170135_inorganicventures_flipping

3:3 Sampling and sub-sampling

Developing a Sampling Plan

In the development of a sampling procedure, the first step is to reexamine the problem defini9on (see Part 2). The analyst must review how the final results will be used and obtain an understanding of the characteris9cs of the sample popula9on.

For example "Has this industrial site been contaminated with Pb and Hg?" "Have Pb and Hg compounds been used on this site?" , "What type(s) of compounds were used?", "Where were these compounds stored?"

The analyst may determine that only 3-5 samples are needed in an area where drums that contained Pb and Hg compounds were placed. The other extreme would be to propose a random sampling over a 20 acre site, where 20 samples are pulled in a equally spaced geometric fashion. Other concerns pertain to the ‘normal' levels of Pb and Hg in the soil for that area where state and local environmental agencies would be contacted for baseline data.

3:4 Sampling and sub-sampling

Developing a Sampling Plan (cont.) By knowing the objective, the analyst is in a position to recommend sampling procedures that are designed to obtain a reliable answer.

A sampling plan should consider the following: • The objective of the analysis. • The liability/cost of a wrong decision. • The accuracy and precision requirements to obtain data that will allow for a correct decision to be made. • Whether the material has been sampled before. • The degree of homogeneity. Safety risks, site hazards, and product hazards. • Legal issues, including witnessing or permission grants. • Whether the material is in packages, heaps, bottles, railroad cars --i.e. - how the material is characterized.