Formatted Title
Review of a Demonstration of Method Applicability for the Approval of ASTM Method D8421 to Support DoD PFAS Remedial Investigation Work
Background/Objectives
The goal of this presentation is to present a thorough review of several Demonstration of Method Applicability (DMA) studies that were conducted to evaluate the performance and gain approval for the use of ASTM Method D8421 to support the Army National Guard’s (ARNG) PFAS Remedial Investigation (RI) projects. The rationale and benefits of using a lower cost, fast screening analytical method in conjunction with the higher cost and slower definitive method (US EPA Draft Method 1633) will be presented. This hybrid approach is rooted in the TRIAD strategy (USEPA, 2001), which was developed to enable reliable application of screening methods with definitive testing to improve the resolution of sampling, reduce the duration of environmental site investigation and remediation projects and improve the accuracy of conceptual site models.
Approach/Activities
The subject DMAs used two tiers of statistical analyses to compare the two methods. The base level of statistics was Ordinary Least Squares (OLS) regression with calculation of R2 and slope as well as evaluation of relative percent differences (RPD). Additionally, a statistical evaluation was also completed to further evaluate the reliability of decision making relative to risk-based screening level data using a false positive/false negative assessment around various water and soil site characterization action levels. At each of the ARNG sites during the initial groundwater and soil sampling activities, 100% of the samples were analyzed using EPA Draft Method 1633 and ASTM D8421. The goal was to provide a minimum of approximately 25 sample screening level results for each matrix so that a statistically significant data set would be available for the DMA. To ensure robustness of the data sets, sample selection targeted samples having a wide range of concentrations over a range of different soil types. Special attention was given to samples having elevated suspended solids and assessing how the differing sample preparation methods for the screening and definitive methods may have affected the results.
Results/Lessons Learned
The results of this DMA study will be presented and will include a discussion of the suitability of using screening level data for these (and future) RI projects as well as an overview of several sampling strategies for optimizing the value of these hybrid data sets.