Letter to the Editor The Western States Petroleum Association (WSPA) appreciates GRAÕs interest in stimulating further scientific debate on the role of purging in groundwater sampling Technical publications such as yours play a critical role in the continuing education of the scientific community. In that capacity, you are responsible to the scientific community, the regulatory community and the public at large to report new information in an objective manner. Unfortunately, your article, ÒRegulatory Board Duped by Flawed StudyÓ (Summer, 1997 edition of HydroVisions), disregards this responsibility by presenting a strikingly one-sided treatment of WSPAÕs research (ÒThe California Groundwater Purging Study for Petroleum HydrocarbonsÓ). Certainly, GRA is doing a disservice to its readership by perpetuating a number of misconceptions and misinterpretations about the intent and recommendations of WSPAÕs study. Although we have previously attempted to address many of the specific concerns raised in your article, for the benefit of your readers and in the interest of motivating a more balanced and productive scientific debate on this issue, this letter and the following attachments are intended to revisit these concerns in a more definitive fashion. The decision to evaluate bailer and vacuum truck purging methods continues to be a focal point for criticism of the study design and findings by some reviewers. In previous correspondence with Dr. Michael Barcelona (University of Michigan), WSPA emphasized that the widespread use of bailers and vacuum trucks necessitated their inclusion in the study to ensure that study findings were applicable in terms of the current regulatory environment. WSPA also acknowledged without question that low-flow purging through dedicated pumps in depth-discrete wells can yield samples which more closely resemble formation water than samples taken by bailer or vacuum truck purging methods. An important point that was overlooked in your article is the fact that 47% of the samples in WSPAÕs data set were obtained from submersible pumps. Not surprisingly, there is less variability in this data than in the bailer and vacuum truck data. However, a threshold question which was a primary focus of WSPAÕs research and which continues to be obscured by this debate, was whether any differences observed in constituent concentrations before and after purging would be significant enough to affect a regulatory decision (i.e. a petition for site closure). Our analysis suggests that this is generally not the case, even where bailers are used for purging. Certainly, the incremental sampling prevision attributed to dedicated pumps does not appear to provide adequate justification for maintaining purging during routine groundwater monitoring. Perhaps the most unfortunate aspect of your article is the conclusion that regulatory agencies choosing to implement some form of direct (no-purge) sampling have rushed to judgement based on ÒflawedÓ science. This conclusion is misdirected and highly speculative. Rather, it is our understanding that these agencies have carefully considered the same core questions that motivated WSPAÕs study and have come to the conclusion that the study findings do provide a reasonable basis for discontinuing purging during routine groundwater monitoring where sites meet the conditions specified in the report. In recognition of the uncertainty in the data set, some agencies have conditioned their policies to require responsible parties to reinstate purging for a single sampling event to validate direct sampling data before a final regulatory decision is made. This approach appropriately balances emerging scientific information with resource protection and economic concerns and in so doing seems far more rational than making a wholesale and potentially unnecessary commitment to an alternative purging technology. The following attachments speak to specific technical issues raised in your article. WSPA hopes that this correspondence will help resolve much of the confusion surrounding application of the study findings. We urge GRA to print this letter and the attachments in their entirety in a subsequent edition of HydroVisions. In addition, we encourage your readers to draw their own conclusions based on a full reading of WSPAÕs report, available on internet at http://www.secor.com/purge.htm. If you have any questions, please contact Paul Horton of Secor at (510) 686-9780, Ralph Moran of ARCO at (213) 486-1257 or me at (916) 498-7753. Sincerely, Attachments Attachment 1 Comment: Response: Comment: Response: Comment: Response: GRA has made available to its members copies of Dr. Barcelona comments. If you would like a complete set of his comments and annotations to WSPA’s study, submit $5.00 to cover postage and reproduction costs to: GRA, P.0. Box 1446, Sacramento, CA, 95812. My apologies for using the word “Duped.” A less demeaning word could have been used. Floyd Flood |