The top of this zone is called the water table. The water table may be only a foot below the ground's surface or it may be hundreds of feet down. Groundwater can be found almost everywhere. The water table may be deep or shallow; and may rise or fall depending on many factors. Heavy rains or melting snow may cause the water table to rise, or an extended period of dry weather may cause the water table to fall. Groundwater is also one of our most important sources of irrigation water. Unfortunately, groundwater is susceptible to pollutants. Groundwater is generally a safe source of drinking water; however, there are concerns that contamination may increase as toxins dumped on the ground in the past make their way into groundwater supplies. Pollutants that contaminate groundwater may be some of the same pollutants that contaminate surface water. Compounds from the surface can move through the soil and end up in the groundwater. For example, pesticides and fertilizers can find their way into groundwater supplies over time. Road salt, toxic substances from mining sites, and used motor oil also may seep into groundwater. In addition, it is possible for untreated waste from septic tanks and toxic chemicals from underground storage tanks to contaminate groundwater. Drinking contaminated groundwater can have serious health effects. Contaminated site poses considerable risk to human health and the environment also contaminated soil functions are endangered because of impacting contaminant levels (Spalton 2008). Diseases such as hepatitis and dysentery may be caused by contamination from septic tank waste. Poisoning may be caused by toxins that have leached into well water supplies. And it is important not to forget that wildlife, too, can be harmed by contaminated groundwater. Deterioration of soil quality, loss of soil functions and water resources degradation should be avoided as prevention and remediation is to restore land use and soil functions (or natural background levels) (Spalton 2008). Laboratory, soil and water, rock, chemical (for effect on construction materials), contamination (Analytical - pH, organics, inorganics, metals, asbestos) tests are applied in order to define the current pollution situation of the specified site and for applying the proper remediation methodology (Spalton 2008).
Contaminated Land Exposure Assessment (CLEA) Model
Contaminated Land Exposure Assessment (CLEA) Model describes the conceptual exposure models for each standard land-use. CLEA model is shown in Figure 1.
Figure 1. Illustration of potential exposure pathways in CLEA model (Spalton 2008)
Remediation of Soil and Contaminated Groundwater
Remediation, in this sense, is a broad term that refers to the reduction of risk caused by exposure to contaminated groundwater. Although there were various reasons for the failure of the systems to meet their goals, the data strongly suggest that, for most circumstances, best available technologies are not capable of restoring groundwater to its original quality. However,