Integrated DNAPL Site Strategy (IDSS)

Transcription

1 Integrated DNAPL Site Strategy (IDSS) Sydney, Australia September 2014 Melbourne, Australia October 2014 Naji Akladiss, P.E., Maine DEP Charles (Chuck) Newell, Ph.D., P.E., GSI Environmental Inc. Tamzen Macbeth, Ph.D., P.E., CDM Smith Heather Rectanus, Ph.D., P.E., Battelle

2 2 The Problem Are you tired of throwing money and time at your chlorinated solvent sites with little improvement in return?

3 3 The Solution is an Integrated DNAPL Site Strategy (IDSS) u Comprehensive site management u When can you develop an IDSS? Anytime! u Who should use this IDSS? Experienced practitioners and regulators ITRC Technical and Regulatory Guidance Document: Integrated DNAPL Site Strategy (IDSS-1, 2011)

4 4 An Integrated DNAPL Site Strategy u Conceptual site model Chapter 2 u Remedial objectives Chapter 3 u Remedial approach Chapter 4 u Monitoring approach Chapter 5 u Evaluating your remedy Chapter 6 ITRC IDSS-1, Figure 1-2

5 5 An IDSS Considers: u Better ways to conceptualize the problem: Improved understanding of plume architecture and evolution flux-based decision making u Making objectives SMART: Specific, Measureable, Attainable, Relevant, and Time-bound u Linking source-plume remedies; when to change u Appropriate monitoring strategies u Re-evaluating and optimizing

6 6 Chapter 2: Conceptual Site Model (CSM)

7 7 Technical Concepts We Will Cover Related to CSM Five topics in compartment model slides

8 8 Chlorinated Solvent Releases Chemical Phases and Transport u DNAPL movement and capillary forces u Chemical phase distribution u Interphase chemical mass transfer u Dissolved plume formation & transport u Vapor migration Generalize DNAPL Release and Transport vapor Dissolved Plume Degradation Reactions Sorption, etc. (Modified from Parker et al., 2002) DNAPL Pore-Scale Distribution Sand Grains Water DNAPL Interphase Chemical Mass Transfer DNAPL Vapor Aqueous Sorbed ITRC IDSS-1, Figures 2-1, 2-3

9 9 Importance of Geologic Heterogeneity u Tools and concepts commonly applied often underrepresent the actual complexity of DNAPL sites Simplified Geologic Concepts Reality is Complex! Intermediate Complexity Models ITRC IDSS-1, Figure 2-4

10 10 Geologic X-Section: Setting the Stage for a DNAPL Release Key Point: Groundwater flux is dominant in high-permeability zones Groundwater velocity in high-permeability zones >>> average value Water Table Groundwater Flow Low Permeability Zones Medium Permeability High Permeability Zone Highly simplified illustration of heterogeneous geology

11 11 Source-Plume Evolution: Early Stage Dominant Early Stage Process: Diffusion from high to low concentration Out of high permeability zone Source Area Plume Area Groundwater Flow Green = Lower Concentration Highly simplified illustration of heterogeneous geology

12 12 Source-Plume Evolution: Middle Stage Dominant Middle Stage Process: Relatively uniform contaminant distribution Diffusion at a minimum Source Area Plume Area Groundwater Flow Yellow = Moderate Concentration Low Permeability Zones Highly simplified illustration of heterogeneous geology

13 13 Source-Plume Evolution: Late Stage Dominant Late Stage Process: Diffusion out of low permeability zones Mass tied up in low permeability zones Source Area Plume Area Groundwater Flow Low Permeability Zones Green = Lower Concentration Highly simplified illustration of heterogeneous geology

14 14 14-Compartment Model u u Compartment consists of chemical phase within either the source zone or plume and in either transmissive or low permeability zone Highly conceptualized depiction of potential for contaminant mass flux between compartments Source Zone Plume Phase/Zone Low Perm. Transmissive Transmissive Low Perm. Vapor DNAPL NA NA Aqueous Sorbed ITRC IDSS-1, Table 2-2 from Sale and Newell, 2011

15 15 Chapter 3: Remedial Objectives Chapter 3 Remedial objectives Set/revisit Functional Objectives u How do you define objectives in a clear and concise manner? u What is the process to make your objectives specific, measureable, attainable, relevant, and time bound? (Doran 2008) u Simple Example

16 16 Types of Objectives u Absolute objectives Based on broad social values Example: protection of public health and the environment u Functional objectives Steps taken to achieve absolute objectives Example: reduce loading to the aquifer by treating, containing, or reducing source

17 17 Functional Objectives Should be SMART SMART means: u Specific Objectives should be detailed and well defined u Measureable Parameters should be specified and quantifiable u Attainable Realistic within the proposed timeframe and availability of resources u Relevant Has value and represents realistic expectations u Time-bound Clearly defined and short enough to ensure accountability

18 18 Functional Objectives Time Frame u Time frame should accommodate Accountability Natural variation of contaminant concentration and aquifer conditions Reliable predictions Scientific understanding and technical ability u Team suggests 20 years or less for Functional Objectives Site management and active remediation timeframe may continue for much longer

19 19 Example Site u u u Potential future indoor air vapor risk PCE in vadose zone and groundwater PCE in groundwater is a potential drinking water risk PCE in soils is a contact and ambient air risk 1,800 ug/l 4,000 ug/kg u u PROPOSAL Redevelop the property with no environmental restrictions CLEANUP 40 µg/kg PCE in soil, 8 µg/l and 5 µg/l PCE in groundwater ITRC IDSS-1, Figure 2-12

20 20 Developing a Functional Objective for the Example Site u Absolute Objectives: Protection of human health and the environment Redevelop the Mall Area u Generic Functional Objective - Not SMART Vapor Intrusion Indoor Air Objective Soils Pathway Reduce concentrations of volatile organics in the vadose zone that will allow a No Further Action for unrestricted use, with no engineering or administrative controls required

21 21 SMARTify the Functional Objective u SMART Functional Objective Reduce concentrations of volatile organics in the vadose zone to less than 40 µg/kg within 6 months that will allow a No Further Action for unrestricted use, with no engineering or administrative controls required u Meets SMART Criteria Specific Yes, 40 µg/kg Measureable Yes, confirmation samples Achievable Yes, excavation or SVE or ISCO Relevant Yes, intended use of property Time-bound Yes, 6 months

22 22 ASK THE CLASS u Give an example of a smart objective that could be applied to one of your sites.

23 23 Chapter 4: Treatment Technologies Chapter 4 Treatment Technologies Evaluate/re- evaluate and select technologies Yes Implement the technology(ies) u How do you to avoid the trap of relying on a single remedial technology that won t do the job? u How do you consider site characteristics and site goals when deciding on technologies? u How could multiple technology selection and integration help you reach your functional objectives?

24 24 Four Parts to Section 4 u Remediation technologies and assessing performance (Section 4.1) u Coupling technologies (Section 4.2) u Transitioning to other technologies (Section 4.3) u Example (Section 4.4)

25 25 But in 2011: daunting environmental challenge Restoring sites has been exceptionally difficult Google ITRC IDSS

26 26 Order of Magnitude are Powers of 10 Why Use OoMs for Remediation? u Hydraulic conductivity is based on OoMs u VOC concentration is based on OoMs u Remediation performance (concentration, mass, Md) can be also evaluated using OoMs. 90% reduction: 1 OoM reduction 99.9% reduction: 3 OoM reduction 70% reduction: 0.5 OoM reduction (use equation 4.1.1) u Example: Before concentration 50,000 ug/l After concentration 5 ug/l Need 4 OoMs (99.99% reduction)

27 27 Remediation Performance: Parent CVOC 1000 SOURCE REMEDIATION PERFORMANCE What Happened At 216 Sites Source: McGuire et al., 2014 ESTCP Project Development of an Expanded, High-Reliability Cost and Performance Database for In-Situ Remediation Technologies Site Concentration After Treatment (mg/l) Bioremediation (n=108) Chemical Oxidation (n=58) Thermal Treatment (n=24) Zero Valent Iron (n=22) Surfactant/Cosolvent (n=4) MCL Site Concentration Before Treatment (mg/l) 27

28 28 Technology Compatibility Matrix u Compatibility matrix of 9 technologies u Examples: Generally Compatible Thermal followed by In Situ Bio: Potentially synergistic Microbes population may be reduced But then rapid recovery Likely Incompatible In Situ Reduction followed by In-Situ Oxidation Destruction of both reagents Potentially Compatible but Not An Anticipated Couple ITRC IDSS-1, Table 4-2 Bio followed by Surfactant Flushing Would probably work, but unlikely to be coupled

29 29

30 30 Transitioning Between Technologies (Section 4.3) Potential Transition Triggers: u Contaminants concentrations Most likely to be contacted by the public or environment Concentrations in a single key phase u Contaminant phase (particularly free phase) u Contaminant lineage, parent vs. daughters u Site conditions created during method execution u Cost per unit of contaminant destroyed

31 31 Chapter 5: Monitoring Chapter 5 Has a more efficient alternative become available? Monitoring No Monitor performance For each treatment area u How do you design a monitoring program that assesses your progress towards reaching your functional objectives? u What data should you collect to evaluate remedy performance?

32 32 Type of Monitoring u Performance Monitoring At end of the day, did it work? Compare to SMART functional objectives u Process Monitoring We turned it on is it working correctly? Data used to optimize system u Compliance Monitoring How are we compared to regulatory limits? Is everyone safe? Point of Compliance Well

33 33 Metrics u Concentration u Mass of contaminants: u Mass Flux Mass Discharge mg/l, mg/kg, ppmv Kilograms Grams per m 2 per day Grams per day

34 34 Data Evaluation u Key concept: Maintaining and Improving the Conceptual Site Model Visualization tools can help Stats help you understand trends City Supply Well Source Area Plume

35 35 Optimizing Monitoring u Monitoring network Any redundant wells or data gap area? u Frequency and duration Do I need to sample quarterly? Lots of research. u Contaminant and constituent Can 1 or 2 compounds explain the big picture? u Key tools: MAROS and GTS

36 36 Chapter 6: Remedy Evaluation u How do you create a plan to evaluate, optimize, and revise your remedial strategy? Chapter 6 Re- evaluate the basis of your original decisions beginning with the CSM Yes Is progress toward the Functional Objectives acceptable? No Remedy evaluation No Evaluate progress Are Functional Objectives met? Yes Closure Strategy ITRC IDSS-1, Figure 1-2 excerpt

37 37 Key Questions to Consider u Are Functional Objectives being met is progress acceptable? u Can you be more efficient? u How do you troubleshoot if you are not? ITRC IDSS-1, Figure 1-2 excerpt

38 38 Troubleshooting: Revisit CSM u Common inaccuracies 3D delineation Boundary conditions Surface features Multiple / alternate source Age and nature of release Heterogeneity Diffusion Seasonal changes Preferential pathways Vapor phase transport Groundwater Flow Source Area Plume Area Source treatment Low Permeability Zones Green = Lower Concentration

39 39 Troubleshooting: Revisit Objectives ITRC IDSS-1, Figure 1-2 excerpt Reasons objectives dont work: u Metrics not aligned with objectives u Unrealistic expectations of technology performance u Data does not support objectives u Regulatory goals not achievable in predicted time u Lack of interim objectives u NEED TO BE SMART

40 40 Troubleshooting: Technology ITRC IDSS-1, Figure 1-2 excerpt u Technology performance evaluation Expected versus actual performance u Technology performance expectations Appropriate technologies based on the revised site understanding and the actual performance of technologies already employed u Technology cessation/ addition/transition Re-evaluate the technology(ies) in use to other applicable technologies

41 41 Course Summary u Maintain and improve conceptual site model u SMART functional objectives u Multiple technologies u Iterative performance evaluation u Reevaluate your strategy u Regulatory issues An IDSS creates an accurate, comprehensive management model for sites where chlorinated solvent occurs in multiple phases and is remediated using several methods over an extended period of time and under conditions of uncertainty and change

42 42 Mini Example: 14-Compartment Model Relative aqueous phase equivalent concentrations not mass based Early Stage ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor LOW MODERATE LOW LOW DNAPL LOW HIGH Aqueous LOW MODERATE MODERATE LOW Sorbed LOW MODERATE LOW LOW ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor DNAPL Aqueous Sorbed ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor DNAPL Aqueous Sorbed Middle Stage Late Stage

43 43 Mini Example: 14-Compartment Model ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor LOW MODERATE LOW LOW DNAPL LOW HIGH Aqueous LOW MODERATE MODERATE LOW Sorbed LOW MODERATE LOW LOW ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor MODERATE MODERATE MODERATE MODERATE DNAPL MODERATE MODERATE Aqueous MODERATE MODERATE MODERATE MODERATE Sorbed MODERATE MODERATE MODERATE MODERATE ZONE SOURCE PLUME Lower-K Transmissive Transmissive Lower-K Vapor LOW LOW LOW LOW DNAPL LOW LOW Aqueous MODERATE LOW LOW MODERATE Sorbed MODERATE LOW LOW MODERATE Early Stage Middle Stage Late Stage