EOSC 429 · Groundwater Contamination

Principal learning goals

This is a practical applied course that will introduce some specific analysis skills and build a framework for understanding and managing contaminated-groundwater problems.

As owner, consultant, government regulator or NGO if you encounter a site with contaminated groundwater, or plan a site where contamination is possible, you will have learned:

What are the right questions to ask at the site?

What are the important field / lab data that should be collected?

How should the field and lab data be interpreted?

How to predict the fate of the contamination?

How to assess the reliability of your predictions?

The course deals with contaminant transport processes in groundwater flow systems, aqueous and multiphase transport, mathematical models describing migration and chemical evolution of contaminant plumes and presents some case studies.

Detailed learning goals

• Identify the key processes affecting contaminant transport and transformation: articulate the importance of groundwater flow and physicochemical reactions on contaminant transport
• Can translate a real-world situation into a conceptual model and then boundary value problem;
• Properly identify both flow and transport boundary conditions from observations and information collected at a real-world site.
• Use knowledge of groundwater flow to predict advective and dispersive transport – travel times, concentrations and breakthrough curves
• Can use simple mass balance concepts to compute rates of mass change within a volume or region.
• Identify key parameters required to determine flow directions and rates and therefore advective component of transport
• Compute travel times from flow net and / or piezometric patterns
• Qualitatively relate the degree of heterogeneity to the amount of spreading
• Qualitative and quantitatively estimate the role of scale / resolution on flow rates, the relative magnitude of dispersivity and peak concentrations.
• Compute solute fluxes by advection, dispersion and diffusion given flow and concentration data
• Can use simple analytical models of diffusion, advection and advection/dispersion to compute concentrations, solute fluxes, and travel times.
• Distinguish between spreading, dispersion and dilution.
• Recognize the advection-dispersion equation in 1, 2 and 3 dimensions and be able to identify the physical processes represented by each term in the equation.
• Know the advection – dispersion equation in one dimension (commit this one to memory).
• Predict advective and dispersive transport – travel times, concentrations and breakthrough curves
• Determine flow directions and rates: advective component of transport
• Compute travel times from flow nets or piezometric patterns
• Articulate the role of scale/resolution on the relative magnitude of dispersivity
• Compute solute fluxes by advection, dispersion and diffusion given flow and concentration data
• Use simple analytical models of diffusion, advection and advection and dispersion to compute concentrations, solute fluxes, travel times
• Use simple mass balance concepts to compute mass loss rates
• Read a volumetric water content versus suction characteristic curve to determine the change in water content for change in suction and identify soil type.
• Compute groundwater flow under gravity drainage in the unsaturated knowing the infiltration rate and the relationship between hydraulic conductivity and moisture content ( hydraulic conductivity characteristic curve) –from a graph of  of a functional relationship such as the Brooks and Corey model.
• Be able to match a site description and data to common conceptual models of LNAPL and DNAPL contamination.
• Be able to identify the key controls and NAPL movement in both the vadose zone and the saturated zone.
• Compute concentrations of dissolved NAPL in water in equilibrium with either a pure NAPL phase of a NAPL that is a mixture of several compounds using solubility or solubility and Raoult’s law.
• Compute the concentrations of NAPL in the vapor phase in equilibrium with a dissolved plume using Henry’s law.
• Compute the concentration of NAPL in the vapor phase in equilibrium with a pure phase NAPL or a NAPL phase that is a mixture of several compounds using Raoult’s law.
• Identify the wetting and non-wetting phase by observing contact angles and interface curvatures at the pore scale.
• Compute capillary pressures knowing surface tensions, contact angles and pore – throat diameters.
• Be able recognize processes that change capillary pressures and affect the movement of NAPL.
• To recognize and distinguish between the behavior of DNAPLs and LNAPLs in both the vadose and saturated zones – for example how would a gas leak at depth move in the saturated zone?
• Compute maximum DNAPL pool height before threshold entry pressure is attained.
• Understand the process of sorption for both inorganic and organic contaminants and be able to identify or compute K_d and/or K_oc for a given contaminant when given appropriate information
• Understand the process of retardation and be able to compute values for a given contaminant including the effect on velocity in groundwater
• Understand the redox system in the context of groundwater including redox zonation and the plumes fringe concept as well as oxidation capacity and its calculation
• Understand in a general sense potential drilling methods and groundwater monitoring systems (i.e. multi-level monitoring systems) and their installation
• Can design a site investigation and consider the tradeoff between cost and data