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Groundwater Sampling

Examining the types of contaminants in groundwater, how to monitor contaminants, and the tools used in sampling +cases
by

Laurel Hoffarth

on 16 February 2012

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Transcript of Groundwater Sampling

Groundwater Contaminant Transport Fate of NAPLs
Transpotation vs Transformation

Transportation
- Solution is Dilution
- Reduction in concentrations
- Bioaccumulation still occurs

Transformations
- Biodegradation
- Decay Rates (zeroth/first order)
- Byproducts are not always less toxic Types of Contaminants Sampling Tools Sampling Techniques PCBs in Smithville Groundwater
Contaminant
Transport Site History and Contaminant Origin Site Investigation Anyone really good at mazes? PCB Plume TCE Plume DNAPLs LNAPLs Aqueous
Phase Pathogens PPCPs Quarry Exposed Bedrock Boreholes and Wells Geologic Sequence Fractures and Karst Geology Cross Section Hydrometric Measurement and Sampling Atmosphereic gas and contaminant sampling Surface water
stream measurement Surface water
quality measurement QA/QC Analytical Methods Infiltration and overland run off Spacial analysis and statistics Soil classification
(test pit, borehole logs) Aquifer testing Regulations & Guidelines Ontario Regulation 903

U.S. Environmental Protection Agency Guidelines Lock and tag wells

Purge a minimum of three casing volumes
Measure field parameters
Sample for selected parameters
Field preservation
Transportation Borden Site Sampling for Specific Contaminants Measure Field Parameters Sample Collection Well Construction Drive-point Piezometer Well Tubing Peristaltic pump Waterra Footvalve Grab Sampler Multiparameter Meters Flow-Through Cell Field Preservation Sampled Parameters Volatile Organic Compounds (VOC’s)
Metals (including hydride-forming metals, calcium, magnesium, sodium)
Mercury, methyl mercury
General chemistry
Hexavalent chromium
Alkalinity
Dissolved Oxygen
Cyanide
Conductivty, chloride, pH
Fraction organic carbon (FOC)
BTEX (Benzene, toluene, ethylbenzene, xylenes)
Petroleum Hydrocarbons (PHCs)
Polychlorinated biphenyls (PCBs)
THM (Trihalomethanes)
1,4-Dioxane
Dioxins and furans
Polycyclic Aromatic Hydrocarbons (PAHs) Lithology Considerations Attenuation
of
Contaminants Physical Biological Chemical Hydrolysis Dehydrohalogenation Aerobic Anaerobic Hypoxic Volitalization Dispersion Sorption DNAPLs sink due to densities greater than water

Less permeable units can prevent downward flow

Pools can form on impermeable units

The aqueous phase will travel with the flow of groundwater DNAPL Flow in a Homogeneous Gravel/Sand Aquifer Fractured Media Case Study:
Woburn Water Contamination TCE
PCE Contaminated
Detected Drinking Water
Standard (2011) 267.4 ug/L
20.8 ug/L 5 ug/L
5 ug/L LNAPLs
light non-aqueous phase liquids
less dense than water
immiscible fluid
examples: benzene, toluene, xylene Partitioning Transport Dissolved Contaminant Plume DNAPLs
dense non-aqueous phase liquids
more dense than water
immiscible fluid
examples: TCEs, PCBs, halogenated hydrocarbons Wettability Aqueous Phase Contaminants

High solubility in water
Can partition into gas phase and/or adsorb to soils
Examples: nitrogen, phosphorus, metals, ionic compounds Transportation

Fick's Law Contaminant Plumes Contaminant Consideratons DNAPLs


LNAPLs


Aqueous


Pathogens & PPCPs Sink until they hit an impermeable barrier
Submersible pump

Sink until they hit the water table
Drive points or shallow wells

Miscible in groundwater
Close off undesired layers using packers

Aqueous phase
Standard sampling procedures Monitored Parameters pH: +-0.2 pH units
Conductivity: +-3% of reading
Dissolved Oxygen: +-10% of reading
Eh or ORP: +- 20 mV
Turbidity: +-10% of prior reading depends on fracture size and aperture

fractures act as conduits for DNAPL to flow through

can reach a depth of greater than a 1000m Remediation
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