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March 2020 – Round and Around

‘Round and Around We Go – Rounding of Data in NJ

Like a toy top, the New Jersey Department of Environmental Protection (NJDEP) is spinning on rounding rules, with Licensed Site Remediation Professionals (LSRPs) and the regulated community unclear where it will stop.

On February 18, 2020, NJDEP released a listserv, “Notice Concerning the Use of Rounding of Analytical Data as a Method to Determine Compliance with Remediation Standards.” The NJDEP stated in the Notice that it does not have an official policy regarding rounding of data as a method of compliance, nor are there current laws or rules that address rounding as a method of compliance. Why is this an issue? Because the laboratory and data user community are not consistent on rounding or reporting of significant figures.

Let’s say we have Bad Chemical X with an action limit of not to exceed 1 ppm. Let’s say in the ideal world, two laboratories analyzed the sample and achieved the same result. Laboratory A reported Bad Chemical X at 1.4 ppm (because its Quality Assurance [QA] Plan dictates two significant figures). Laboratory B reported Bad Chemical X at 1 ppm (because its QA Plan dictates one significant figure). One result requires remediation, the other does not. Same sample, same data result, different reporting rules.

A second issue is the NJDEP may not necessarily rely on the professional judgment of the LSRPs and the regulated community. Interim rounding guidelines were announced in the Notice that include, data associated with Immediate Environmental Concern and Vapor Concern cases should not be rounded (i.e., take whatever the laboratory gives you, regardless of data accuracy) and for all other data, use “independent professional judgment in determining if rounding of analytical data is appropriate.” NJDEP dictates that if data are rounded, the technical justification for doing so must be contained in the appropriate document submittal.

It is NJDEP’s intent to amend the “Technical Guidance for the Attainment of Remediation Standards and Site-Specific Criteria,” but if the interim guidelines of how to round are a glimpse of where this spinning top will stop, we are in for data vertigo (uncertainty and dizziness).

Avoid experiencing this data vertigo by relying upon the technical assistance of the Chemists at Environmental Standards. LSRPs and the regulated community often seek our help in assessing data quality; and here is another reason: assessing the appropriateness of your data’s significant figures and rounding. We can help you avoid dizzy data confusion.


Lydia M. Work, LRS

Principal Chemist