Soil Sampling for Heavy Metals Pre- and Post-Job: What Do We Really Know?

Soil Sampling and Project Specifications

Routinely, project specifications have adopted SSPC’s soil sampling procedure in Technology Update No. 7 (Section 10 Ground (Soil) Sampling & Analysis) without appreciating the limitations of what has been specified. Similarly, contractors have in some cases adopted the SSPC soil-sampling procedure even when it is not specified.

soil sampling

More concerning is when the specification states that if the post-job soil sample is X percent above the geometric mean, soil remediation will be required. This is problematic because Technology Update 7 specifically states that it “is not suitable for site characterization purposes.”

If TU7 is not to be used to characterize a site, should it be used as a means to require remediation? The answer is clear: It should not be used in that fashion. The SSPC Technology Update No. 7 procedure should be viewed as a qualitative test.

TU7 advises sending in soil sample plugs to a lab for analysis, but the results reported by the lab can only reliably relay the presence or absence of a given analyte in the surface soil. A result (value in parts per million or milligrams per kilogram) will be generated by the lab, but does it represent the true concentration of the area it is purported to reflect? The answer is no.

This is not a knock on the SSPC soil-removal and analysis procedure. There is utility in the procedure being easy to use and easy to apply in the field to determine if metals are present or not. In fact, TU7 filled a much-needed knowledge gap in the industry when it was introduced. It is not SSPC’s fault the procedure has been adopted and used inappropriately.

Soil Sampling (Risk Characterization)

For risk-characterization purposes, providing defensible, quality environmental data will require a discrete soil sampling method that can reliably measure the accuracy, precision, completeness, representativeness and comparability for both the field sampling and the analysis of the samples.

The objective of taking pre-job soil samples is presumably to generate data to quantify the presence or absence of lead (and other heavy metals). To meet this objective, samples removed during the collection stage must be defensible to meet this objective. Guide TU7’s soil sampling procedure is silent regarding these measurement quality objectives.

It is apparent that the Ground (Soil) Sampling & Analysis procedures outlined by Technology Update No. 7 is not intended for risk-characterization purposes, and is clearly inadequate to determine if cleanup should be required on a project site after the completion of a project. As a result of the lack of measurement quality objectives, the interpretation of pre and post soil sampling results obtained using TU7 methodology should be taken with a grain of salt.

The TU7 soil-sampling procedure has served a very useful purpose in the industrial abrasive blasting and painting industry; however, recognize that using this document for risk characterization purposes will arguably yield scientifically indefensible environmental data.

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