Do We Really Need All the Quality Assurance/Quality Control Samples in Groundwater Monitoring?

Oral Presentation

Prepared by M. Lupo1, M. Wilken2, D. Capria1, L. Austrins1, K. Abbott1, M. Klar1
1 - Arcadis, 10205 Westheimer Rd Ste 800,, Houston, TX, 77042, United States
2 - Dow Chemical Company, Dow Chemical 1790 Building, Washington St, MI, 48640, United States


Contact Information: Mark.Lupo@arcadis.com; 713-953-4722


ABSTRACT

Quality Control/Quality Assurance (QA/QC) samples have been used over the past four decades to help identify false positive detections of groundwater contaminants. However, these QA/QC samples may no longer be necessary given improvements in the techniques used by laboratory and field professionals over the years, as well as improvements in the statistical methodologies used in the data analysis. This hypothesis was tested by examining data collected from 2008 to 2018 at nine facilities in Texas operated by The Dow Chemical Company. The data base contained 9,635 records identified as equipment blanks, field blanks, and trip blanks. There were 88 detections, all but 20 of which were of common laboratory contaminants.
The 20 detections in blanks were compared against site samples collected on the same day as the blank. The number of detections in site samples were counted that were within a factor of five of the concentration in the respective blank. Only nine such cases were identified involving six blank detections, but none of the cases involved an exceedance of the regulatory standard.
In 2009, the United States Environmental Protection Agency issued improved guidance for the statistical analysis of groundwater data at RCRA facilities. This guidance includes resampling strategies for controlling the site-wide false positive rate. Thus, the USEPA has provided resampling options as a protection against false positive detections at the same time QA/QC blanks have provided less frequent identification of false positives.
In conclusion, improved methodology in the field, laboratory, and statistical analysis have rendered these blanks obsolete as a protection against false positive exceedances of groundwater standards.