1.2 Traditional Investigation Approach Limitations
Soil sampling is typically done to characterize a site. Historically, the majority of soil samples collected have been discrete samples. Collection of discrete samples is sometimes preferred or mandated by regulatory agencies. Over the years, consultants, environmental scientists, and regulators have become aware of a number of recurring challenges, problems, and deficiencies associated with collecting soil samples as discrete, composite, or any other sampling method, including the following:
- Lack of clear environmental objectives at the initiation of the investigation—Often the primary objective is to “find contamination” with little clarity as to how the data will be used to determine whether identified contamination poses unacceptable risks to human health and the environment and often leading to lengthy delays in completion of project and expenditure of funds available for site investigation before adequate characterization is completed.
- Poor spatial coverage of areas targeted for investigation and inadequate sample density—Generally, a minimum of 20–30 discrete samples is needed for an adequate characterization of a targeted area and volume of soil; however, only a small number (e.g., <10) of discrete samples are commonly collected to characterize large areas of suspected contamination. The degree of coverage is typically controlled by the amount of funds available for laboratory sample analysis, thus limiting the number of samples needed to provide a representative and statistically valid characterization of a targeted area.
- Laboratory aliquots prepared for analysis not necessarily representative of the field sample—Aliquots prepared by random selection of a single, small mass of soil from the field sample container are not representative of the larger volume of soil delivered to the laboratory.
Traditional soil sampling and analysis methods impart a level of uncertainty in the use of data generated to identify potential environmental hazards associated with contaminated soil and to support decisions for or against remediation. In large measure, ISM is evolving to address these limitations.