A Hydrostratigraphic and Geochemical Data-driven Approach to the Development of a CSM for the Analysis and Selection of Remedial Options at a FCSAP DNAPL Site Federal Contaminated Sites National Workshop 2016 Stantec Consulting Ltd. April 2016
Agenda 1 Background 2 Study Objective 3 Conceptual Site Model (CSM) –Development Methodology 4 CSM - Results
1 Background The facility is currently used as a refinishing facility, which was constructed in stages between 2009 and 2012.
Background • During the facility inception, subsurface impacts were observed in building excavations during construction. • In order to address the observed impacts, approximately 3,242 tonnes of solvent impacted soil and 1,363,054 litres of solvent impacted groundwater were removed for off-site disposal.
Background • Additional subsurface investigations completed within the vicinity of facility resulted in expanding the boundary of groundwater impacts to the north and south of the facility (Site). • The Site and surrounding area (Study Area) is comprised of unconsolidated fill and native glaciolacustrine or glacial deposits overlying the Paleozoic bedrock.
Background • The primary contaminants of concern (COC) within the Study Area groundwater are Chlorinated Volatile Organic Compounds (CVOCs). • Impacted media include soil, groundwater, and soil vapour.
2 Study Objective A CSM capable of generating quantitative information for the analysis and selection of optimal remedial options was developed.
Study Objective • A typical CSM is limited to the qualitative presentation of contaminated site characteristics (e.g., illustration or cartoon). • The CSM development process often does not provide sufficient quantitative information (e.g., mass discharge estimates, remediation time frames) to perform a robust analysis critical to the selection of remedial options.
Study Objective • A CSM that generates quantitative information for the analysis and selection of optimal remedial options was developed.
3 CSM – Development Methodology A stepwise approach was used to develop the CSM for the Study Area, involving geospatial integration of geological, hydrogeological, geochemical, and site characterization datasets.
CSM - Development Methodology
CSM - Development Methodology
CSM - Development Methodology
CSM - Development Methodology
CSM - Development Methodology
CSM - Development Methodology
4 CSM - Results The quantitative information (e.g., estimates of contaminant mass and discharge rates by each hydrostratigraphic unit) derived during the CSM development process allowed for the identification of hydrostratigraphic units where enhanced passive or active remediation will be required.
CSM - Geological Setting
CSM – Conceptual Geological Model Elevation Major Soil or Bedrock Conceptual Geological Geological Description USCS Symbols (m AMSL) Classification Group Units for the Site + 89 Topsoil, fill, asphalt Non-native Not Applicable (NA) Fill Coarse and Fine grained Glaciolacustrine deposit SP, SP-SM, SM, ML Shallow Overburden Unit deposits Glacial Till or Diamicton (poorly sorted Coarse grained deposits GP, GW, GM, SP, SP Till unconsolidated sediment) Fractured Bedrock (RQD 1 NA values <70) Fractured to sound Paleozoic bedrock of bedrock Verulam Formation Sound Bedrock NA (RQD 1 values ≥ 70) + 76 Notes: 1 Rock Quality Designation (RQD) values expressed in percentage
CSM – Hydrogeological Model
CSM - Groundwater Flow
CSM – Potential TCE Source Areas in Soil Average Soil Dry Density Surficial Thickness /Bedrock of Soil Bulk TCE Estimated Hydrostratigraphic Extent of Volume /Bedrock of Retention Volume TCE mass Potential Units /Lithology Source (m 3 ) Unit Capacity 1 (m 3 ) 2 (kg) Source Source Area (m 2 ) (kg/m 3 ) Area Area (m) Interface Aquifer – 320 2.76 883.2 0.005 4.42 1937 8561 Source Glacial Till Area “A” Interface Aquifer – Source 320 0.79 252.8 0.0002 0.05 1427 71 Fractured Bedrock Area “A” Total Estimated TCE Mass in the Interpreted Potential Source Area “A” 8632 Interface Aquifer – 1830 0.26 475.8 0.005 2.38 1937 4610 Source Glacial Till Area “B” Interface Aquifer – 1830 3.49 6386.7 0.0002 1.28 1427 1826 Source Fractured Bedrock Area “B” Total Estimated TCE Mass in the Interpreted Potential Source Area “B” 6436 Notes: 1 In the fractured media, the bulk retention capacity can be in the range of 0.0002 to 0.002 (UK EA, 2003). Fractured media cannot retain as much DNAPL per unit volume as unconsolidated deposits. In unconsolidated deposits (i.e., glacial till) can be in the range of 0.005 to 0.03 (UK EA, 2003). 2 Estimate based on information obtained from SSI#3 (December 2014).
CSM – Contaminant Mass in Groundwater Estimates of Groundwater Volumes with Groundwater Hydrostratigraphic Concentrations ≥ Remediation Target Levels Chemical Units (m 3 ) Dichloroethene, cis-1,2- 0 Dichloroethene, trans-1,2- Shallow 0 overburden unit Trichloroethene 0 Vinyl chloride 0 Total for the Shallow Overburden Unit 0 34,100 Dichloroethene, cis-1,2- 0 Dichloroethene, trans-1,2- Interface Aquifer 120,000 Trichloroethene 67,500 Vinyl chloride Total for the Interface Aquifer 221,600 Dichloroethene, cis-1,2- 0 Dichloroethene, trans-1,2- 0 Sound Bedrock Trichloroethene 18,800 Vinyl chloride 0 Total for the Sound Bedrock 18,800
CSM – Conceptual Geochemical Model Major Soil or Elevation Conceptual Conceptual Bedrock Geological USCS Hydrogeological Geochemical (m Geological Hydrostratigraphic Classification Description Symbols Setting AMSL) Units Units Setting Group + 89 Not Topsoil, fill, Non-native Applicable Fill Unsaturated Zone asphalt (NA) Largely aerobic Faster Flow with large sub- Coarse and Shallow Glaciolacustrine SP, SP-SM, Shallow Regime with oxic and Fine grained Overburden deposit SM, ML Overburden Unit significant anaerobic deposits Unit heterogeneities zones Glacial Till or Coarse Diamicton GP, GW, grained (poorly sorted Till Largely GM, SP, SP Faster Flow deposits unconsolidated anaerobic with Regime with sediment) Interface Aquifer pockets of significant Fractured aerobic and heterogeneities Bedrock sub-oxic zones NA (RQD 1 Paleozoic Fractured to values <70) bedrock of sound Verulam Sound bedrock Predominantly Formation Bedrock Sound Bedrock Simple, slower NA anaerobic (RQD 1 Aquifer flow regime values ≥ 70) + 76 Notes: 1 Rock Quality Designation (RQD) values expressed in percentage
CSM – Sustainability of Biologically Mediated Dechlorination – Dissolved Phase Plume in Groundwater (Interface Aquifer) Carbon Donor Mass of TCE Daughter Available Donor (Kg-H2 equivalent) to Sustainability of MNA Products 2 Mass 3 Location CVOC (kg –H 2 equivalent) (kg –H 2 equivalent) (Kg-H2 equivalent) Ratio 1 Unlikely, available Dissolved Phase Plume donor mass < donor in groundwater demand from 0.01 6.24 0.05 (CVOC concentrations competing electron above the RTLS) acceptors (267 kg- H 2 /yr) Notes: 1 Mass of BTEX (carbon donor) compared to mass of CVOC (TCE, cis-1, 2-DCE, Vinyl Chloride) estimated based on December 2014 groundwater sampling results. 2 Estimated mass of BTEX in the source area based on December 2014 sampling results. 3 Available donor mass (kg-H 2 ) = Carbon Donor to CVOC ratio x Mass of Carbon Donor required for the Dechlorination of TCE
Conceptual Site Model A A’
Conceptual Site Model B’ B
Contributors/Collaborators: Sonny Sundaram, Ph.D, P.Geo. Jean Philippe Gobeil, M.Sc. Marc Bouchard, P.Eng. David Wilson, M.A.Sc., P.Eng. Stantec Ottawa
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