Groundwater Contaminant Plume Stability …

1 Groundwater Contaminant Plume Stability AnalysisJoe A. Ricker, A member of the Earth Consulting Group, Inc. family of companiesRicker Plume Stability Analysis Background Ricker Plume Stability Analysis Methodology Example Site AnalysesPlume Stability MDNR Appendix 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 expanding 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 extent of the Plume is decreasing and concentrations of COCs, overall, are decreasing. Expanding Groundwater Plume : A Groundwater Plume is expanding when either the physical extent of the Plume is increasing or concentrations of COCs are Stability A condition where the Plume is no longer expanding in size, AND the Plume footprint is not moving.

2 Plume is at dynamic equilibrium Rate of chemical mass into the Plume is equal to the rate of chemical mass lost from the plumeWhy 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 Demonstrate low risk to close sites-USEPA OSWER Directive 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 FluxHow is Plume Stability Determined?

3 Qualitative MethodsPlume Stability Analysis MethodHighModerateLowConcentration vs. Time Plots Trends in most wells visually stable and/or increasingNo discernable trends in many wells, trends in some relevant wells Trends in all relevant wells visually decreasingConcentration 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 visual decrease in concentration along the Plume centerline and generally stable trends in plots over time. Sentinel Significant visual decrease in concentration along the Plume centerline and general decreasing trends in plots over time. Sentinel wells with Isopleth Maps Generally increasing Plume size over time. Sentinel wells above unchanged Plume size and extent over time. Sentinel wells with less than Discernable decrease in Plume size and extent over time.

4 Sentinel wells with of Significant RiskHow is Plume Stability Determined? Statistical MethodsPlume Stability Analysis MethodHighModerateLowMann-KendallLinear RegressionProbability of Significant RiskConcentrations trends in any relevant monitoring wells are statisticallyIncreasing or Probably IncreasingConcentration trends in all relevant monitoring wells are statisticallyDecreasing, Probably Concentration trends in all relevant monitoring wells are statisticallyDecreasing or Probably DecreasingMann-Kendall Trend Analysis CriteriaLinear Regression Trend Analysis CriteriaMann-KendalConfidence in Concentration Trend Statistic TrendConfidence in Trend Positive Negative S>0 > 95 % Increasing COV < 1 StableS>0 90-95 % Probably Increasing COV > 1 No Trend S>0 < 90 % No Trend ProbablyProbablyS<0 < 90% and COV > 1 No Trend Increasing Decreasing S<0 < 90% and COV < 1 Stable > 95 % Increasing Decreasing S<0 90-95 % Probably Decreasing S<0 Slope< 90% No Trend 90-95 % How is Plume Stability Determined?

5 Plume -Based MethodsPlume Stability Analysis MethodHighModerateLowPlume AreaIncreasing or probably increasing trend in Plume trend in Plume or probably decreasing trend in Plume MassIncreasing or probably increasing trend in Plume trend in Plume or probably decreasing trend in 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 Stable trend in Plume COM or probably decreasing trend in Plume COM FluxIncreasing or probably increasing trend in mass flux at any transect , probably decreasing, or stable trend in mass flux at each or probably decreasing trend in mass flux at each of Significant RiskPlume Stability - Existing 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.

6 A stable or shrinking condition can be identified by a stable ordecreasing concentration trends over time. For this analysis, anoverall Plume condition was determined for each COC based on a statistical trend analysis of concentrations at each - Indiana RISC Technical Guide Appendix 3- AFCEE MAROS User s GuidePlume Stability - Existing MethodsPlume Stability - Existing MethodsPlume Stability - Existing Methods Naphthalene Plume 52 Wells1101001,00010,000100,000 Concentration ( g/l)YearDB-18DB-21DB-22DB-25DB-27DB-28 Plume Stability - Existing 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 AttenuationPlume Stability - Existing MethodsFrom State of Washington Guidance on Remediation of Petroleum-Contaminated Ground Water By Natural Attenuation (Publication No.)

7 05-09-091 [Version ]) Plume Stability - Existing MethodsTW-02TW-03TW-04MW-01MW-02MW-04MW- 05MW-06MW-08MW-12MW-14MW-15MW-16MW-17MW- 18MW-19 VCCP-01 VCCP-02MW-03MW-20 Intermediate Aquifer ZoneR = (Acres)DateCarbon Tetrachloride Plume AreaPlume Stability - Existing MethodsR = ,0004,0006,0008,00010,00012,00014,00016, 0001997199819992001200220042005200620082 009 Concentration ( g/ l)DateCarbon Tetrachloride Plume Average ConcentrationR = ,00010,00015,00020,00025,00030,00035,000 40,00045,0001997199819992001200220042005 200620082009 Mass (lbs)DateCarbon Tetrachloride Plume MassPlume Stability - Existing MethodsxxxxxxxxxxxxxxxxxxxxAB-3 DAB-8 DAB-9 DAB-15 DAB-20 DAB-1 SOW-2 AAB-13 DAB-17 DAB-19 DAB-21 DSCALE: 1 INCH = 600 FEET0 300 600 900 1,200 RiverTDOT FacilitySitePlume Boundary = 1 ug/LPCP Plume EvaluationPlume Area: AcresPlume Average Concentration: ug/lPlume Mass: Pounds15501005001000 PCP Conc.

8 (ppb)CENTER OF MASS1993 PCP Plume2008 PCP PlumexxxxxxxxxxxxxxxxxxxxAB-3 DAB-8 DAB-9 DAB-15 DAB-20 DAB-1 SOW-2 AAB-13 DAB-17 DAB-19 DAB-21 DSCALE: 1 INCH = 600 FEET0 300 600 900 1,200 RiverTDOT FacilitySitePlume Boundary = 1 ug/LPCP Plume EvaluationPlume Area: AcresPlume Average Concentration: ug/lPlume Mass: Pounds15501005001000 PCP Conc.(ppb)CENTER OF MASSP lume Stability - Existing Methods PCP Plume 11 Wells02004006008001,0001,2001,4001,6001, 8001993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Concentration ( g/ l)DateAB-13 DAB-19 DAB-20 DAB-21 DDECREASINGTRENDDECREASINGTRENDSTABLE TRENDINCREASINGTRENDP lume Stability - Existing MethodsR = 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 Area (Acres)DatePCP Plume Area TrendPlume Stability - Existing MethodsR = 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 ( g/ l)DatePCP Plume Average Concentration TrendR = 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)

9 DatePCP Plume MassTrendRicker 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 Flux Efficiently assimilates large volume of historical data into concise and meaningful analysisRicker Plume Stability Analysis Method Excellent 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 Ricker Plume Stability Analysis Method Methodology Selection of indicator compound(s) Develop concentration isopleth maps Each indicator compound Each aquifer level (shallow, deep, etc.)

10 Plume boundary defined by MCL or site-specific levelTW-02TW-03TW-04MW-01MW-02MW-04MW-05 MW-06MW-08MW-12MW-14MW-15MW-16MW-17MW-18 MW-19 VCCP-01 VCCP-02(66,000)(7,790)(61,300)[161**][ND **][19,805**][ND][ ][16,100][ND][69,600][160,000][18,300][N D][ND][ND][ND*][ND*][NS]MW-03[ ]MW-20 DIESELRECONFACILITYSG-13MW-1MW-2MW-4MW-8 MW-9MW-10MW-11MW-15MW-16MW-18MW-19MW-20M W-25MW-26MW-27MW-31MW-3MW-12MW-21MW-22MW -24MW-30MW-32 DMW-1 DMW-3 CFMW-1 CFMW-2 CFMW-3 CFMW-4 CFMW-6 CFMW-7 CFMW-8 CFMW-9 CFMW-11 CFMW-12MW-5MW-6MW-7MW-14MW-17MW-23MW-28M W-29[12,000][12,000][20,000][140,000][3, 700][820][ND][ND][ND][ND][NS-0][NS-0][NS ][ND-34][140][ ][NS][NS][NS][NS][ ][NS][NS][2,500][NS][NS][NS][3,900][ ][NS-110][NS-22][23][ ][NS-78][NS][NS][NS-6,600][NS-11,000][NS -1,000][NS][NS-13]General Groundwater FlowDMW-4 DMW-2MW-13[ND][140][ ][ND][NS][12,000]Sump 2 RSump 3MW-1 AMW-3MW-4MW-5MW-6MW-7MW-8MW-10MW-11MW-15 SMW-16MW-2MW-12MW-14MW-17 SRW-1DW-2DW-4MW-15 DDW-1DW-3DW-6MW-17D WW-1WW-3[ ][ ][ND][ND][ ][ND][ND][ND][ND][ ][156][ ][NS][NS][ ][130]