ASTM D6982-03

Search sampling strategies have found wide utility in geologic exploration where drilling is required to detect subsurface mineral deposit, such as when drilling for oil. Using such strategies to search for buried wastes, subsurface contaminants, and underground structures is a logical extension of these strategies.

Systematic sampling strategies are often the most cost-effective method for searching for hot spots or buried objects.

Search sampling patterns may also be used to optimize the locations of ground water monitoring wells or to optimize the location of vadose zone monitoring devices.

This practice may be used to determine the risk of missing a target of specified size and shape given a specified sampling pattern and sampling density.

This practice may be used to determine the smallest target that can be detected with a specified probability and given sampling density.

This practice may be used to select the optimum grid sampling strategy (that is, sampling pattern and density) for a specified risk of not detecting a hot spot or buried object.

By using the algorithms given in this practice, one can balance the cost of sampling versus the risk of missing a hot spot or buried object.

1.1 This practice provides equations and nomographs, and a reference to a computer program, for calculating probabilities of detecting hot spots (that is, localized areas of soil or groundwater contamination) and buried objects using point-net (that is, grid) search patterns. Hot spots, more generally referred to as targets, are presumed to be invisible on the ground surface. Buried objects may include former surface impoundments, waste disposal pits, and utilities that have been covered by soil or paving materials. Hot spots may also include contaminant plumes in ground water or soil gas.

1.2 For purposes of calculating detection probabilities, hot spots or buried objects are presumed to be elliptically shaped when projected vertically to the ground surface, and search patterns are square, rectangular, or rhombic. Assumptions about the size and shape of suspected hot spots are the primary limitations of this practice, and must be judged by historical information. A further limitation is that hot spot boundaries are assumed to be clear and distinct. Alternative approaches to hot spot detection using discrete sampling should also be considered where feasible, such as surface geophysical measurements (see Guide D 6429).

1.3 Search sampling would normally be conducted during preliminary investigations of hazardous waste sites or hazardous waste management facilities (see Guide D 5730). Sampling may be conducted via drilling or by direct-push methods. In contrast, guidance on sampling for the purpose of making statistical inferences about population characteristics (for example, contaminant concentrations) can be found in Guide D 6311.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.