Expert Witness Profiler

Tag: Watershed

  • Geology Expert’s Testimony on Potential Alternative Sources Admitted

    Geology Expert’s Testimony on Potential Alternative Sources Admitted

    This case arises out of the contamination of surface waters and drinking water in Chattooga County, Georgia, with per- and polyfluoroalkyl substances known as “PFAS.”

    In essence, Plaintiff Earl Parris, Jr., alleged that the Defendants have contaminated his city’s water supply and thus his household water with PFAS. Parris is a resident of Summerville, Georgia, who receives running, potable water to his home from the Summerville Public Works and Utilities Department.

    The City of Summerville—which has intervened in this case—used Raccoon Creek, a tributary of the Chattooga River, as the main source of its municipal water supply. The Defendants are the following companies, which allegedly manufactured and supplied the PFAS discharged into Raccoon Creek: 3M Company (“3M”), Daikin America, Inc., E.I. du Pont de Nemours and Company, and The Chemours Company. Parris alleged that Raccoon Creek and—consequently, his household water—have been contaminated with PFAS by the Defendants. The Plaintiffs jointly filed a motion to exclude the testimony of 3M’s expert witness Andy Davis.

    Geology Expert Witness

    Andrew Owen Davis is a hydrogeologist who holds a Ph.D. in geology and has been involved in investigating a wide range of environmentally contaminated sites for over 40 years.

    Want to know more about the challenges Andy Davis has faced? Get the full details with our Challenge Study report.

    Discussion by the Court

    Davis concluded that no more than 0.2% of total PFAS load (or 2.9% of perfluorooctane sulfonate (PFOS) load) in the Raccoon Creek watershed originated from 3M’s products.

    This data is extrapolated from sampling data collected downstream of a farm where biosolids traceable to 3M were applied. Using data on the amount of biosolids applied and farm acreage, he calculated that 3M products could contribute approximately 0.052 mg/ton/day of PFOS. He then determined that biosolids traceable to 3M were deposited on two farms in the Raccoon Creek watershed, multiplied the total tons of biosolids applied to those farms by 0.052 mg/ton/day (with some adjustments), and concluded that 3M contributed “at most” 148 mg/day of 5,1000 mg/day (or 2.9%) of PFOS that made its way to Summerville’s water treatment plant.

    Factoring other types of PFAS, Davis found that 3M contributed 0.2% of total PFAS load. To account for the remaining PFAS concentration, Davis pointed to other potential sources of PFAS using existing PFAS literature and additional sampling data. According to Davis, these potential sources include the application of biosolids to farmland post-2000, poultry farms, cotton farms, septic systems, a fish hatchery, lumbar operations, fire retardant from a mill fire, and the household use of certain commercial products.

    Davis’ opinions regarding other ‘potential sources’ of PFAS in Raccoon Creek are speculative and unsupported by data

    Plaintiffs argued that Davis’ methodology amounts to speculation because (a) he relied on studies identifying PFAS in certain products but failed to verify whether those products were actually used in the Raccoon Creek watershed and (b) his sampling data does not adequately support ruling out 3M products as PFAS sources.

    The Plaintiffs advanced a variety of explanations for why Davis failed to prove that some of the potential alternative sources were at work or why they could not account for PFAS concentrations in the Raccoon Creek watershed. But these arguments spoke to the weight rather than admissibility of the evidence.

    For example, with regard to poultry farms, Davis found that several poultry farms in the Raccoon Creek watershed may contribute to PFAS levels because (1) there are several poultry farms in the area, (2) sampling data downstream of one of the farms revealed PFAS concentrations that did not contain the electrochemical fluorination signature of 3M’s products, and (3) studies have found PFAS in “[p]oultry farm bedding materials (litter)” made from recyclable materials and manure. The Plaintiffs did not challenge the sampling data results or the reputability of the studies.

    Instead, they argued that the sampling data and studies are not conclusive, as the PFAS concentrations may be caused by 3M-polluted water purchased by the farms from Summerville and the farms may not even use PFAS-based litter or manure.

    Here, the Court held that Davis’ methodology is adequately reliable for admissibility purposes. First, Davis’ report is not based on bare speculation regarding the potential non-3M PFAS sources. Davis takes his analysis one step further in identifying potential other sources of PFAS, but he is careful throughout his report to refer to these other sources as “potential” sources based on the available PFAS literature and his sampling data.

    Davis did not cherry-pick or conduct impermissible “results-based reasoning”

    The Plaintiffs took issue with Davis’ decision to base his calculation of the 3M-attributable PFOS load on only two farms where biosolids were applied, citing 3M’s and EPA’s supposed statements to the contrary.

    While the Plaintiffs may disagree with Davis’s decision to limit his 3M PFAS calculations to only two farms and may believe it contradicts 3M’s and the EPA’s statements, the Court found that Davis has provided a sufficient basis for his methodological choice.

    According to Davis, he limited his 3M PFAS calculations to two farms because he determined that those farms were the only two where biosolids were applied prior to 2001.

    Regarding cherry-picking certain reports, the Court agreed with the Defendants that Davis is free to rely on facts presented in published reports as well as his own experience and knowledge in forming his opinions where he does not agree with other facts presented in those reports.

    Held

    The Court denied the Plaintiffs’ motion to exclude the testimony of Andy Davis.

    Key Takeaway

    An expert report is not automatically unreliable merely because it agrees with some aspects of an existing report and not others. Therefore, Davis has shown his methodology is sufficiently sound and that it is “properly grounded, well-reasoned, and not speculative.”

    Please refer to the blog previously published about this case:

    Polymers Expert Allowed to Opine on PFOS Sources

    Case Details:

    Case Caption: Parris V. 3M Company
    Docket Number: 4:21cv40
    Court Name: United States District Court, Georgia Northern
    Order Date: March 16, 2026
  • Polymers Expert Allowed to Opine on PFOS Sources

    Polymers Expert Allowed to Opine on PFOS Sources

    This case arises out of the contamination of surface waters and drinking water in Chattooga County, Georgia, with per- and polyfluoroalkyl substances known as “PFAS.”

    In essence, Plaintiff Earl Parris, Jr., alleged that the Defendants have contaminated his water with PFAS. Parris is a resident of Summerville, Georgia, who receives running, potable water to his home from the Summerville Public Works and Utilities Department.

    The City of Summerville—which has intervened in this case—used Raccoon Creek, a tributary of the Chattooga River, as the main source of its municipal water supply. Parris alleged that Raccoon Creek and—consequently, his household water—have been contaminated with PFAS by the Defendants. At present, Parris and Summerville jointly moved to exclude the opinion testimony of Defendant 3M’s expert, Maureen Reitman.

    Polymers Expert Witness

    Maureen Theresa Fahey Reitman, Sc.D. has been practicing in the field of polymer science and engineering for more than 30 years.

    She has a Doctor of Science in Materials Science and Engineering, with a thesis in the field of polymers, from MIT. She is also a licensed Professional Engineer in the state of Maryland and a Fellow of the Society of Plastics Engineers.

    Get the full story on challenges to Maureen Reitman’s expert opinions and testimony with an in-depth Challenge Study.

    Discussion by the Court

    Relevancy and Likelihood of Confusion

    Plaintiffs asserted that Reitman failed to identify any perfluorooctane sulfonate (PFOS)-containing products at the Mount Vernon Mill or the Trion Water Pollution Control Plant (“Trion Plant”) other than 3M’s product.

    The Court agreed with 3M that Reitman’s opinions as to other possible sources of PFAS and PFOS in the Raccoon Creek watershed are relevant to the issue of causation. Although it is 3M’s burden to establish the relevance and reliability of their expert’s opinions, it is ultimately the Plaintiffs’ burden at trial to prove the causal connection between their alleged injuries and the Defendants’ alleged actions.

    Here, 3M sought to introduce evidence undermining the Plaintiffs’ causation evidence by showing that there were other possible causes of the Plaintiffs’ injuries. Thus, the Plaintiffs’ argument that Reitman cannot determine “to what extent, if any, a participant in the global supply and use network for PFAS released a particular substance into the environment at issue” entirely missed the mark—the fact that Reitman is testifying she cannot make this determination is the whole point of introducing her testimony.

    3M intended to rely on this testimony to argue that the Plaintiffs cannot prove its product is the cause of the alleged PFAS contamination in the Raccoon Creek watershed.

    The Plaintiffs also sought to exclude Reitman’s opinions under Federal Rule of Evidence 403, arguing that her testimony about PFOS sources manufactured abroad will confuse the jury because such sources are irrelevant to their claims. Because Reitman’s testimony is relevant and will be helpful for the jury, the extraordinary remedy of exclusion under Rule 403 is unwarranted here.

    Reliability

    Plaintiffs asserted that Reitman admitted she does not have any data indicating PFOS sources besides 3M’s product are present in the Raccoon Creek watershed, yet she seeks to testify that other possible sources exist.

    However, Reitman’s report explains the reasons why the identification of PFOS and PFAS “in an environmental sample is not sufficient to identify the original source of production.” Further, she explains why this is true regardless of the characteristics in a sample associated with electrochemical fluorination (ECF), a process that 3M is known to have utilized in processing PFOS.

    And she provided testimony critical to 3M’s causation defense that the Plaintiffs have not provided an appropriate scientific basis for excluding other possible suppliers of the specific PFAS at issue due to the potential contributions of products associated with global supply chains.

    The fact that Reitman’s opinions may undermine the causation evidence the Plaintiffs intend to present does not make them unreliable; instead, the Plaintiffs’ concern goes to the weight and credibility of the evidence. The Plaintiffs will have the opportunity to cross-examine Reitman at trial, where their concerns will be more appropriately addressed.

    Held

    The Court denied the Plaintiff and Intervenor-Plaintiff’s joint motion to exclude the opinions of Maureen Reitman.

    Key Takeaway

    In the Court’s view, the Plaintiffs did not truly challenge the reliability of Reitman’s opinions, but instead challenged the content of her opinions. But the Court’s inquiry at this stage “must be solely on principles and methodology, not on the conclusions that they generate.”

    Case Details:

    Case Caption: Parris V. 3M Company
    Docket Number: 4:21cv40
    Court Name: United States District Court, Georgia Northern
    Order Date: March 09, 2026