Groundwater Contamination (1984) / Chapter Skim
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Overview and Recommendations
Overview and Recommendations
Pages 3-20
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From page 3... ...
Because of the volumes of toxic wastes and because of their stability in groundwater, such contamination can pose a serious threat to public health. Grounc~water is the subsurface transporting agent for dissolved chemicals including contaminants.
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This may involve TABLE 1 Preliminary Findings of the EPA Surface Impoundment Assessmenta 10,819 19, Il6 14,677 7,100 24,527 1,500 77,739 25,749 36,179 19,167 24,451 64,951 5,745 176,242 Category Industrial Municipal Agricultural Mining Oil/gas brine pits Other Sites Located Impoundments Located Sites Assessed 8,193 10,675 6,597 1,448 3,304 327 30,544 The Surface Impoundment Assessment also released analysis based on data from the assessed industrial sites. · Almost 70 percent of the industrial impoundments are unlined.
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From page 5... ...
However, certain nondegradable nanny toxic substances along warn some of the radioactive wastes with very long-lived radionuclides may require permanent isolation. If the subsurface is to be utilized as a repository of wastes, both increased scientific knowledge and improved engineering techniques must be brought to bear on the problem of groundwater contamination.
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From page 6... ...
GROUNDWATER: THE RESOURCE Groundwater is a heavily used resource; its magnitude has been described in the U.S. Water Resources Council Bulletin 16 (1980~: The Nation's groundwater resource is enormous it is our largest freshwater source in terms of volume in storage.
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From page 7... ...
The situation on Long Island, New York, illustrates the impact of widely distributed small point sources of pollution on an aquifer system where approximately 3 million residents rely on wells as their sole source of water supply. Domestic wastewater seeping from thousands of septic systems and leachates from landfills and industrial waste-disposal sites have contaminated the shallow groundwater in many parts of Long Island, as described in Chapter 9.
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By combining injection and production wells in a manner similar to their use in oil reservoirs, groundwater flow through the ore body is controlled. Chemical reagents are usually introduced that make the mineral of interest more soluble and thereby more economically recoverable by the moving fluids.
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Deep Injection or Burial Deep burial of toxic wastes has several advantages over shallow burial or surface-storage systems. The most important advantage is that contaminants that may become dissolved in groundwater will not migrate directly to the land surface.
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At Oak Ridge National Laboratory, in a use of the concept of multiple barriers, radioactive wastes have been mixed with cement and implaced by hydraulic fracturing techniques in low-permeability shale. In the arid and semiarid portions of the western United States, thick unsaturated zones often overlie a deep water table.
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From page 11... ...
as a strategy of "out of sight, out of mind." A number of disposal sites have proven to be effective in containment and reasonably safe. In some instances, careful thought and planning in site selection and disposal practices have led to safe containment of highly toxic wastes.
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With conservative contaminant transport (transport without chemical reactions) a physical mixing occurs that is generally referred to as hydrodynamic dispersion.
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The chemical processes involved with organic contaminant transport are reviewed in detail in Chapter 3. As examples, Chapter 6, dealing with problems at the Rocky Mountain Arsenal, and Chapter 10, dealing with a landfill in Delaware, highlight some of the problems with organic contaminants.
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From page 14... ...
(Some toxic organics may not be totally broken down to nontoxic components using current incineration practices.) It may well be that the toxic organic compounds that cannot be incinerated or treated to make them less hazardous on a practical basis will have to be disposed of by deep burial, a methocl now proposed for radioactive wastes.
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The Idaho National Engineering Laboratory (INEL) is a wellstudiecl example where there are three major classes of contaminant transport: conservative (i.e., chloride)
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j l\ m? , ~ EXPLANATION EQUAL CHLORIDE CONCENTRATION IN mg/ ~ FOR 1968-69 50 WELL SAMPLES ~ 50 DIGITAL MODEL FIGURE 2 Comparison of waste chloride plumes in the Snake River Plain aquifer (at INEL)
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From page 17... ...
Nevertheless, in response to public or governmental demands for positive action in cases where groundwater contamination threatens public health, aquifer cleanup programs are being required, such as at the Rocky Mountain Arsenal and more recently in "Silicon Valley" near San lose in California where organic solvents have been found in the groundwater. General management options currently available for restoring water quality in aquifers include the following: (1)
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From page 18... ...
be a more thorough searchfor disposal sites that can be used safely to isolate toxic wastes from the biospherefor long periods. If a policy is adopted to establish disposal sites in the vicinity of the facility generating the wastes, sites must be located that provide the necessary multiple barriers to contaminant migration.
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From page 19... ...
III. Particularly toxic wastes that are not readily treatable, such as some of the highlevel radioactive wastes, or are persistent and mobile in groundwater.
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From page 20... ...
. Radioactive and chemical waste transport in groundwater at the National Reactor Testing Station, Idaho: 20-year case history, in Proceedings of the International Symposium on Underground Waste Management and Artificial Recharge, Am.
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