Engineering Expert’s Theory of Damages Excluded
Posted on October 30, 2025 by Expert Witness Profiler
Plaintiff Leflore County Board of Supervisors filed suit against Meritor over a state-approved waste disposal that occurred almost two decades ago.
In 2006, Meritor’s predecessor, ArvinMeritor, sent some waste to Plaintiff’s landfill (the “Landfill”) as part of a state-approved cleanup of the Moose Lodge Road Disposal Area (“MLRDA”). And now, almost two decades later,
Plaintiff claimed that the MLDRA waste it received as part of that state-approved cleanup was wrongfully characterized as non-hazardous.
Plaintiff held Meritor responsible for all costs necessitated by the waste disposal at the landfill.
Defendant Meritor, Inc. filed a motion to strike the second supplemental report of Plaintiff’s expert D. Scott Simonton.
Engineering Expert Witness
David Scott Simonton is a Registered Professional Engineer with over thirty (30) years of professional experience in State environmental and public health protection regulatory agencies, private consulting and academia.
Discussion by the Court
The Plaintiff initially submitted Simonton’s expert report on November 25, 2024, which was the deadline for the Plaintiff’s expert designation imposed by the original Case Management Order. Notably, this initial report consisted of a cost estimate of $170,382.50 for “waste characterization,” based on the Plaintiff’s belief that Meritor had disposed of hazardous wastes in a certain limited area of the Leflore County municipal landfill.
Subsequently, on January 29, 2025, after Simonton’s initial expert report was produced, the parties deposed Leflore County’s landfill operator, Waste Connections, whose representative testified that it had no way to determine where the allegedly hazardous waste had been disposed of within the landfill. This testimony, in turn, formed the alleged basis for the opinion offered in Simonton’s second supplemental report.
Following the Waste Connections deposition, Simonton submitted his first supplemental report on April 15, 2025, and later, his rebuttal report on June 5, 2025. However, neither report included a new or revised cost estimate that accounted for Waste Connections’ position that the location of the contaminated soils could not be determined. Thereafter, Meritor deposed Simonton on June 30, 2025, and the discovery period closed on August 8, 2025.
Finally, on August 29, 2025, the Plaintiff submitted Simonton’s second supplemental report—the subject of the present motion—which included a “Remedial Investigation cost estimate” totaling $3,163,902.50. This report sought to address the alleged uncertainty regarding the location of the contaminated soil within the Leflore County municipal landfill and justified the need for an expanded investigation involving increased sampling.
Analysis
The Plaintiff’s expert designation deadline was November 25, 2024, and any supplement to Simonton’s expert report was due no later than the discovery deadline of August 08, 2025.
I. Whether the second supplemental report contains new opinions
The Plaintiff argued that the estimate in the second supplemental report “was merely a recalculation of [Simonton’s] mathematical formulas based on new information, i.e., Meritor’s lack of knowledge of where it caused the hazardous wastes to be dumped.” However, Meritor contended that the supplemental report introduced “an entirely new theory of damages” that had not been previously disclosed and lacked good cause. The Court agreed.
Simonton’s second supplemental report presented a Remedial Investigation (“RI”) cost estimate based on entirely new criteria and considerations—all known to the Plaintiff as early as January 2025 but not included in the initial or previously supplemented reports.
Regardless of whether the earlier reports contained opinions about the need for an RI (a point the parties dispute), the second supplemental report offered an entirely new cost estimate based on Waste Connections’ opinion that the location of the contaminated soils at the municipal landfill could not be determined. This stood in contrast to the prior assumption that Meritor had disposed of hazardous wastes only in a certain limited area. As a result, the Plaintiff’s attempt to introduce new opinions through an untimely supplement was deemed improper.
II. Whether the new opinions are substantially justified or harmless
The Plaintiff offered no explanation for the failure to supplement Simonton’s opinion at any point during the seven-month period after Waste Connections’ deposition and before the expiration of the discovery deadline. This delay certainly mitigates against the alleged importance of the opinion. Despite the Plaintiff’s arguments to the contrary, the prejudice to Meritor is clear: the second supplemental opinion is neither a minor amendment nor a recalculation. The discovery period is closed, and the motions deadline has passed. Meritor has had no opportunity to seek discovery regarding this opinion or have its own expert review and respond in their report. Finally, to continue the trial setting and reopen discovery to mitigate the prejudice to Meritor would require the Court to ignore the Plaintiff’s failure to establish the first three factors.
The Court concluded the untimely disclosure of Simonton’s second supplemental report was not substantially justified or harmless.
Held
The Court granted Meritor’s motion to strike the second supplemental report of Plaintiff’s expert D. Scott Simonton.
Key Takeaway:
The second supplemental report of Simonton contained opinions markedly different from those set forth in the original, first supplemental, and rebuttal reports and was made beyond the permissible deadline for supplementing expert disclosures under Rule 26.
Case Details:
| Case Caption: | Leflore County Board Of Supervisors V. Meritor, Inc. Et Al |
| Docket Number: | 4:24cv33 |
| Court Name: | United States District Court, Mississippi Northern |
| Order Date: | October 29, 2025 |
