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Characterization of Superfund sites
A superfund site is characterized according to its contamination (location, identification, concentration, etc.) and according to its site characteristics: geography, geology/soil types, climate, groundwater (gw) table, gw flow, etc. Each site is unique. Remediation technologies that apply to one site may not work in another site, although the contamination may be similar.
Hydrogeology
The hydrogeology of a site is an indispensable piece of information. A major public health goal is to protect the gw quality. Safe ground water means safe drinking water for a large percentage of the population. If contamination of a drinking water aquifer has occurred, is suspected or is likely, immediate steps must be taken (for example: close gw wells and provide other drinking water sources for the population).
At the contaminated site we have to find out the prevailing soil type(s) and the depth of the water table, the direction and velocity of the gw. Together with the characterization of the contamination we can then make a prediction on the environmental fate of the contaminants. They may be absorbed on soil with a high content of humic acids, they may be blocked due to a thick layer of clay or the water soluble pollutants will be carried off site with the gw.
Review your knowledge on groundwater! Use EPA's "Groundwater Primer" to familiarize yourself with the problem. You can either download the whole primer or view it online. From the main site go to the Table of Contents and select the section on Hydrogeology. In this section please read the following parts:
What is a ground water aquifer?
Water movements in an aquifer.
Please review the information on "Human Modification of
Groundwater Systems": http://www.mhhe.com/earthsci/geology/
mcconnell/demo/gwhuman.htm
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A liquid, water soluble contaminant, that is not easily absorbed on soil, is dumped on the ground. What will happen? |
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A liquid contaminant that is not water soluble and is not easily absorbed on soil, is dumped on the ground. What will happen? |
Example of an uncontrolled contaminated site
Here is an example from Germany, the Brandenburg region, ca. 30 miles
south-west of Berlin. Germany, by the way, has over 360,000 sites with suspected or confirmed contamination. Follow this link for a list of contaminated sites in Germany:
http://www.umweltbundesamt.de/altlast/web1/
englisch/1_6.htm
The lakes shown here are the remainders of open pit mining
in former East Germany. The water is very acidic with high heavy metal
contents. This is an example for a "co-disposal landfill". You can
see drums (half buried, maybe corroded) and solid and liquid wastes that
mix freely. There is residential housing in the background. Children sneak
through the holes in the fence and play near the lakes. In a situation
like this we are concerned with a number of contamination problems:
- Multimedia contamination: surface water, groundwater, soil, air, biota
- Mobility/migration of contamination: groundwater movement and surface water floods carry water-soluble contaminants off site, may be endangering drinking water sources; airborne contamination (dusts and volatile materials) may drift off site
- bio-accumulation of toxic substances in the food chain: plants, fish/shellfish, birds, land animals.
- Mixed pollutants, their breakdown products and products of chemical reactions
Other important consequences of CERCLA:
ATSDR: CERCLA also established the Agency for Toxic Substances and Disease Registry - ATSDR. In the next section we will look closer at ATSDR's role: to advise EPA regarding health effects of hazardous waste and toxic substances, among other things.
NCP: the National Contingency Plan (NCP) covers emergency response to hazardous waste spills, oil spills and releases from HWS that require emergency removal actions. We will look into that matter in the third section.
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