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Section 4- Characterization
Characterization is 95% of the Success of ISCO Develop a complete and comprehensive
Conceptual Site Model ISCO is a Mass Destruction Technology Successful Treatment must Identify both target
and non target analytes and contain all phases of Mass
Know Flow paths within soil Structure
2
Conceptual Site Model Development
Characterization of nature and mass of contaminants present• Sorbed• Dissolved• Free product phases
Subsurface geology, site topography, aquifer geochemistry
Identification of major migration pathways for contaminants of concern (COC)• Surface and subsurface structures• Underground utilities
Direction / gradient / velocity of groundwater flow Surface water features / uses, and potential receptors in
the area
First and most important step in remediation project includes
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•
Contaminant MassPSH, Sorbed, Dissolved
Appl. Well
Existing MW Number of Wells
Total VOCs (average for all Areas) ppm 850
Area 1 - 100x75 10
TIC ppm 0Area 2 - 300x130 (includes Area 1) 35
TPH/Cosolvents ppm 0 Area 3 - 185x 125 20
Multiply the number of wells times the reagent requirement
Total Contaminant Load ppm 850
4
Contamination mass exists in four phases in the contaminated zone• Soil gas
• Sorbed
• Dissolved
• Non-aqueous phase liquid (NAPL) or phase-separated
Geochemistry, partitioning coefficient (Kow) determines the relationship between phases in the saturated zone
Majority of mass (normally >80%) is sorbed and phase-separated
Total Mass EvaluationNature of Contamination
Graphic source: Suthersan, 1996
5Total Mass EvaluationImportance of Mass Calculations
Evaluate pre- and post- total contaminant mass
Sorbed and non-aqueous phase mass converts to dissolved during treatment and until site reaches post treatment final equilibrium
Possible “rebound” causes• Dissolution of sorbed or non-aqueous phase
• Inadequate site characterization
• Change in groundwater flow direction
Decrease in total mass may not be reflected in short-term dissolved concentrations Electroconductivity
Diagram
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•
Treatment Volume Estimate
CleanOX Appl. Well
Existing MW
Radius of Influence ft 20
Area of Influence sft 1258
Screen Depth, top ft 5
Screen Depth, bot. ft 30
Total Treatment Volume cft 31450
Total Groundwater Volume gal 70583
Total Groundwater Weight lb 588744
7Value of Data Quantity vs. Certified Analytical Data
ISCO requires contaminant delineation, precise concentration data quality not as critical as for closure confirmation
References – available at www.itrcweb.org under “Guidance Documents”• ITRC Technical and Regulatory Guidance for the Triad
Approach: A New Paradigm for Environmental Project Management (SCM-1, December 2003)
• ITRC Strategies for Monitoring the Performance of DNAPL Source Zone Remedies (DNAPLs-5, August 2004)
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•
Site Geochemistry/Geology
Site Geochemistry/Geology Units ValueRange Limits Notes
Porosity % 0.3
Permeability md 3574.237 1 - 10,000
pH s.u. 6.5 <8.5
Specific conductance uS/cm 500 100 - 6000
Groundwater temperature 0F 65 32 - 130
Groundwater velocity ft/day 0.020.0001 -
0.2
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Oxidant Demand Nomenclature
Natural oxidant demand (NOD) Soil oxidant demand (SOD) Total oxidant demand (TOD) Natural organic matter (NOM) Standard laboratory measurements of oxidizable
matter in groundwater include• Chemical oxygen demand (COD)
• Total organic carbon (TOC)
• Total inorganic carbon (TIC)
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•
Site Geochemistry/Geology
Site Geochemistry/Geology Units Value Range Limits Notes
Redox potential (ORP) mV 0 70 - (-70)
Grain size mm 0.07 10% pt.
Dissolved oxygen (DO) ppm 4 0.01 - 25
TDS ppm 500 50 - 1500
TOC in groundwater ppm 4 <40
Hydroxyl scavenger ppm 100 <400
Well diameter inch 11/2 new SS
11Conditions that Require Special Consideration
Low permeable soils Deep aquifers LNAPL/DNAPL Confined formations Swamps or high organic soils Old landfills and dumps River embankments Under buildings
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Surface Water Body
Pipeline
I-55 Limited Access Highway
Private PropertyAccess Only
No Utilities
Flood Prone Area with Dirt Roads
Special Site Model Considerations
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Lithology and Flow Path
Borings need to be properly installed by experienced personnel, which is contrary to reimbursement program pricing
Fine Sand lenses and variations in permeability are difficult to determine with Geoprobe programs
Wells need to be properly screened and developed (not three well volumes as in PST programs)
Confining layers are critical
14Conceptual Site ModelTarget Interval Identification
Target Interval
Contaminant MassSoil
Conductivity