# How much ground water have we really polluted?

Screaming headlines about toxic tragedies have all but drowned out the quiet truth that we Americans have yet to pollute 1 percent of our total ground water supply.

It is in the best interest of the public to better understand the situation. Ground water pollution, while serious, is not quite the crisis some have led us to believe. We have a problem, certainly, and we want action. But we do not need any Chicken Littles telling us that the sky is falling, because it most certainly is not.

To make my case, I must be permitted some assumptions. I assure you all of them are conservative.

Assume there are 200,000 sources of pollution oozing into the ground - from septic tanks, landfills, pits, ponds, and lagoons. That is a high number. Most experts put the number of industrial sites at 75,000 to 100,000. I have doubled the figure to include everything, even innocuous sources. Let's further assume that each source is creating a plume of pollution 1,000 feet wide and 100 feet thick. A conservative estimate would be that each plume moves about four inches per day or roughly 125 feet per year, and has been traveling for approximately 40 years (a longer history than most). Forty years at 125 feet per year is 5,000 feet - about a mile. So each of these 200,000 plumes has moved a mile from its source.

Let's assume that the plumes are contaminating aquifers that are 25 percent porous, a realistic figure. Now, how much water have we polluted? Multiply 200, 000 by 1,000 feet (width) by 100 feet (thickness) by 5,000 feet (length) and divide it by .25 (porosity), and you get 25 trillion cubic feet, which converts into 200 trillion gallons of polluted water - a slight 2/10 of 1 percent of the 100 quadrillion gallons of available ground water!

Even if you insist that the average plume is 1,500 feet wide, we only have polluted 3/10 percent. If you also want to say that the plume is 150 feet thick, then we have polluted .45 percent. If you believe the average plume has gone 1.5 miles instead of 1.0 miles, then we have polluted .675 percent. If you are convinced that there are 300,000 plumes, then perhaps the figure reaches 2 percent. But no matter how liberally or conservatively we slice it, we are dealing with a very small fraction of our water supply.

One argument that mightm weaken my thesis is that we have polluted the water unevenly, and concentrated our misdeeds where our dependence on it is greatest. In the industrial sections of New York, New Jersey, and New England, we have indeed polluted a lot more than 1 percent. This is a serious problem, but there still is a considerable amount of unpolluted water available in these areas as well. In addition, we will likely uncover many more yet unknown locations of severe ground water pollution. But one should not be led to the conclusion that such sites are everywhere, for they are not.

I believe we can eliminate new sources of pollution and put an end to ill-conceived toxic dumps within 10 years. The existing plumes will not have moved much further or polluted much more in that time. The odds are in our favor to end up with 98 percent of our ground water still unpolluted at the end of this century.

However, we must start work now. We must take strong measures to protect our water supply from further pollution and strive to keep existing contamination at bay. Using new pollution cleanup technology, we will be able to restore some aquifers. It may well be costly to do so, but whatever the debt, it is a small price for safe drinking water.

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