Environmental geology outline - groundwater quality and contamination

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:

Groundwater contamination sources:

Contaminant plume geometry and clean up:

Above is a simple schematic of point source, its associated contaminant plume and contours on the water table of a simple unconfined aquifer. This is a basic approach geohydrologists often use in some form. What direction is the groundwater flowing? Given the scale, and a ten year time span since the point source was created, at about what speed are the contaminants moving? How long before they might reach the surface drainage (stream)? Note that contours on the plume are sub-perpendicular to those of the ground water table.

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:

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.

Some clean-up case histories

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

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