Incremental Sampling Methodology
Fact Sheet for ISM and EPA Method 8330x
Incremental Sampling Methodology (ISM) is a technique designed to statistically reduce or limit variability
associated with discrete sampling. It provides a more representative and reproducible estimate of the mean
concentration of analytes in a specific area of interest, called a "decision unit."
Incremental sampling methodology, also referred to as increment sampling (IS) or multi-incremental sampling (MIS), generally consists of two primary sampling activities: field sampling and laboratory subsampling.
A 1–2 kg sample is collected and sent to the laboratory for
processing in its entirety. It’s composed of 30 to 100 increments of uniform
size collected across a grid formation representing the entire decision unit.
Determining the appropriate size of the decision unit is a critical aspect of
ISM and one that is usually detailed in an approved sampling plan.
Laboratory procedures may vary depending on the contaminants of concern. In general, a subsample is prepared by air drying and sieving the sample through a #10 (2 mm) screen to remove the coarse material. Particle size is reduced by milling or grinding. Finally the sample is spread evenly on a steel tray to a depth of 1/2 inch and divided into 30-50 sections. A one gram aliquot is taken from each section and combined into one sample. The entire sample is then used for sample extraction and analysis.
Current Protocols for Incremental Sampling Methodology
Few official protocols existed in December 2010 and more are expected, including a guidance document from ITRC in 2011.
- Alaska Dept. of Environmental Conservation, Division of Spill Prevention and Response, Contaminated Sites Program, Draft Guidance on Multi Increment Soil Sampling, March 2009.
Refer to http://www.dec.state.ak.us/spar/csp/guidance/multi_increment.pdf for a complete text of the document.
- State of Hawaii Department of Health, Office of Hazard Evaluation and Emergency Response, Technical Guidance Manual for the Implementation of the Hawaii State Contingency Plan, Interim Final – November 12, 2009.
Refer to http://www.hawaiidoh.org/tgm.aspx for a complete test of the document.
- EPA Method 8330B objectives are to highlight those steps that represent a change from historical sampling and analytical methodologies, to provide recommendations as to the appropriate use of the concepts presented in Method 8330B, and to provide recommended minimum method QC requirements for laboratories performing Method 8330B. (Source: Guide for Implementing EPA SW-846 Method 8330B)
Learn more about Reducing Errors Through Incremental Sampling...
Learn more about Incremental Sampling...