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Sampling Questions

Test Methods:  Frequently Asked Questions

Decontamination of Sampling Equipment

Question: Where can I find information on decontamination procedures for sampling equipment?

Answer: There are many references, but here are a few good ones for decontamination of waste sampling equipment:

ASTM D 5088 - 02(2008) Standard Practice for Decontamination of Field Equipment Used at Waste Sites Exit EPA

USEPA. 1994. "Sampling Equipment Decontamination." Environmental Response Team SOP #2006, Revision #0.0. Edison, NJ.

USEPA. 1996. Environmental Investigations Standard Operating Procedures and Quality Assurance Manual. Region 4, Science and Ecosystem Support Division. Athens, GA.

For decontamination of groundwater sampling equipment, see:

USEPA. 1992. RCRA Ground-Water Monitoring: Draft Technical Guidance. EPA/530/R-93/001. Office of Resource Conservation and Recovery. Washington, DC.

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Drum Sampling

Question: Where can I find references regarding drum sampling?

Answer: Several references are available on drum sampling: Chapter Nine SW-846 (see page NINE-73) includes guidance on sampling drums and similar containers. The following EPA documents also include information on drum sampling:

USEPA. 1994. "Drum Sampling." Environmental Response Team SOP #2009, Revision #0.0. Edison, NJ.

USEPA. 1996. Environmental Investigations Standard Operating Procedures and Quality Assurance Manual. Region 4, Science and Ecosystem Support Division. Athens, GA. (PDF) (24 pp, 1.03 MB, about PDFs )

Also, the ASTM Exit EPA has published several guides that include information on drum sampling including:

ASTM D 5679-95a. 1995. Standard Practice for Sampling Consolidated Solids in Drums or Similar Containers Exit EPA

ASTM D 5680-95a. 1995. Standard Practice for Sampling Unconsolidated Solids in Drums or Similar Containers Exit EPA

ASTM D 5743-97. 1997. Standard Practice for Sampling Single or Multilayered Liquids, With or Without Solids, in Drums or Similar Containers Exit EPA

ASTM D 6063-96. 1996. Standard Guide for Sampling of Drums and Similar Containers by Field Personnel Exit EPA

ASTM D6232 - 2008 Standard Guide for Selection of Sampling Equipment for Waste and Contaminated Media Data Collection Activities Exit EPA

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Composite Sampling

Question: We have to sample a very large number of drums. Is it practical to composite samples from different drums?

Answer: Composite sampling is a strategy in which multiple individual or "grab" samples (from different locations or times) are physically combined and mixed into a single sample so that a physical (rather than mathematical) averaging takes place. Thus, for a well-formed composite, a single measured value should be similar to the mean of measurements of the individual components of the composite. The analysis results from multiple composite samples can be used to perform the statistical calculations described in Chapter Nine. Multiple composite samples can provide improved sampling precision and reduce the total number of analyses required compared to noncomposite sampling. This strategy is sometimes employed to reduce analysis costs when analysis costs are large relative to sampling costs.

If the objective of the waste characterization effort is to classify all of the drums collectively as either hazardous or nonhazardous, then collection of multiple composite samples could be employed to reduce analysis costs. This approach, however, is not recommended if there is substantial drum-to-drum variability such that one or more drums should clearly be classified as hazardous and others as nonhazardous. If some of the drums might be classified as hazardous when characterized individually, then we recommend you make a waste classification decision on each drum to avoid the possibility of mixing hazardous waste with nonhazardous waste.

Composite sampling should not be used if the integrity of the individual sample values changes because of the physical mixing of samples. The integrity of individual sample values could be affected by chemical precipitation, exsolvation, or volatilization during the pooling and mixing of samples. For example, volatile constituents can be lost upon mixing of samples or interactions can occur among sample constituents. In the case of volatile constituents, compositing of individual sample extracts within a laboratory environment may be a reasonable alternative to mixing individual samples as they are collected.

Note that compliance with the land disposal regulation (LDR) numeric treatment standards is to be determined using "grab" samples rather than composite samples. Grab samples processed, analyzed, and evaluated individually normally reflect maximum process variability, and thus reasonably characterize the range of treatment system performance. In those cases in which only composite data were available to develop a treatment standard, the EPA used these data. For wastes for which the standards are based on composite data, enforcement of the standard is to be based on composite data.

A detailed discussion of the advantages and limitations of composite sampling is presented in the Standard Guide for Composite Sampling and Field Subsampling for Environmental Waste Management Activities (ASTM D 6051-96).

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Groundwater Sampling

Question: Where can I find information on sampling groundwater?

Answer: Guidance on groundwater sampling can be found in EPA's "RCRA Groundwater Monitoring: Draft Technical Guidance," published by the Office of Resource Conservation and Recovery, EPA/530/R-93/001, NTIS PB 93-139350. The document updates Chapter Eleven of SW-846.

Additional updated information on ground-water sampling can be found in "Low-Flow (Minimal Drawdown) Ground-Water Sampling Procedures" EPA/540/S-95/504 April 1996.

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Wipe Sampling

Question: Where can I find wipe sampling methods in SW-846?

Answer: Wipe sampling is only addressed in SW-846 in the context of laboratory safety concerns relative to dioxins and furans, and a very limited discussion of wipe sampling techniques appears in Appendix A to Method 8290A. However, EPA does not recommend that the procedure there be extended to other analytes or other situations.

While wipe sampling has been described in the open literature, one of the biggest problems is that it is very difficult to interpret the results. By its very nature, the analysis of whatever material is used to wipe a surface (often filter paper wet with a solvent) yields the mass of the analyte(s), for example nanograms of dioxin or micrograms of another analyte. However, there is no straightforward way in which to convert that mass into a concentration per unit area, nor any good way in which to compare results from different wipes, except to say that one wipe picked up more material than another. If the surfaces that are wiped have different characteristics, for example a smooth metal surface versus a rough concrete block, there is no way to judge the efficiency of the wiping process itself. Therefore, use caution in interpreting the results of wipe samples.

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