Those Stubborn Sterilants – Environmental Management of Sites Impacted with Bromacil, Dicamba and Tebuthiuron in Alberta

Remediation Technologies Symposium October 11, 2017

Barry Rakewich, P.Ag., EP Hans Bakker, P.Geo. Nichols Environmental (Canada) Ltd. Outline  Definitions  Bromacil, Dicamba, Tebuthiuron  Groundwater Contamination  Environmental Site Assessments  Phase I and II ESAs  Contaminated Sites Framework  Alberta Tier 1 Guidelines  Alberta Tier 2 Guidelines (pathway exclusion)  Risk Management – Exposure Control  Remediation  Case Studies  Questions??? Definitions

 Sterilants  Commonly used in oil and gas industry for vegetation management  Chemical that temporarily or permanently prevents all vegetative growth and must be registered as a herbicide…typically non-selective

 Pesticides  Substance used for controlling pests  Includes insecticides, fungicides and herbicides

 Herbicides  Chemical agent used to destroy or inhibit plant growth Definitions

 Selective vs Non-Selective  Selective herbicides control specific types of vegetation  Non-selective herbicides used for total vegetation control  Residual vs Non-Residual  Residual herbicides long term/either selective or non-selective  Non-residual herbicides last one growing season/either selective or non- selective

 Persistence  Continued or prolonged existence of herbicide  Related to half life, which is dependent on…  application rate, soil moisture, pH, temperature, OM content, structure,  chemistry, physical properties, composition, microbial content Definitions

 Mobility  Ability of a herbicide to move or be moved  Mainly influenced by adsorption coefficient and water solubility

 Adsorption Coefficient (Koc)  Measures how strongly chemical sorbs to soil vs what remains in solution

 ↑ Koc more likely to sorb to soil = less mobile

 ↓ Koc more likely to remain dissolved = more mobile  Water Solubility  Ability of a herbicide to dissolve in water (mg/L)  The higher the number, the more soluble the herbicide Groundwater Contamination

 Mobility and Persistence  Two main characteristics to determine likelihood of herbicide contaminating groundwater  Screening Methods  California Department of Pesticide Regulation (CDPR)  Gustafson (1988)  Leachability Index (LIX)  Degradation and Dissipation  Breakdown (degradation) or removal (dissipation) of a herbicide  Degradation is determined by half-life  Larger half life = longer timeframe for degradation  Dissipation occurs through volatilization, plant uptake, photo- decomposition, microbial-decomposition, adsorption Bromacil, Dicamba and Tebuthiuron Bromacil Dicamba Tebuthiuron Glyphosate First Registered 1963 1964 1973 1974

Common Trade Hyvar Banvel Spike Roundup Name Soil Half-life 14-1494 days 25 days 12-15 months 47 days

Water solubility ~807 mg/L ~4,500 mg/L ~2,500 mg/L 15,700 mg/L

Adsorption ~32 mL/g ~2 mL/g ~80 mL/g 24,000 mL/g

Coefficient (Koc) Persistence High Low-moderate High Low-moderate

Mobility Moderate High High Low

Occurrence Groundwater/ Groundwater/ Groundwater/ Soil/pore water pore water pore water pore water Primary Method Microbial Microbial Microbial Microbial of Natural Degradation Groundwater Contamination Groundwater Contamination Environmental Site Assessments

 Herbicide–impacted sites typically fall into three categories (Maurice, 1985)  Herbicide Spills/Releases  Herbicide Migration  Decommissioned Sites Environmental Site Assessments

 Herbicide Spills/Releases  Uncommon  Herbicide usually resides in top 15 cm of surface soil Environmental Site Assessments

 Herbicide Migration  Soil erosion due to runoff  High application rates  Sandy soil conditions  Poor site contouring  Spray drift Environmental Site Assessments

 Decommissioned Sites  Most common type of impacted sites and typically older  High application rates + several years of application  Herbicide migration to > 45 cm depth  Farms; transmission lines, oil & gas and industrial facilities; railways Phase I ESA

 Historical Review  Field Manual for Rehabilitating Soils Affected by Residual Herbicides (1995), information requirements:  Name of herbicide applicator;  Dates of applications;  Names of herbicides applied;  Application rates;  Details of other site activities;  Records of spills;  Details of construction activities; and  Records of previous remediation activities.

 Conduct interviews with former/current operators, landowners, herbicides applicators and adjacent landowners/operators Phase I ESA

 Aerial Photography  Monitor crop health over time  Emergence of UAVs = additional assessment information incl. current plant health, elevation mapping, site grading, evidence of spray drift Phase I ESA

 Site Inspection  Condition of vegetation on and off-site:  Stunted  Discoloured or dead  Bare ground  Site Contouring/drainage  Evidence of wind and/or water erosion  Sedimentation Phase II ESA

 Target APECs identified in the Phase I ESA  Background sample collection  sites surrounded by agricultural land  other facilities that have chemical vegetation management programs  Groundwater assessment  When a herbicide is highly persistent and mobile  Soil impacts below or near water table  Coarse-grained lithology / low organic content  Area of high precipitation and infiltration Phase II ESA

 Targeting APECs identified in the Phase I ESA  Regulatory evaluation  Are numerical guidelines < laboratory MDL  Bioassays may be required if numerical guidelines < laboratory MDL  Conceptual Site Model  Creating a CSM is EXTREMELY important  Identifies pathways, receptors and potential elimination of pathways. Contaminated Sites Framework

 Alberta Tier 1 Soil Guidelines - Bromacil

Receptor Human Ecological

Pathway Direct DUA Direct Soil Contact PFAL Livestock Water Irrigation Water Soil contact Soil Type Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse

Natural 7.0 10 0.20 0.12 0.009 0.009

Ag 2000 7.0 10 0.20 0.12 0.009 0.009 2.0 2.0 BDL BDL

Res/Park 2000 7.0 10 0.20 0.12 0.009 0.009

Comm 3500 7.0 10 0.49 0.20 0.009 0.009

Indust 15000 7.0 10 0.49 0.20 0.009 0.009

BDL = guideline below detection limit for irrigation water  groundwater assessment required Contaminated Sites Framework

 Alberta Tier 1 Soil Guidelines - Dicamba Receptor Human Ecological

Pathway Direct DUA PFAL Livestock Water Irrigation Water Soil contact Soil Type Fine Coarse Fine Coarse Fine Coarse Fine Coarse

Natural 0.5 0.79 BDL BDL

Ag 280 0.5 0.79 BDL BDL 0.12 0.12 BDL BDL

Res/Park 280 0.5 0.79 BDL BDL

Comm 420 0.5 0.79 BDL BDL

Indust 2000 0.5 0.79 BDL BDL

BDL = guideline below detection limit for PFAL or irrigation water  groundwater assessment required Contaminated Sites Framework

 Alberta Tier 1 Soil Guidelines - Tebuthiuron

Receptor Human Ecological

Pathway Direct DUA Direct Soil Contact PFAL Livestock Water Irrigation Water Soil contact Soil Type Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse

Natural 2.5 3.7 0.046 0.046 BDL BDL

Ag 1600 2.5 3.7 0.046 0.046 BDL BDL 0.12 0.11 BDL BDL

Res/Park 1600 2.5 3.7 0.046 0.046 BDL BDL

Comm 2400 2.5 3.7 0.6 0.6 BDL BDL

Indust 11000 2.5 3.7 0.6 0.6 BDL BDL

BDL = guideline below detection limit for PFAL or irrigation water  groundwater assessment required Contaminated Sites Framework

 Receptor Evaluation for Bromacil – Tier 2 Approach Contaminated Sites Framework

 Receptor Evaluation for Dicamba – Tier 2 Approach Contaminated Sites Framework

 Receptor Evaluation for Tebuthiuron – Tier 2 Approach Contaminated Sites Framework

 Other Approaches  Guideline modifications – Influence of Tier 2 Adjustable and Measureable Parameters on Soil Objectives Tier 2 Exposure Soil Soil Bulk Organic K and Source Distance Moisture Density Carbon Hydraulic Length to Objective Pathway or Content Fraction Gradient Type Receptor receptor

Soil Potable Water

Livestock Watering Aquatic Life

Groundwater Potable Water

Livestock Watering Aquatic Life

Page 114 of the Tier 2 guidelines (Table B.1). Caution some of these parameters have caveats associated with them. Contaminated Sites Framework

 Other Approaches - continued  Tier 2 Site-specific risk assessment (SSRA) – typically used to determine ecological or human direct soil contact values. Bromacil and tebuthiuron already have a value however some herbicides do not. Modelling can also be used to develop site specific criteria.  Risk Management – Exposure Control  Engineered controls – introducing carbon to sterilant impacted soils to reduce mobility and aid in degradation of sterilants  Administrative controls – agreement with landowner to not create a dugout or water well near sterilant impacted groundwater/soil. Contaminated Sites Framework

 Other Approaches – continued  Risk Management – continued  Determining Receptors and pathways during risk management Remediation

 Technologies available  Mechanical excavation (default)  Bioremediation (needs more research)  Phytoremediation (needs more research)  Low-temperature thermal desorption (can be expensive)  Incineration (appropriate infrastructure required…can be expensive)  Groundwater recovery and treatment (potential but lithology needs to cooperate) Case Study

 Former Compressor Station  Site located in East Central Alberta  Groundwater Bromacil and Dicamba contamination  Residual groundwater PHC contamination Case Study

 In-Situ Chemical Oxidation  Recommended based on past success in treating other organic based sterilants  ~18,500 L of 15% sodium persulphate solution injected across the Site Case Study

 In-Situ Chemical Oxidation  +ORP was measured in all MW’s across the site (oxidizing state)  Successful remediation of residual groundwater PHC contamination  Minimal decrease in Dicamba concentrations  Statistical modelling (Mann-Kendall) =‘no trend’ Bromacil concentrations Case Study

 Groundwater Recovery and Treatment System  Pilot Study = Granular Activated Carbon (GAC) was most successful in removing Bromacil and Dicamba to below laboratory MDLs Case Study

 Groundwater Recovery and Treatment System  Single recovery well (25.4 cm-diameter) installed on the Site in the centre of the groundwater plume Case Study

 Groundwater Recovery and Treatment System  Evaluated aquifer properties incl. transmissivity, storativity, hydraulic conductivity (pumping test)  Transmissivity = 2.31 x 10-4 m3/s  Storativity = 4.74 x 10-3  K = 2.48 x 10-5 m/s

Recommended pumping rate 8.33 m3/day for 150 days = Removal of 1,250 m3/year*

*maximum GW extraction per AEP Guide to Groundwater Authorization Case Study

 Remediation Options and Treatment for Tebuthiuron at an Upstream Oil and Gas Site  EBA Engineering Consultants Ltd. (RemTech 2009) (http://www.esaa.org/wp-content/uploads/2015/06/09-Lin.pdf) References Acher A.J. and Saltzman S. 1980. Dye-Sensitized Photooxidation of Bromacil in Water. Johnsen, T.N., Jr and H.L. Morton. 1989. Tebuthiuron persistence and distribution in some Journal of Environmental Quality. 9: 190-194; semiarid soils. J. Environ. Quality. 18:433-438;

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