McHugh, T.E., P.R. Kulkarni, C.J. Newell, and S.L. Britt.
ESTCP Project ER-201209, 50 pp, 2015

The project purpose was to (1) validate sample collection methods and procedures that minimize variability in groundwater monitoring results, and (2) validate improved methods to optimize monitoring frequency and assess long-term concentration trends that better account for short-term variability in groundwater monitoring results. The field demonstration was conducted in eight monitoring wells each at a Texas and a California demonstration site. Results indicated that the sample method (except active no-purge) has only a modest impact on monitoring variability and concentration, suggesting sampling methods could be selected based on factors such as cost, ease of implementation, and sample volume requirements rather than concerns regarding data quality. Low-flow standard (purging to parameter stability) and low-flow alternative (small volume) showed the lowest variability at both sites. Results were consistent between the two sites except for the active no-purge (HydraSleeve) method, which was more variable at the California site than the Texas site. Low-flow small-volume purge and passive no-purge (SNAP sampler) were the two most effective sampling methods based on the combined goals of minimizing monitoring cost and minimizing variability in monitoring results. https://www.serdp-estcp.org/content/download/36932/352841/file/ER-201209-CP.pdf