Overview. Planning. DU Types

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1 Incremental Sampling Methodology Harry Behzadi, Ph.D., Accutest Laboratories, Orlando FL Bruce Nocita, Ph.D., P.G., S&ME Inc., Tampa, FL Incremental sampling methodology (ISM) is a structured composite sampling and processing protocol that reduces data variability and provides a reasonably unbiased estimate of mean contaminant concentrations in a volume of soil targeted for sampling. Overview The distribution of contaminants in soil is currently established from discrete samples collected using professional judgment and usually from sampling locations that have some sort of bias i.e. a sampling plan. These plans differ in many ways due to site history, nature of contaminants, source of contamination etc. However, all sampling plans using discrete samples have two things in common; biased sampling strategy and low sampling density for the overall site. By its very nature, soil is a highly heterogeneous solid with many components. Sampling soil for the purpose of obtaining an estimate of the mean contaminant concentration is highly susceptible to sampling errors from a variety of sources. Traditional discrete soil sampling methods don t always provide the accurate, reproducible, and defensible data needed for effective project planning. A well designed incremental sampling plan can yield a single sample for analysis that has physically captured the population diversity such that it represents the mean of the target population in a specified volume of soil for which a decision needs to be made. This volume is termed a Decision Unit (DU). Systematic planning must be done before developing a sampling design. Planning Sampling design must include 1) a conceptual site model; 2) a clear understanding of the objectives; and, 3) data needs and sampling approach (e.g. spatial scales). Decision units may be defined in regularly spaced and equal volumes; may be based on irregular features of the site which define contaminant transport or receptor exposure; may be based on an understanding of the contaminant distributions, e.g. in and around source areas; and, need to consider remedial design. ISM samples are designed to contain all constituents in exactly the same proportion as the area designated as a DU. The mean concentration in the DU is the basis for the decision. DU Types Release/Source Area DUs (e.g., drums, waste pits, soil around primary sources, etc.). These focus on investigation of obvious or suspected contaminated areas and identify contaminants of potential concern. These DUs can flag potential environmental problems that warrant additional attention 1

2 Exposure Area DUs (e.g., exposed soil in yard). These focus on risk to humans (or ecological health) and are used in traditional human health risk assessments. Subsurface Decision Unit 2

3 Field Sampling Field sample collection: Collect multiple (> 30 to 100) increments of uniform mass from the entire area to be represented (DU).Composite the increments into a single sample (1-2 kg) to address compositional and distributional heterogeneity. Sampling tools should obtain cylindrical or core-shaped increments of a constant depth Laboratory Processing & Sub-sampling A lot of effort is typically spent improving analytical reproducibility and validating analytical results, even though it is the smallest source of error in environmental data. ISM involves two components: field sampling and laboratory sub-sampling. Laboratory procedures may vary depending on the contaminants of concern. In the laboratory, the ISM (for non-volatile analyses) is typically air dried and sieved to<2mm. Further processing depends on the method or type of contaminant to be analyzed; for instant samples for metals analysis are ground by mortar and pestle while samples for explosive analysis are ground by Ring and Puck mill. In the lab, subsampling is accomplished by the Gy sampling theory, which is the foundation of the multi increment sampling approach. A representative sub-sample is hand collected by taking 30 small increments from random locations from the dried, sieved, and ground sample which has been spread out to a thin layer. Sub-sampling is used to provide a representative laboratory subsample for a single multi-increment sample, and to provide representative sub-samples for multiple analyses. 3

4 As far as analysis explosive by method 8330A, The U.S. Army Corp of Engineers Cold Regions Research and Engineering Laboratory (CRREL) demonstrated that traditional field sampling and laboratory sub-sampling methodologies are not able to accurately represent conditions at the site. As a result, the paper on surface soil sampling at DOD firing ranges and relevant methodologies was published in 2007 by CRREL in a document titled Protocols for Collection of Surface Soil Samples at Military Training and Testing Ranges for the Characterization of Energetic Munitions Constituents. SW846 Method 8330B uses the ISM principle with further grinding the samples to finer particles for analysis. In general, the whole sample (1.0 to 1.5 KG) air dried, sieved, and ground is spread into a grid formation and the sub-sample is collected using GY sampling technique. The sub-sample is typically in the 10-30g size and is ready for analysis. 4

5 State regulatory agencies have started to adopt and issue guidance for using MIS protocols at hazardous waste sites, not only for explosive but for other analysis as well. Alaska and Hawaii include volatile organics in state specific ISM guidance documents. The procedure for collecting the ISM sample for volatiles includes preservation in methanol. Here are some of the agencies with rules in regard to ISM; State of Alaska Department of Environmental Conservation, Division of Spill Prevention and Response, Contaminated Sites Program, Draft Guidance on Multi-Incremental Soil Sampling, March 2009 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, Section 4: Soil Sample Collection Approaches, November 2008 US Army Corps of Engineers Interim Guidance 09-02, 20 July 2009, Implementation of Incremental Sampling (IS) of Soil for the Military Munitions Response Program Ohio EPA Division of Emergency and Remedial Response, Standard Operating Procedure 2.6.1: Multi-Incremental Sampling for Soils and Sediments, January 2007 Interstate Technology Regulatory Council, Project Introduction: Incremental Sampling Methodology, July 2009 National Defense Center for Energy and Environment, Office of the Assistant Secretary of the Army for Installations, Energy and Environment, Concurrent Technologies Corporation, Multi-Incremental Fact Sheet ISM can lower site investigation costs by lowering the number of samples necessary to achieve an acceptable level of statistical confidence. Additionally, remedial efforts can be improved because of more accurate soil delineation. References FDEP [Florida Department of Environmental Protection], June 2013 (Draft).Incremental Sampling Methodology (ISM) Guidance. ITRC [Interstate Technology & Regulatory Council], 2012.Incremental Sampling Methodology. ISM-1. Washington, D.C.: Interstate Technology & Regulatory Council, Incremental Sampling Methodology Team, 5