In the course of normal construction events, a strange or unusual subsurface condition is often encountered. This condition is characterized by colored liquids oozing from the soil pores along the walls of an excavation, by the emanation of a strong odor, usually associated with petroleum byproducts, or by the uncovering of drums marked "Hazardous Waste," "isobutyl awful stuff," or with similar language. It also happens in the course of normal construction events that a spill, or "release," of hazardous material occurs, such as a fuel or paint thinner spill. In all these cases, the contractor is faced with an immediate problem: what to do.
The correct immediate response is to stop work, shut off valves and plug holes, if possible, and remove personnel from the area as quickly as possible. Then secure the area from inadvertent entry by unauthorized or inexperienced persons, and consider the appropriate response before taking any action. Stopping work costs money, which makes the problem worse, although inappropriate response actions almost always cost even more.
Note that not all contamination discovered on a construction site is historical. Some, unfortunately, is created by the activities of a contractor. Nevertheless, it still must be dealt with and will still cost a certain amount to clean up. The contractor is well advised, therefore, to exercise caution when purchasing construction materials, particularly liquids and powders, to ensure that the safest possible materials are taken onto the site.
Hazardous wastes are a product of hazardous materials. Hazardous spills come from the improper handling of hazardous material and hazardous wastes. The improper handling and use of hazardous materials and hazardous wastes on the construction site are significant causes of contamination problems that must be dealt with by the contractor.
Environmental site assessments are used to determine the presence and extent of surface and subsurface contamination from hazardous materials. This includes assessing the risks to human health, safety and welfare, as well as to the environment, from any contaminants found on the site.
The techniques used to conduct an assessment depend, generally, on the purposes to which the results will be put. For example, an assessment to assist a bank with determining the likelihood of contamination on a virgin forest tract would use significantly different evaluation techniques from an assessment to determine the extent and magnitude of a release discovered through excavation on a construction site. This article focuses on the latter techniques, in conjunction with a generic approach to site assessment. This approach can be adjusted easily as site conditions change from project to project.
In general, surface contamination is determined by a visual inspection of the premises and the testing of surface soils and surface water. In the case of an ongoing construction project, that technique may also work, at least initially, for subsurface contamination. More commonly, subsurface contamination is proved through testing of subsurface soils and groundwater. Subsurface exploration techniques are required to determine the magnitude and extent of any contamination once it has been found. Assessment of the risks to human health, safety and welfare, and to the environment, is usually made by a specialist commonly, a certified industrial hygienist, or CIH.
Once contamination has been identified, it is necessary to develop appropriate cleanup or risk mitigation strategies, collectively called remediation strategies, and to implement those strategies approved by the controlling regulatory agency. Proper use of personal protective equipment and appropriate decontamination techniques will be required during the cleanup or mitigation phase. The reader is cautioned to note the difference between cleanup activities and risk mitigation activities. A mitigation activity removes or limits the risk from the contaminants, but does not remove the contaminants. An example would be the covering of an oil spill site with an impervious concrete cover, to prevent surface water infiltration and contaminant transport, rather than removing the contaminated soil. A cleanup activity removes the source of the risk. In the example above, that would mean completely removing the contaminated soil from the site and replacing it with clean material.
Owners, banks, insurance companies, and developers can do a very preliminary check of known hazardous waste or spill sites through the EPA, or available databases.