Chapter 8: Groundwater Flashcards
What are the four parts to Groundwater?
- Unsaturated Zone: air, water, soil. Water is held in tension and considered unavailable.
- Capillary Fringe: up to 100% saturated, but water held in tension.
- Water Table: upper bound of Saturated Zone
- Saturated Zone: Water and soil - water flows as groundwater.
What is an aquifer?
A saturated layer permeable enough to allow water flow. Water can be pumped economically.
What is an aquitard?
Saturated layer not permeable enough for easy water flow. Water can’t be pumped out economically.
What is Groundwater?
Water contained in interconnected pores below water table in an aquifer.
What is Groundwater Flow?
The movement of water through openings in sediment and rock.
What does Artesian mean?
A confined aquifer with water that flows upward out of a well.
What does Perched mean?
Groundwater above a permeable layer - usually above aquifer.
What is the hydraulic gradient?
The slope of water table to difference in hydraulic head b/w 2 points (i)
What is Porosity?
ratio of volume of voids to total volume
What is Effective Porosity?
ratio of interconnected pore spaces to bulk volume
What is hydraulic head?
surface elevation minus distance to water table
What is pressure head?
Depth of well from surface minus distance to water table from surface
What is elevation head?
surface elevation minus depth of well
What is the difference between Darcy Flux and groundwater velocity?
Darcy velocity assumes no soil in cross section (open pipe flow), whereas groundwater velocity takes into account the porosity (ie. soil in the way)
What are the three methods of contaminant transportation?
- Advection: due to groundwater flow
- Dispersion: due to irregular flow paths
- Diffusion: due to concentration gradient
What is Plume?
Dissolved contaminants
What are some attributes of dispersion?
- micro, macro, and mega scales
- smaller pores = higher velocity
- higher velocities = higher dispersion
What are some attributes of diffusion?
- Contaminant plume moves from high concentration to low
- Important in low velocity soils (clay/bedrock)
What is Adsorption?
The property of a solute to attach to a surface of a solid
What is Absorption?
The property of a solute to attach to surface of a solid, then penetrate the solid
What is Retardation?
When contaminant velocity is slower than groundwater velocity.
What are NAPLs?
Non-Aqueous Phase Liquids
What are LNAPLs and DNAPLs?
Less dense than water - LNAPL
More dense than water - DNAPL
What are some attributes of NAPLs?
- Ganglion form as NAPL migrates
- Immobile
- Long term source of groundwater contamination
- Difficult to remove or remediate
What are the steps in Contaminated Site Management?
- Site Investigation
- Remediation Plan & Implementations
- Confirmation of Remediation - certification
- Long-term Monitoring
What are some remediation technologies for groundwater?
- Fluid pumping
- Mass destruction
- Enhanced fluid pumping
- Enhanced bioremediation
What does Groundwater Pumping involve?
- Uses advective treatment methods to remediate
- Contaminant and fluid brought to surface for treatment
- Hydrodynamic/hydraulic control
What is SVE?
Air Flushing:
- Soil Vapour Extraction
- Unsaturated Zone: Soil remediation
What is Air Sparging?
Air Flushing:
- Saturated Zone: Plume remediation
What are PRB’s?
Permeable Reactive Barriers.
They passively intercept contaminants passing through the barrier where they react and are broken down by a reactive material.
What is ISCO?
In-situ chemical oxidation.
Oxidation converts hazardous contaminants to non-hazardous compounds that are more stable.
What are common oxidizing agents used?
- Ozone
- Hydrogen Peroxide
- Permanganate
What are some benefits of ISCO?
- applicable to a variety of soil types
- Can treat VOC’s and SemiVOC’s
- Rapid destruction
- No significant waste
What is MNA?
Monitored Natural Attenuation
Naturally Occurring processes that act without human intervention to reduce contaminants in soil/groundwater.
What are Reactive Zones?
Zones created by injection of air/oxygen that treats contaminants through biodegredation.
What is Thermal Remediation?
Use of heat to destroy contaminants.
- Conduction heating
- Steam injection
What is Phytoremediation?
Use of plants to address contamination issues.
