Sampling Cost Advisor Instructions

In using SCA, the decision-maker first chooses the statistical sampling method that is appropriate based on the several assumptions required for selection (see EPA QA/G9, July 2000), for each sample design alternative. Then the decision-maker selects the corresponding spreadsheet for that statistical method. Next, the user enters into that spreadsheet several values for the decision error tolerances which may apply. That is, several (up to five for each) values for the alpha, beta, and delta (Gray Region) errors are entered into the spreadsheet, along with the Action Level and Standard Deviation (SD) of the Contaminant(s) Of Potential Concern (COPC) in question. At this point, the spreadsheet will have generated up to 75 samples sizes based on combinations of these alpha, beta, and delta values, for the given SD. Next, the unit cost of collecting one sample and the costs of performing each of the analytical methods on that one sample are entered into the spreadsheet to arrive at the Unit Sample Collection and Sample Analysis Cost. This value (USCSA$) is simply how much it will cost to collect and analyze one sample completely for all the project COPCs. The spreadsheet will now present the decision-maker with up to 75 sample sizes each showing the corresponding combination of error tolerances that were used to generate each sample size, along with the cost for each sample size.

Now, the decision-makers can "see" what degree of uncertainty (error tolerance) they will be "buying" for a given sampling and analyses cost. This then should be used to compare various combinations of error tolerances with the corresponding cost of S&A to arrive at both the number of samples and the S&A cost that the decision-makers feel are necessary to meet the project error tolerances (uncertainty). Further, given the "cost" of uncertainty (error tolerances), the cost of S&A can be compared with the cost of unnecessary remediation or unnecessary waste disposal in order to assist the decision-maker to select the most resource effective and defensible sampling design for the project.

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DOE DQO Program Manager, Dr Jeffrey W Day, (509) 372-4629.
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