1 / 57

Welcome to ITRC’s Internet Training

Welcome to ITRC’s Internet Training. Historical Case Analysis of Chlorinated Volatile Organic Compound Plumes March 1999. Sponsored by the ITRC, EPA-TIO & Lawrence Livermore National Laboratory. Today’s Presenters. Greg Bartow, R.G., CH.g. California RWQCB gwb@rb2.swrcb.ca.gov

javan
Télécharger la présentation

Welcome to ITRC’s Internet Training

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Welcome to ITRC’s Internet Training Historical Case Analysis of Chlorinated Volatile Organic Compound Plumes March 1999 Sponsored by the ITRC, EPA-TIO & Lawrence Livermore National Laboratory

  2. Today’s Presenters • Greg Bartow, R.G., CH.g. • California RWQCB • gwb@rb2.swrcb.ca.gov • Walt McNab • Environmental Protection Department, Lawrence Livermore National Lab • mcnab1@llnl.gov • David Rice • Environmental Protection Department, Lawrence Livermore National Lab • rice4@llnl.gov

  3. Presentation Overview • About the ITRC • Description of the methodology and results of a statistical evaluation of hydrologic and contaminant data from chlorinated compound contaminated plumes • Questions and Answers • Wrap-up and Links to additional • information and resources

  4. Who’s Involved? STATE-LED INITIATIVE WITH: • 38 States (and growing) • Sponsoring State Organizations Environmental Western Southern States Council of Governors’ Energy Board the States Association • Public/Tribal Stakeholders • Industry Representatives • DOEUS EPADOD

  5. Creating Tools and Strategies to Reduce Technical and Regulatory Barriers to the Deployment of Innovative Environmental Technologies Active ITRC States • In Situ Bioremediation • DNAPLs/In Situ Chemical Oxidation • Permeable Reactive Walls • Radionuclides • Unexploded Ordnance • In Situ Biodenitrification • Phytoremediation • Verification • Diffusion Sampler

  6. Purpose of this Training • Understand the factors affecting behavior of the CVOC plumes in ground water from a broad, statistically oriented perspective • Enhance your understanding of plume behavior through examination of data from many sites • Allow you to focus on the major factors influencing plume behavior increase the efficiency of planning site investigations and cleanup

  7. CVOC Historical Case Analysis — Goals • Gather case information from over 200 VOC plumes • Nation-wide “plumathon” • DOE, DOD, Industry, ITRC States, EPA • Perform analysis that is defensible and peer reviewed • Expert Working Task Force • Expert Peer Review Panel • Findings and Conclusions based on case analysis • Working Task Force prepares • Peer Review Panel reviews • Recommendations for Policy Change • Interstate Technology and Regulatory Cooperation Task Force (ITRC) prepares • Peer Review Panel reviews

  8. Working Task Force • Greg Bartow—California RWQCB • Jacob Bear—Technion Institute of Technology • Mike Brown/Paul Zielinski—DOE • Patrick Haas—DOD/USAF • Herb Levine—EPA • Curt Oldenburg/Tom McKone—LBL • Mike Kavanaugh—Industry • Bill Mason/Paul Hadley—ITRC • Doug Mackay/Christina Hubbard—University of Waterloo • Mohammad Kolhadooz—Industry • Mike Pound—DOD/USN • Dave Rice (Initiative Coordinator)—LLNL • Heidi Temko—California SWRCB • Cary Tuckfield—Savannah River Technology Center • Walt McNab (Data Analysis Team Leader)—LLNL • Richard Ragaini (Data Collection Team Leader)—LLNL

  9. Peer Review Panel • David Ellis–Dupont • Lorne Everett–UC Santa Barbara/Geraghty & Miller • Marty Faile–USAFCEE • William Kastenberg–University of California, Berkeley • Perry McCarty–Stanford University • Hanadi Rifai–Rice University • Lenny Siegel—Pacific Studies Center • Todd Wiedemeier–Parson’s Engineering • John Wilson–U.S. EPA, ORD

  10. CVOC Historical Case Analysis — Potential Benefits to Nation • What are the advantages to looking at CVOC plumes nationwide? • Similar sites can share common lessons learned • High or Low risk VOC release scenarios can be identified • Help understand where natural attenuation may be applicable • Reduced Cleanup Costs • Focus characterization costs on those factors that most influence plume behavior • Technology Market Identified • Analysis of large number of cases identifies technology needs • Defines technology functional requirements

  11. VOC Historical Case Analysis — Hypothesis & Questions • Hypothesis: Chlorinated solvent cases have natural groupings • Hypothesis: These groupings can identify sites that have common predictable characteristics

  12. CVOC Historical Case Analysis —Specific Questions • How often is a dense non-aqueous phase liquid (DNAPL) inferred to be present. • Are Plumes with possible DNAPLS longer? • How often is there evidence of transformation processes • Are plumes with CVOC transformations shorter? • Do daughter product plumes behave differently compared to parent CVOC plumes?

  13. Historical Case Analysis: A New Data Model • Much of our knowledge of plume behavior comes from well-instrumented research sites. • Much of the CVOC groundwater data is collected at poorly-instrumented sites targeted for cleanup. • Historical case analyses offers a means for systematically analyzing these data.

  14. Project Scope Source term • Collect hydrogeologic and contaminant data from many sites reflecting diverse environmental and release settings. • Estimate representative values for key variables. • Employ statistical methods to assess relationships between dependent and independent variables. • Validate results with probabilistic modeling. Advection Transformation

  15. Rules, Definitions, and Assumptions • “Plume” defined per CVOC per site. • Minimum site characterization requirements. • Site exclusion criteria. • Daylighting plumes. • Plumes undergoing active pump-and-treat. • Plumes that were highly complex as a result of unusual conditions. MW-1 MW-3 MW-2 Plume length (10 ppb) MW-6 (100 ppb) MW-4 MW-5 MW-7 Length = Distance from location of max. historical concentration to distal 10-ppb contour.

  16. Definitions of Major Variables • Independent variables • Source strength • Mean groundwater velocity • Reductive dehalogenation category assignment • Dependent variables • Plume length • Change in plume length over time (growth rate)

  17. Project Data Set • 65 sites included in initial study; over 100 in current data set. • Data from a variety of release scenarios and sources: • D.o.D. and D.O.E. facilities • Dry cleaners • Commercial industrial sites • Landfills

  18. Plume Length Distributions

  19. Plume Length and Source Strength 100-ppb plumes R = 0.40, p = 2 x 10-6

  20. Groundwater Velocity 50th percentile ~ 0.2 ft/day • Mean groundwater velocity, v, estimated from Darcy’s law: • Geometric mean K estimated from site pumping tests and slug tests. • Mean hydraulic gradient from potentiometric surface maps. • Mean porosity assumed to be equal to 0.25. 10th percentile ~ 0.005 ft/day 90th percentile ~ 6 ft/day

  21. Plume Length and Groundwater Velocity 4 R = 0.46, p = 0.006 r = 0.46, p = 0.006 2 0 -2 -4 -6 -8 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 Log velocity (ft/day) Log plume length (ft)

  22. Reductive Dehalogenation No reductive dehalogenation group: 23 sites, no daughter products Strong reductive dehalogenation group: 20 sites, cis-1,2-DCE and vinyl chloride Weak reductive dehalogenation group: 18 sites, cis-12,-DCE but no vinyl chloride

  23. Example: Reductive Dehalogenation at Site 41350001 Coincident PCE and vinyl chloride plumes VC and benzene (ppb) Cl- (ppm) PCE conc. (ppb) GW flow direction

  24. Reductive Dehalogenation: Distributions of Plume Lengths No. of plumes CDF Plume length (ft) ANOVA: No significant differences between distributions Logarithm of plume length (ft)

  25. Where is the reductive dehalogenation effect? • Plume length reduction by reductive dehalogenation is subtle compared to groundwater velocity and source strength effects. • Biases in the data collection/analyses processes skew the results between groupings.

  26. Biases in the Data Set 100% 90% 80% 70% 60% Cumulative distribution 50% 40% Strong RD sites have significantly stronger source terms (p = 0.007). 30% 20% 10% 0% 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 Max. site concentration (ppb) No RD Strong RD • Site groundwater velocity contrasts: • For Strong-RD group, median groundwater velocity is 0.21 ft/day. • For No-RD group, 9 of 13 sites have mean velocities below the Strong-RD group median.

  27. Biases in Data Set (cont’d) No RD No RD Strong RD Strong RD No. No. Plume length Plume length • Site screening process may preferentially exclude certain types of sites: • Small source, low velocity, reductive dehalogenation  very small plumes not likely to be well-monitored (excluded). • Large source, high velocity, no transformation  very large plumes likely to be subject to early remediation (excluded).

  28. Biases in the Data Set: Source Strength and Groundwater Velocity p = 0.018

  29. Analysis of Covariance Sites with no evidence of reductive dehalogenation Sites with strong evidence of reductive dehalogenation Geometric means of raw plume lengths 876ft 872ft Adjusted geometric means (ANCOVA) 1047ft 510ft

  30. QUESTIONS AND ANSWERS C0 R,  v Plume length

  31. Probabilistic Modeling Groundwater velocity Sensitivity? Plume length Solute transport model Degradationrate

  32. Simulation: Overview C0 R,  v Plume length • Analytical solute transport solution used as model of “average” plume behavior. • Monte Carlo techniques used to generate a synthetic plume set. • Probability distributions of input variables developed from project database. • Two synthetic populations - one transforming and one stable - used to assess reductive dehalogenation effects. Monte Carlo analysis with Domenico (1987) model

  33. Plume Length as a Function of Source Strength: Simulation vs. Observation Observed Plume Set (10-ppb plumes) Simulated Plume Set R = 0.36 R = 0.20

  34. Plume Length as a Function of Ground Water Velocity: Simulation vs. Observation Observed Plume Set (10-ppb plumes) Simulated Plume Set 4 4 R = 0.64 R = 0.46 2 2 0 0 Log velocity (ft/day) Log velocity (ft/day) -2 -2 -4 -4 -6 -6 -8 -8 2.0 2.5 3.0 3.5 4.0 4.5 2.0 2.5 3.0 3.5 4.0 4.5 Log plume length (ft) Log plume length (ft)

  35. Contaminant Transformation and Plume Length: Simulation vs. Observation Observed Plume Lengths p = 0.91 Cumulative distribution Simulated Plume Lengths Plume length (ft) p = 0.51 Cumulative distribution Plume length (ft)

  36. Analysis of Covariance: Model Output Stable plumes Transforming plumes Geometric means of raw plume lengths 790 ft 884 ft Adjusted geometric means (ANCOVA) 991 ft 705 ft

  37. Temporal Analysis of CVOC Measurements in Wells TCE concentrations in 533 wells from 41 sites • Analyze temporal trends in data to discern natural attenuation effects • Methodology: • Rank-based linear regression with time • 5 or more distinct sampling events • R < -0.5  declining trend • R > 0.5  increasing trend

  38. Temporal Trends Compound No. of wells No. of sites Decline: increase Benzene 35 9 7.0 1,1,1-TCA 134 19 6.5 Toluene 21 8 4.5 TCE (+ vinyl chloride) 74 11 3.9 1,2-DCA 34 10 3.5 Chloroform 55 8 2.7 1,1-DCE 183 20 2.6 TCE 533 41 2.5 1,1-DCA 107 17 2.1 PCE 95 21 2.1 Cis-1,2-DCE 63 11 1.2 Vinyl chloride 125 12 0.9 Carbon tetrachloride 97 4 0.7

  39. Ratio Analysis: 1,1,1-TCA and 1,1-DCE Median ratio at source: 0.25 Predicted ratio at 1000 ft, assuming mean groundwater velocity of 0.6 ft/day, reaction half-life of 2 years, and 0.2 mole DCE produced from each mole of TCA.

  40. Principal Component Analysis and Reductive Dehalogenation Median = 77% Median = 58% Median = 74% • Results of PCA • Variance dominated by a single factor - GW flow regime? • Effect of reductive dehalogenation is apparent. • Results are independent of grouping strategy, i.e. no correlation with: • No. of CVOCs • No. of samples No. of sites No. of sites

  41. Principal Component Analysis and Temporal Trends = site with evidence of reductive dehalogenation 26 sites

  42. Implications • Can historical case data be used to predict plume behavior? • Yes: Signals (i.e., expected patterns of plume behavior) can be detected through site-specific noise (i.e., heterogeneities, different disposal histories).

  43. Implications • What are the key uncertainties associated with evaluating CVOC plume behavior using historical case data and what types of data are needed? • Ranges of groundwater velocities at sites (i.e., multiple pumping tests). • Geochemical indicator data (redox indicators, total soil organic carbon).

  44. Implications • How may CVOC historical case analysis be used in CVOC cleanup decision-making? • Reference frame for comparative analyses of plumes at individual sites. • A set of bounds for typical plume behavior - GIS applications? • Prioritization of characterization and remediation. • Actuarial data for insurance on monitored natural attenuation.

  45. Basic CVOC Plume Metrics*compared to 1995 LLNL LUFT Study • Change in Plume Length, minimum 3 yrs of data. • 29% increasing plume length (8%) • 16% decreasing plume length (33%) • 55% no statistically significant trend (59%) • Median length 1660 ft (130 ft) 90% less than 6300 ft (306 ft) (*Based on a review of 247 CVOC plumes from 65 sites)

  46. San Francisco Bay Area Silicon Valley – About 125 CVOC Plumes including 24 Superfund Sites San Francisco

  47. Non-Fuel Program:S.F. Bay Regional Water Quality Control Board There are nearly 600 significant non-fuel cases ranging from Superfund to small dry cleaners (not counting about 900 lower-risk sites) • 65% have undertaken source control measures. This includes soil excavation and disposal/treatment, soil venting, soil vapor extraction, free product removal • About 36% have active groundwater cleanup in progress. This includes pump and treat systems, sparging, enhanced biodegradation, and innovative methods • About 13% have other engineering controls including capping and containment barriers

  48. Overview • Study produces the first ever statistical analysis of data from CVOC sites. • More variability than LUFT sites. • Don’t look for major changes compared to LLNL LUFT Study. • Look for states, rather than authors, to recommend regulatory response. • Follow-up analysis to confirm results will likely be needed to increase acceptance.

  49. Potential Regulatory Response #1 • Finding: Unlike Lawrence Livermore 1995 LUFT Study, CVOC plumes show wide variability. • Response: Unlikely to see any “global” regulatory changes.

  50. Potential Regulatory Response #2 - Plume Length • Finding: Reductive dehalogenation has less impact on plume length than source strength and groundwater velocity. • Potential Regulatory Response: Plumes with lower source strength and groundwater velocity may be better candidates for reductive dehalogenation - monitored natural attenuation remedies.

More Related