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Last modified
7/29/2009 9:47:28 PM
Creation date
10/12/2006 3:38:59 AM
Metadata
Fields
Template:
Water Supply Protection
File Number
8040.500
Description
Section D General Studies-Groundwater
Date
1/1/1984
Author
EPA
Title
EPA-Draft Groundwater Protection Strategy-January 1984-Draft Ground Water Protection Strategy-EPA SR 84-04
Water Supply Pro - Doc Type
Report/Study
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<br />- 10 - <br /> <br />water is more easily accessible than surface water. In scme <br />parts of the country ground water is often the only available <br />source of drinking water and can generally be used with little <br />or no treatment. <br /> <br />Once contaminated, around water oresents oarticularly diffi- <br />cult problems for monitoring and clean-up. In many ways ground <br />water is a far more complex resource than air or surface water. <br />Ground water is slow-moving, with velocities generally in the <br />range of 5 to 50 feet per year. As a result, large amounts of <br />a contaminant can enter an aquifer and r~main undetected until <br />a water well or surface water body is affected. Moreover, con- <br />taminants in ground water--unlike those in surface water--often <br />move in a plume with relatively little mixing or dispersion, so <br />concentrations remain high. These plumes of relatively concen- <br />trated contaminants move slowly through the aquifer and are <br />typically present for years--sometimes for decades or longer-- <br />making the resource virtually non-renewable over short periods <br />of time. There is little opportunity foe chemical or biological <br />transformation, so little degradation of contaminants takes place. <br />Because an individual plume may underlie only a very small part <br />of the land surface, it is difficult to detect by aquifer-wide <br />or regional monitoring. <br /> <br />Beyond this, monitoring is expensive, since multiple test <br />wells must be drilled to define the affected areas once a source <br />of contamination is identified. The slow movement of ground <br />water makes restoration after .contamination complex and expensive. <br />Its success is unpredictable. For example, in the case of a <br />gasoline spill, where the contaminant is valuable, recovery <br />systems are typically 40-60% effective at best. In most circum- <br />stances it is prudent to protect the resource from contamination <br />in the first place, rather than rely on clean-up after the fact. <br /> <br />Ground-water contamination is of particular concern because <br />of ground waters direct use as a drinkinc water source bv 50% <br />of the U.S. oooulation. Approximately 117 million people in <br />the U.S. get their drinking water from ground water supplied by <br />48,000 community public water systems and approximately 12 million <br />individual wells. The remaining population receive their drinking <br />water from 11,000 public water systems drawing from surface water <br />sources. About 95% of rural households depend on ground water, <br />as does a still larger proportion (97 percent) of the 165,000 <br />non-community public water supplies (such as camps, or restaurants <br />serving a transient population). Finally, thirty-four of t~e 100 <br />largest U.S. cities rely either completely or in parton ground <br />water.ll <br />
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