons is challenging, but persulfate can provide a longer in situ residence time than CHP and ozone 57

58 All hydrogeological systems are heterogeneous and anisotropic 58

59 10-2 cm/sec (Clean Sand) 10-6 cm/sec (Clay) 10-4 cm/sec (Silty Sand) 59 59

60 10-2 cm/sec (Clean Sand) 10-6 cm/sec (Clay) 10-4 cm/sec (Silty Sand) Flow (> 90%) Flow (~01%) 60 Flow (< 10%) 60

61 Three Compartment Model New Standard of Practice Flow 90% Fast GW 9% Slow GW 1% Static GW Mobile Fraction m Mass Transfer Immobile Fraction i Diffusion Storage Fraction s Advective Zones Pure Advection (Mobile Fraction) Sand & Gravel Hydraulic Conductivity > 10-2 cm/sec Advective & Storage Zones Slow Advection (Immobile Fraction) Silty and Clayey Sand 10-4 < Hydraulic Conductivity < 10-2 cm/sec Storage Zones Static Water (Storage Fraction) Sandy Silt, Silt, and Clay Hydraulic Conductivity < 10-4 cm/sec Advection / Advection & Diffusion / Diffusion 61

62 Plume Development Washout profile during aquifer flushing A B C D 62

63 Conceptual Site Model (CSM) Reference CSM Mass Flux Mobile Fraction m Readily addressed by In Situ Treatment Mass Transfer Immobile Fraction i Potentially addressed by In Situ Treatment Diffusion Stationary Fraction s Difficult to address with In Situ Treatment Discusses where COCs are; equally important is how much remains 63

64 Chemical Treatment Sweet Spot Delivery Delivery means reagent distribution at a working strength 64

65 Chemical Treatment Sweet Spot Delivery Contact Delivery means reagent distribution at a working strength Contact time of reagent and contaminant is critical 65

66 Chemical Treatment Sweet Spot Delivery Contact Access Delivery means reagent distribution at a working strength Contact time of reagent and contaminant is critical Access to source mass refers to where its located and how much remains 66

67 Chemical Treatment Sweet Spot Delivery Contact Access Regulatory Delivery means reagent distribution at a working strength Contact time of reagent and contaminant is critical Access to source mass refers to where its located and how much remains Flexible regulatory framework 67

68 Designing Chemical Treatment Optimizing of Reagent Distribution Sufficient permeability to support injections Volume to distribution relationship Reagent residence time (ie, washout versus consumption) Continuous down-hole specific conductivity measurements 68

69 Designing Chemical Treatment Optimizing of Reagent Distribution Sufficient permeability to support injections Volume to distribution relationship Reagent residence time (ie, washout versus consumption) Role of Treatability Testing Oxidant/reductant demand? Buffering capacity? Leverage experience to reduce cost Continuous down-hole specific conductivity measurements ISCO treatability testing 69

70 Designing Chemical Treatment Optimizing of Reagent Distribution Sufficient permeability to support injections Volume to distribution relationship Reagent residence time (ie, washout versus consumption) Role of Treatability Testing Oxidant/reductant demand? Buffering capacity? Leverage experience to reduce cost Nature and Extent of Contamination NAPL? Adsorbed mass (soil concentrations)? Historical contaminant concentrations and groundwater elevations ( smear zone )? Continuous down-hole specific conductivity measurements ISCO treatability testing 70

71 Groundwater Flow Dispersion and Remediation Small volume, large spread the lampshade Injected volume radius influenced relationship; near zero transverse dispersivity Sufficient overlap to ensure radial treatment 71

72 Vinj/3 m (L) Optimizing Reagent Distribution 10,000 Vol inj = π ROI 2 h screen θ m Mobile Fraction 030 8, ,000 4,000 2, Radial Distance (m)

73 Vinj/3 m (L) Optimizing Reagent Distribution 10,000 8,000 6,000 4,000 2,000 0 Vol inj = π ROI 2 h screen θ m Appropriate injection volumes are typically 1/3 of the total pore volume of the targeted treatment area Supported by tracer testing and dose response monitoring Radial Distance (m) Mobile Fraction Permeability 73

74 Injection Rate, gpm Response DTW, ft Reagent Distribution Example Sp Cond S 2 O 8 2- ph DTW ,000 10,000 15,000 20,000 Cumulative Injected Volume (gal) ,000 10,000 15,000 20,000 Cumulative Injected Volume (gal) 74

75 Injection Rate, gpm Response DTW, ft Reagent Distribution Example Sp Cond S 2 O 8 2- ph DTW Dose response data within the planned ROI remained uninfluenced; inefficient volume to distribution relationship ,000 10,000 15,000 20,000 Cumulative Injected Volume (gal) ,000 10,000 15,000 20,000 Cumulative Injected Volume (gal) 75

76 Role of Treatability Testing Laboratory Treatability Test Verify chemistry if novel contaminant or questionable site geochemistry Proof of concept Establish oxidant and activator dosing Focus on required reagent, not the natural oxidant demand (NOD) or total oxidant demand (TOD) Screen secondary effects VOCs and metals 76

77 Oxidant Reagent Chemistry Secondary effect example Chlorinated ethanes formed from chloromethanes 77

78 Oxidant Reagent Chemistry Chlorinated ethanes formed from chloromethanes Secondary effect example X = H or Cl X X X X Chloroethenes, hydrocarbons, DOC, or NOD react with radical chlorine 78

79 Oxidant Reagent Chemistry Chlorinated ethanes formed from chloromethanes Secondary effect example X = H or Cl X X X X Chloroethenes, hydrocarbons, DOC, or NOD react with radical chlorine Cl Cl Cl Cl 1,2-DCA Resultant carbon-based radical precusor may form chloroethanes Cl Cl Cl Cl Cl Cl 1,1,2-TCA Organic molecules enhance this process 79

80 Normalized Benzene (Logarithmic Scale) Normalized Persulfate Lab-Scale to Field-Scale 10 Lab treatability study supports activated persulfate for risk-based objectives CSM shows differing permeability (low permeability in a unit, high permeability in b unit) 10% 8% 1 6% 4% 2% 01 0% Elapsed Time Since Injection (d) MW-6a Benzene MW-6b Benzene MW-6a Persulfate MW-6b Persulfate Injection Event 80

81 Normalized Benzene (Logarithmic Scale) Normalized Persulfate Lab-Scale to Field-Scale 10 ISCO disqualified as a cost-effective treatment based on residual source mass and challenging distribution in a unit 10% Increased normalized benzene above 1 indicates dissolution of source mass 8% 1 6% 4% 2% 01 0% Elapsed Time Since Injection (d) MW-6a Benzene MW-6b Benzene MW-6a Persulfate MW-6b Persulfate Injection Event 81

82 [BTEX]tot (ug/l) GW Elev (ft amsl) ISCO and the Smear Zone Tot BTEX GW Elevation Injection Events Similar observation after subsequent injections No more injections, what caused the greatest rebound? Initial increase, decline postinjection Jul-12 Mar-13 Nov-13 Jul-14 Apr-15 Dec

83 [BTEX]tot (ug/l) GW Elev (ft amsl) ISCO and the Smear Zone Tot BTEX Injection Events GW Elevation GW elevation data reveals the potential for a submerged source 01 Jul-12 Mar-13 Nov-13 Jul-14 Apr-15 Dec

84 [BTEX]tot (ug/l) GW Elev (ft amsl) ISCO and the Smear Zone (cont) Tot BTEX Injection Events GW Elevation A historical review strongly suggests smear zone impacts and submerged source mass 01 May-03 May-05 Jun-07 Jul-09 Jul-11 Aug-13 Sep Smear zones can control rebound post ISCO 84

85 85 [BTEX] (μg/l) Groundwater Elevation (ft) Evidence of Improvement via ISCO 100,000 BTEX Injection Event GWE 89 10,000 1, Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 85

86 86 [BTEX] (μg/l) (B + T) / (E + X) Groundwater Elevation (ft) Evidence of Improvement via ISCO 100,000 BTEX Injection Event GWE 89 10,000 1, Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 5 B + T 4 E + X = Benzene + Toluene Ethylbenzene + Xylenes Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 86

87 87 [BTEX] (μg/l) (B + T) / (E + X) Groundwater Elevation (ft) Evidence of Improvement via ISCO 100,000 BTEX Injection Event GWE 89 10,000 1, Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 5 B + T 4 E + X = Benzene + Toluene Decrease in ratio Ethylbenzene + Xylenes implies advanced 3 weathering reduced toxicity profile Oct-06 Jul-09 Apr-12 Dec-14 Sep-17 87

88 Sweet Spot ISCO Pilot area ISCO as a polishing technology following a large source removal TCE in groundwater (<50 μg/l) above NYSDEC goal (5 μg/l) GW ISCO design supported with laboratory treatability testing and field-scale pilot testing Rely on advective transport for distribution of oxidant (30 day oxidant persistence as confirmed during pilot testing) Two years post treatment: two locations 5 to 10 μg/l TCE Treatment Area Source Removal 88

89 Chemical Treatment Applicability Summary Safe and complete execution: achieving dose response, responding to data, reagent residence time, secondary effects Robust design: adequate injection volumes, reagent-contaminant contact, reagent chemistries, geochemical considerations, proof of concept Site characterization: nature and extent of contamination can preclude chemical treatment as an option or dictate its implementation 89

90 If ISCO Isn t Effective, Then What?

91 Natural Source Zone Depletion 100s to 1,000s of gallons/(acre year) Acts on entire LNAPL body Effective for all LNAPLs Depletes soluble and volatile fractions first, ie, weathering 91

92 Enhance NSZD Surface Application ABOx Inject into saturated zone air/oxygen (biosparge) Inject soluble electron acceptor (ABOx) nitrate sufate Inject into vadose zone air/oxygen (biovent) Aerobic processes demonstrated faster than NSZD CAUTION! Some ABOx challenges similar to those of ISCO stoichiometry delivery 92

93 Volatilize LNAPL & Enhance Aerobic Degradation 93 Unsaturated Zone Capillary Zone LNAPL Soil Vapor Groundwater Extraction Pump Soil Vapor Discharge Groundwater Discharge Air Sparging / Soil Vapor Extraction Dewater Dual-Phase Extraction aka, Dewatering & SVE Effective for volatile LNAPL High initial mass reduction

94 Elev (m) Heating Technologies A B B Section A-A A Vapor line Electrode y-distance (m) o C ITRC 2010; I Hers, Golder Effective for low volatility LNAPLs Fast depletion of high volatility LNAPL constituents High mass reduction 94

95 Summary

96 Risk-Based LNAPL Management Approach Unstable LNAPL Stable LNAPL Residual LNAPL LNAPL Migration & Composition Risk LNAPL Composition Risk Only Risk = LNAPL Instability + LNAPL Composition 96

97 New Site: Initial Investigation Old Site: Review No Further Action LCSM Supports Alternative Evaluation Initial CSM/LCSM Remedy/Control LCSM Design & Performance LCSM LCSM Establish LNAPL Concerns Establish LNAPL Remedial/Control Goal(s) Select LNAPL Remedy(ies)/Control(s) Design Remedy/Control; Establish Objectives(s) & Metric(s) Operate Remedy(ies)/Control(s) Alternative Evaluation Yes Yes Yes No CSM/LCSM Sufficient to Determine Concerns? Yes Remedy/Control Required? LCSM Sufficient to Select Remedy(ies)/Control(s)? LCSM Sufficient to Design Remedy/Control & Select Objective(s) & Metric(s)? Do Metrics Demonstrate Objective(s) and Goal(s) Are Met? No No No No Yes 97

98 Phase Change Technologies for All LNAPL C sat Residual LNAPL present, but cannot flow into wells LNAPL Concern (Risk) Mobile LNAPL can flow into wells LNAPL is Source of Dissolved and Vapor Plumes Migrating Recoverable (MEP) Remedial Technology Groups Mass Control Mass Recovery Phase Change Active Phase Change Depletes Migrating, Mobile & Residual LNAPL 98

99 Ole Reliable Phase Change Technologies Mass Control Physical containment In-situ soil mixing Mass Recovery LNAPL skimming Bioslurping/EFR Dual pump liquid extraction Multi-phase extraction Excavation Water/hot water flooding Cosolvent flushing Surfactant-enhanced subsurface remediation Phase Change Natural source zone depletion (NSZD) Air sparging/soil vapor extraction (AS/SVE) In situ chemical oxidation Heating Steam injection Electrical Resistance Conduction Dewatering & SVE (DPE) Biovent/Biosparge Anaerobic Bio-Oxidation 99

100 ITRC LNAPLs guidance used or referenced in the development of current or draft state guidance ITRC LNAPL document used or planned use at sites (reports by all environmental sectors) Link to State Guidance that References ITRC LNAPL Documents at wwwitrcweborg/lnapls under Resources & Links 100

101 Thank you! RICK AHLERS, PE Technical Expert, Engineer LNAPL Management Global CoP Lead o c e rickahlers@arcadiscom JEFF MCDONOUGH, PE Principal Environmental Engineer North American PFAS co-lead o c e jeffreymcdonough@arcadiscom 101