API DR 225 : 1998

REMEDIATION OF A FRACTURED CLAY TILL USING AIR FLUSHING: FIELD EXPERIMENTS AT SARNIA, ONTARIO

American Petroleum Institute

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Executive Summary
I. INTRODUCTION
      A. Background
      B. Objectives
      C. Experimental Approach
      D. Overview
II. OVERVIEW OF IN SITU REMEDIATION OF LOW-PERMEABILITY SOIL
III. DESCRIPTION OF THE SARNIA FIELD SITE
      A. Overview
      B. Site Geology
IV. CONCEPTUAL MODEL FOR LNAPL DISTRIBUTION IN A LOW-
      PERMEABILITY SOIL AND POTENTIAL IMPACT ON GROUNDWATER
      A. LNAPL Distribution
      B. Microbiological Activity
      C. Water Flow
      D. Air Flow
V. APPLICATION OF AIR FLUSHING TECHNOLOGIES IN LOW-
      PERMEABILITY SOILS
VI. EXPERIMENTAL SETUP AND TECHNIQUES
      A. Cell Construction
      B. Controlled Gasoline Release
      C. Vapor Extraction/Air Sparging System
         1. Vapor Monitoring and Air Sparging Well Design
         2. Trench Design
         3. Vertical Vapor Extraction Well Design
         4. Pumping Equipment
      D. Soil Vapor Monitoring and Analysis
      E. Soil Coring and Analysis
      F. Hydraulic Fracturing
      G. Microbiological Sampling and Analysis
      H. Water Levels Following the Gasoline Release
VII. DETERMINATION OF AIR PERMEABILITY AND EFFECTIVE POROSITY
VIII. SOIL VAPOR EXTRACTION FROM THE TRENCHES
      A. Pressure and Air Flow Measurements
      B. Hydrocarbon Recovery
         1. Mass Removal in Extracted Vapor
         2. Mass Removal in Extracted Water
      C. Water Levels and Soil Temperatures
IX. SOIL VAPOR EXTRACTION FROM VERTICAL WALLS
      A. Pressure and Air Flow Measurements
      B. Hydrocarbon Recovery
X. AIR SPARGING RESULTS
      A. Pressure and Air Flow Measurements
      B. Hydrocarbon Recovery
XI. EFFECTS OF HYDRAULIC FRACTURING
      A. Water Removal
      B. Hydrocarbon Recovery
XII. MASS BALANCE ANALYSIS
      A. Soil Core Analyses
         1. Pre-Remediation (July, 1993) Distribution of the
               Contaminants
         2. Post First Season (October, 1993) Distribution
               of the Contaminants
         3. Pre-Second Season (June, 1994) Distribution
               of the Contaminants
         4. Final Soil (June, 1995) Distribution of the
               Contaminants
       B. Biodegradation Measurements
XIII. VOLATILIZATION FLUX EXPERIMENTS
XIV. SUMMARY AND CONCLUSIONS
XV. REFERENCES
APPENDIX A: HYDRAULIC FRACTURING
APPENDIX B: BIODEGRADATION MEASUREMENTS
APPENDIX C: SOILS DATA
List of Tables
Table I. Chronology of events at the Sarnia site
Table II. Summary of soil characteristics
Table III. Base case parameters for the numerical diffusion model
Table IV. Composition and physical properties of the spilled
             hydrocarbons
Table V. Pneumatic pumping test measured flows and pressures
Table VI. Air permeabilities calculated from fracture aperture and
             spacing values
Table VII. Effective porosity tracer test calculated values
Table VIII. Breakthrough times for the SF6 tracer tests
Table IX. Estimated mass removed in the extracted water
Table X. Calculated mass recovery from air sparging
Table XI. Soil hydrocarbon mass (kg) estimated from the pre-
             remediation (July, 1993) soil cores
Table XII. Soil hydrocarbon mass (kg) estimated from the post first
             season (Oct., 1993) soil cores
Table XIII. Mass of hydrocarbons accounted for by soil core analysis
             and SVE/IAS
Table XIV. Soil hydrocarbon mass (kg) estimated from the pre-second
             season (June, 1994) soil cores
Table XV. Compound-specific mass (in grams) from soil analyses (OGI
             GC/MS) for all post remediation samples (June, 1995).
             depths are given in cm below ground surface
Table XVI. Compound-specific mass balance (in kg)
Table XVII. Compound-specific mass balance (in % of initial mass)
Table XVIII. Average percent remaining for each compound at the
             conclusion of the field experiments
Table XIX. Geochemical soil characteristics (ORNL, Appendix B)
Table XX. Microbial soil characteristics of the contaminated soil
             (cells/g)
Table XXI. Calculated and measured static headspace concentrations in
             the volatilization flux chamber
Table XXII. Static-mode (non-flushing mode) concentration data in the
             flux chamber
Table XXIII. Flow-through-mode fluxes
Table XXIV. Measured and calculated flux values for the vapor flux
             experiments
List of Example Calculations
Example Calculation 1. Total fracture porosity and soil volume
                        contaminated
Example Calculation 2. Estimated single-component NAPL dissolution
                        into soil matrix
Example Calculation 3. Calculation of mass of MTBE removed in the
                        water collected by the SVE system
Example Calculation 4. Air flow measurement using helium as a tracer
Example Calculation 5. Estimated total daily mass removal while
                        extracting the trenches
Example Calculation 6. Percent recovery of injected sparge air by the
                        SVE system
Example Calculation 7. Calculated initial concentration of pentane at
                        sample location S1-a based on the final
                        naphthalene data
Example Calculation 8. Estimated biodegradation rate based on
                        hydrocarbon recovery data

Abstract

Reports documents for a field study of the remediation of a clay soil (a fractured clay till) using air flushing technologies. This research was conducted using a model ''synthetic'' gasoline blend of known mass, volume and composition, unlike numerous other studies conducted at sites where the initial volume and composition of the spill were unknown. Gasoline released into a well-characterized natural soil within a 10 m by 10 m test cell contained by driven, interlocking sheet pilings was carried out. Canada, near Sarnia, Ontario, was used as the test site.