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.
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.”
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 |
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