What might people want to know about the water they drink and use (water quality measures)?

Science of aqueous geochemistry a critical one here.

Aquifer contribution to groundwater chemistry:

• 3 important factors: rock type, time, water chemistry (e.g. pH).
• limestone and hard water.
  • pH typically 7-8.2
  • if > 80 -100 ppm then hard.
  • can also be high in SO2
  • water softeners typically used: exchange Na for Ca, Mg ions.
• granites:
  • pH 6.3-7.9.
  • Na and K predominant ions, Fe common also.
• sandstones: generally low TDS, high quality.
• time factor: the older the higher the TDS, old formation waters essentially brines.

Groundwater contamination sources:

• point sources vs. non-point sources.
• What are examples of point sources in urban environment (the urban landscape from an environmental perspective)?
• some statistics.

Contaminant plume geometry and clean up:

• maps of groundwater surface and contaminant plume - how compiled?
• observation well samples and contours of contaminant concentration.
• reaction fronts, sinkers and floaters, and a 3-D approach.
• What are some clean up methods?
• cost-benefit analysis and clean-up standards.

The above is a schematic graph showing the relationships between cost and the level of clean-up. It is a very useful initial framework for considering the question of what level of clean-up should be undertaken for a given contaminated site. Perhaps consider two different perspectives: that of someone living next to the site, and that of the administrator with a fixed budget who has the responsibility of cleaning up many more sites than he has money for. Most important to note that it may be several times the cost to clean up the last 5% or so of contaminant. More recently, faced with large costs and limited resources, clean-up fund administrators are taking a cost-benefit approach. The basic trade off is between cleaning up a few sites to pristine levels versus cleaning a larger number of sites to lower levels.

Practice exercise.

Common contaminants:

• major groups of contaminants: pathogenic organisms, inorganic compounds, organic compounds, radioactive nuclides?
• common organic compounds (solvents, lubricants, pesticides)
  • stability and residence time?
  • hydrocarbons: gasoline one of the most common.
  • chlorinated organics: powerful solvents and cleaners:
    • PCE: perchloroethylene (used in drying cleaning).
    • TCE: trichloroethylene (common grease cutter).
    • DCE: dichloroethylene
    • all carcinogenic.
  • floaters and sinkers (DNAPLs - dense non-aqueous phases).
  • vinyl chloride: used in plastic production, angiosarcoma, mostly a concern to workers.
  • up to 1000 new industrial chemicals invented each year.
• radioactive material/nuclides of concern?
  • biomagnification
  • strontium-90, cesium-137, iodine-131, radon-222, plutonium-239
  • will cover more in context of nuclear power.

Legal and regulatory framework. This framework is extensive and complex, to the point that some people make a living just at helping industry stay in compliance. Below are just a few of the highlights, major pieces of legislation.

• Water Pollution Control Acts (1956,65,72)
• National Environmental Policy Act (1969): requires EIS, environmental impact statements
• Comprehensive Environmental Response, Compensation and Liability Act (1980): also known as Superfund, National Priority List
• Resource Conservation and Recovery Act (1988): for better record keeping, permitting and database formation.
• Environmental Protection Agency
• Nebraska Department of Environmental Quality. This is our lead agency for environmental issues in Nebraska. Each state has an equivalent agency.

Some clean-up case histories

• Love Canal, western New York.
• Rocky Mountain Arsenal, N of Denver, Colorado.
• Are there any superfund sites in Nebraska?
• forensic environmental geology.

We will return to some of these considerations when we talk about waste disposal and landfill design in the next part of the course.