Plume Stability Analysis

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1 Groundwater Contaminant Plume Stability Analysis Joe A. Ricker, P.E. A member of the Earth Consulting Group, Inc. family of companies

2 Ricker Plume Stability Analysis Background Ricker Plume Stability Analysis Methodology Eample Site Analyses

3 Plume Stability MDNR Appendi H Definition Stable Groundwater Plume: a groundwater plume is stable when data representative of the entirety of the plume demonstrates that the plume is not epanding and that, overall, concentrations of chemicals of concern (COC) are not increasing. Shrinking Groundwater Plume: A groundwater plume is shrinking when data demonstrates that the areal etent of the plume is decreasing and concentrations of COCs, overall, are decreasing. Epanding Groundwater Plume: A groundwater plume is epanding when either the physical etent of the plume is increasing or concentrations of COCs are increasing.

4 Plume Stability A condition where the plume is no longer epanding in size, AND the plume footprint is not moving. Plume is at dynamic equilibrium Rate of chemical mass into the plume is equal to the rate of chemical mass lost from the plume

5 Why Evaluate Plume Stability? An increasing plume could migrate to sensitive receptors Evaluate remedial progress Answer Environmental Indicator Code (EI) CA 750 Has the migration of contaminated groundwater stabilized? Primary line of evidence when implementing MNA Historical groundwater data that demonstrate a clear and meaningful trend of decreasing contaminant mass and/or concentration over time - USEPA OSWER Directive P Demonstrate low risk to close sites

6 How is Plume Stability Determined? Qualitative Methods Concentration vs. Time Plots Concentration vs. Distance Plots Concentration Isopleth Maps Statistical Methods Well by well trend analysis Mann-Kendall Linear Regression Plume-Based Methods Plume Area Plume Mass Plume Center of Mass (COM) Mass Flu

7 How is Plume Stability Determined? Qualitative Methods Probability of Significant Risk Plume Stability Analysis Method High Moderate Low Concentration vs. Time Plots Trends in most wells visually stable and/or increasing Concentration vs. Distance Plots Moderate or no visual decrease in concentration along the plume centerline and generally stable trends in plots over time. Sentinel wells above DRCLs. Concentration Isopleth Maps Generally increasing plume size over time. Sentinel wells above DRCLs. No discernable trends in many wells, trends in some relevant wells Moderate visual decrease in concentration along the plume centerline and generally stable trends in plots over time. Sentinel Relatively unchanged plume size and etent over time. Sentinel wells with less than Trends in all relevant wells visually decreasing Significant visual decrease in concentration along the plume centerline and general decreasing trends in plots over time. Sentinel wells with nondetects. Discernable decrease in plume size and etent over time. Sentinel wells with nondetects.

8 How is Plume Stability Determined? Statistical Methods Probability of Significant Risk Plume Stability Analysis Method High Moderate Low Mann-Kendall Linear Regression Concentrations trends in any relevant monitoring wells are statistically Increasing or Probably Increasing Concentration trends in all relevant monitoring wells are statistically Decreasing, Probably Concentration trends in all relevant monitoring wells are statistically Decreasing or Probably Decreasing Mann-Kendall Trend Analysis Criteria Linear Regression Trend Analysis Criteria Mann-Kendal Confidence in Concentration Trend Ln Slope Statistic Trend Confidence in Trend Positive Negative S>0 > 95 % Increasing COV < 1 Stable < 90% No Trend S> % Probably Increasing COV > 1 No Trend S>0 < 90 % No Trend Probably Probably % S<0 < 90% and COV > 1 No Trend Increasing Decreasing S<0 < 90% and COV < 1 Stable > 95 % Increasing Decreasing S< % Probably Decreasing S< Decreasing

9 How is Plume Stability Determined? Plume-Based Methods Probability of Significant Risk Plume Stability Analysis Method High Moderate Low Plume Area Increasing or probably increasing trend in plume area. Stable trend in plume area. Decreasing or probably decreasing trend in plume area. Plume Mass Increasing or probably increasing trend in plume mass. Stable trend in plume mass. Decreasing or probably decreasing trend in plume mass. Plume Center of Mass (COM) Increasing or probably increasing trend in COM location. Condition should be verified with visual analysis to verify that plume is truly Mass Flu Increasing or probably increasing trend in mass flu at any transect location. Stable trend in plume COM location. Decreasing, probably decreasing, or stable trend in mass flu at each transect. Decreasing or probably decreasing trend in plume COM location. Decreasing or probably decreasing trend in mass flu at each transect.

10 Plume Stability - Eisting Methods Most Common Method to Evaluate Plume Stability Well by well trend analysis The primary concern in a stability demonstration is whether COC concentrations are increasing or decreasing at individual monitoring wells. - Indiana RISC Technical Guide Appendi 3 a stable or shrinking condition can be identified by a stable or decreasing concentration trends over time. For this analysis, an overall plume condition was determined for each COC based on a statistical trend analysis of concentrations at each well - AFCEE MAROS User s Guide

11 Plume Stability - Eisting Methods

12 Plume Stability - Eisting Methods

13 Plume Stability - Eisting Methods 100,000 Naphthalene Plume 52 Wells 10,000 1, Concentration (µg/l) DB-18 DB DB-22 DB-25 DB-27 DB-28 1 Year

14 Plume Stability - Eisting Methods Other Common Method to Evaluate Plume Stability Evaluate plume contours over time One method of evaluating plume status is to plot plume concentrations from four or more events on the same figure. - Washington Guidance on Remediation by Natural Attenuation

15 Plume Stability - Eisting Methods From State of Washington Guidance on Remediation of Petroleum-Contaminated Ground Water By Natural Attenuation (Publication No [Version 1.0])

16 Plume Stability - Eisting Methods Intermediate Aquifer Zone MW-19 VCCP-02 MW-02 MW-05 MW-20 TW Carbon Tetrachloride Plume Area MW MW-17 MW-15 TW-02 MW-03 MW-01 MW-14 MW-08 R² = Area (Acres) MW-04 0 TW-04 MW-06 VCCP Date MW-16 MW-18

17 Plume Stability - Eisting Methods 16,000 Carbon Tetrachloride Plume Average Concentration 14,000 12,000 10,000 8,000 R² = ,000 4,000 Concentration (µg/ l) 2, Date 45,000 Carbon Tetrachloride Plume Mass 40,000 35,000 30,000 25,000 20,000 15,000 R² = 0.58 Mass (lbs) 10,000 5, Date

18 Plume Stability - Eisting Methods 1993 PCP Plume 2008 PCP Plume River River AB-9D AB-17D AB-9D AB-17D PCP Conc. (ppb) PCP Conc. (ppb) 1000 Plume Boundary = 1 ug/l 1000 Plume Boundary = 1 ug/l AB-15D AB-15D CENTER OF MASS CENTER OF MASS 1 1 AB-13D AB-13D AB-8D OW-2A AB-3D TDOT Facility AB-20D AB-3D AB-21D TDOT Facility AB-20D AB-19D AB-8D OW-2A AB-21D AB-19D PCP Plume Evaluation Plume Area: 35.1 Acres Plume Average Concentration: 92.5 ug/l Plume Mass: 86.0 Pounds Site PCP Plume Evaluation Plume Area: 29.0 Acres Plume Average Concentration: 9.6 ug/l Plume Mass: 7.4 Pounds Site AB-1S AB-1S ,200 SCALE: 1 INCH = 600 FEET ,200 SCALE: 1 INCH = 600 FEET

19 Plume Stability - Eisting Methods 1,800 PCP Plume 11 Wells 1,600 1,400 1,200 DECREASING TREND AB-13D AB-19D AB-20D AB-21D 1, STABLE TREND Concentration (µg/ l) 600 INCREASING TREND DECREASING TREND Date

20 Plume Stability - Eisting Methods 40 PCP Plume Area Trend R² = Area (Acres) 5 0 Oct-92 Jan-94 Apr-95 Jul-96 Sep-97 Dec-98 Mar-00 Jun-01 Sep-02 Nov-03 Feb-05 May-06 Aug-07 Oct-08 Date

21 Plume Stability - Eisting Methods 100 PCP Plume Average Concentration Trend R² = 0.48 Oct-92 Jan-94 Apr-95 Jul-96 Sep-97 Dec-98 Mar-00 Jun-01 Sep-02 Nov-03 Feb-05 May-06 Aug-07 Oct-08 Average Concentration (µg/ l) Date 100 PCP Plume MassTrend R² = Oct-92 Jan-94 Apr-95 Jul-96 Sep-97 Dec-98 Mar-00 Jun-01 Sep-02 Nov-03 Feb-05 May-06 Aug-07 Oct-08 Mass (lbs) Date

22 Ricker Plume Stability Analysis Method Effective method to evaluate trends in plume characteristics using visual and statistical methods. Area Average concentration Mass Location of plume center of mass Mass Flu Efficiently assimilates large volume of historical data into concise and meaningful analysis

23 Ricker Plume Stability Analysis Method Ecellent groundwater management tool Termination of remediation systems where low risk is demonstrated Basis for MNA Monitor progress of remediation system Ricker Method Highlighted by USEPA Region IV RCRA Showcase Pilot Methodology published in Groundwater Monitoring & Remediation 28, no. 4/ Fall 2008/pages 85 94

24 Dry Dock 1 Dry Dock 2 Ricker Plume Stability Analysis Method Methodology Selection of indicator compound(s) Develop concentration isopleth maps Each indicator compound Each aquifer level (shallow, deep, etc.) Plume boundary defined by MCL or site-specific level MW-19 MW-17 MW-18 DIESEL RECON FACILITY MW-16 [18,300] MW-20 [10.1] TW-03 (7,790) MW-15 [160,000] TW-02 (66,000) TW-04 (61,300) MW-03 MW-14 [69,600] MW-08 [16,100] MW-04 [19,805**] MW-06 [86.2] MW-02 [ND**] MW-12 VCCP-01 [ND*] VCCP-02 [ND*] MW-01 [161**] MW-05 MW-12 MW-27 [NS-22] MW-8 MW-32 [NS-13] MW-4 MW-11 MW-20 MW-9 MW-10 MW-6 [140] MW-28 [23] MW-26 [NS-110] MW-3 MW-7 [ND-6.8] DMW-1 [0.38] DMW-2 MW-13 MW-14 [140] [0.41] SG-13 MW-29 [8.9] CFMW-9 CFMW-8 MW-25 [NS-1.7] CFMW-1 [12,000] MW-18 MW-31 [NS-78] MW-5 [ND-34] MW-23 [3,900] CFMW-3 [20,000] MW-17 [2,500] DMW-3 MW-15 MW-19 CFMW-4 [140,000] CFMW-2 [12,000] DMW-4 MW-21 [12,000] [NS-6,600] MW-22 [NS-11,000] MW-2 [NS-0] CFMW-6 [3,700] CFMW-12 CFMW-7 [820] MW-30 MW-24 [NS-1,000] MW-1 [NS-0] MW-16 CFMW-11 WW-3 MW-4 Gas Front Office MW-6 MW-3 MW-15D Tank Farm #400 MW-15S MW-14 [49.5] DW-6 MW-12 [156] Tank Farm #500 Tank Farm #300 MW-2 [7.52] DW-3 RW-1 [130] DW-4 DW-1 Drum Storage Bldg. MW-17D Tank Farm #600 Boiler Room Sump 2R MW-11 [60.5] Tank Farm #100 MW-17S [NS-69.6] Sump 3 General Groundwater Flow MW-1A [0.032] Tank Farm #200 MW-8 MW-16 Property Boundary DW-5 WW-1 DW-2 MW-5 [0.037] MW-10 MW-7 Operations Office Earthen Berm Wastewater Treatment Plant Dock 3 Dock 2 Dock 1 Dock 4 Dock 5 River Estimated Historical Limits of Former Surface Impoundment

25 Dry Dock 1 Dry Dock 2 Ricker Plume Stability Analysis Method Methodology Calculate plume stability characteristics Area Average concentration Mass Center of mass MW-19 MW-20 [10.1] TW-03 (7,790) MW-02 [ND**] MW-12 VCCP-02 [ND*] MW-05 MW-8 MW-4 MW-9 MW-10 MW-3 CFMW-9 CFMW-8 CFMW-3 [20,000] CFMW-4 [140,000] CFMW-6 [3,700] CFMW-12 CFMW-7 [820] MW-16 CFMW-11 MW-17 MW-16 [18,300] MW-15 [160,000] TW-02 (66,000) TW-04 (61,300) MW-03 MW-14 [69,600] MW-08 [16,100] MW-04 [19,805**] MW-06 [86.2] VCCP-01 [ND*] MW-01 [161**] MW-12 MW-32 [NS-13] MW-27 [NS-22] MW-11 MW-6 [140] MW-28 [23] MW-26 [NS-110] MW-7 [ND-6.8] DMW-1 [0.38] DMW-2 MW-13 MW-14 [140] [0.41] MW-25 [NS-1.7] CFMW-1 [12,000] MW-18 MW-31 [NS-78] MW-5 [ND-34] MW-23 [3,900] MW-17 [2,500] MW-19 CFMW-2 [12,000] DMW-4 MW-21 [12,000] [NS-6,600] MW-22 [NS-11,000] MW-2 [NS-0] MW-30 MW-24 [NS-1,000] MW-1 [NS-0] General Groundwater Flow MW-20 MW-18 DIESEL RECON FACILITY DMW-3 MW-15 SG-13 MW-29 [8.9] Property Boundary DW-4 WW-3 Wastewater Treatment Plant MW-8 DW-5 MW-7 MW-4 Gas Tank Farm MW-3 Front #400 Office Tank Farm #600 MW-16 MW-15D MW-15S Tank Farm #500 MW-6 MW-14 [49.5] DW-6 MW-12 [156] Boiler Room Tank Farm Sump 2R #300 MW-11 [60.5] MW-2 Tank Farm [7.52] #100 DW-1 MW-5 [0.037] Tank Farm WW-1 #200 DW-3 Sump 3 Estimated Historical Limits of Former Surface Drum Impoundment Storage RW-1 Bldg. [130] MW-17S MW-17D [NS-69.6] DW-2 MW-10 Dock 1 MW-1A [0.032] Operations Office Earthen Berm Dock 3 Dock 2 Intermediate Plume Evaluation Plume Area: 149 Acres Plume Average Concentration: 9,399 ug/l Plume Mass: 23,832 Pounds Plume Evaluation Plume Area: 19.8 Acres Plume Average Concentration: 5,610 ug/l Plume Mass: 1,512 Pounds Dock 4 CVOC Plume Evaluation Plume Area: 4.9 Acres Plume Average Concentration: 19.5 mg/l Plume Mass: 1,615 Pounds Dock 5 River

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