Natural Gas Expert Witness Opines on Odorization System Defect

Jared Firestone

Written by
— Updated on January 6, 2022

Natural Gas Expert WitnessBackground

This case arises from Plaintiffs’ complaints of a “rotten egg” odor emitted from a natural gas facility neighboring their home. Defendants moved for summary judgment, asserting Plaintiff’s claims are barred by the Restrictive Covenant they signed in order to secure a Conditional Use Permit to build their home directly across the street from the gas facility. The Covenant prohibited “the permit grantee and successors in interest from filing complaints concerning accepted resource management practices that may occur on nearby lands including the normal usage of Pacific Gas Transmission Co.” Plaintiffs argued their current claims do not fall within the Covenant’s purview.

The parties’ dispute over the applicability of the Restrictive Covenant — and thus the viability of Plaintiffs’ claims — could be broken down into three questions, First, can a party who is not specifically named in the Restrictive Covenant claim its protection? Second, does the Covenant apply to activities or operations that commenced after it was signed? Third, do the circumstances underlying Plaintiffs’ claims constitute “normal usage”?

Expert Witness

Plaintiff’s natural gas odorization expert witness was David Robinson. Robinson is an engineer with relevant prior experience overseeing the construction and placement of natural gas pipelines, airfield fueling systems, hot pit refueling systems, and fixed hydrant systems.

Daubert Challenge

Defendants challenged the admissibility of the expert declaration of David Robinson. The Defendants challenged both Robinson’s qualifications to serve as an expert as well as the reliability of the methods used in drawing his conclusions.


(1) On Robinson’s Qualifications
While the Court found Robinson’s resume impressive, it noted that it did not indicate any familiarity with the subject of his proffered expert opinion: natural gas odorization. Given this apparent discord, the Court concluded that Robinson was not qualified to give expert testimony on the subject of natural gas odorization under the standards of Daubert, which require an expert to be an expert in the subject he or she testifies about.

(2) On Robinson’s Methods
The Court further concluded that even if Robinson was qualified to testify under Daubert, his declaration still must be excluded because it fails to satisfy the remaining expert testimony requirements. To assess the second requirement, reliability, the Court must ask “whether the reasoning or methodology underlying the testimony is scientifically valid.” Reliable testimony must be grounded “in the methods and procedures of science,” and signify knowledge beyond “subjective belief or unsupported speculation.”

Daubert identifies four factors that the Court may consider in assessing reliability, including (1) whether a theory or technique can be and has been tested; (2) whether a theory has been subjected to peer review and publication; (3) whether a “particular scientific technique” has a known or potential rate of error; (4) and whether the theory or technique enjoys general acceptance within the “relevant scientific community.”

Robinson based his opinion that the gas facility’s odorization system was operating abnormally and out-of-compliance with federal law on “testimony in this case” read in conjunction with some unnamed equipment guides and a “professional engineering manual.” Robinson did not provide adequate foundational information to demonstrate why the guides and manual form a sufficient basis for his opinions. It was not clear whether the referenced equipment guides discuss the specific models at-issue. As such, it was not clear whether Defendants had any reason to apply the guides’ standards to their operations. Nor was it clear whether the cited manual sets forth standards generally accepted in the gas odorization field. This omission was made all the more concerning by Defendants’ submission of evidence that the so-called “professional engineering manual” was actually an uncited, undated PowerPoint slideshow presentation. Robinson’s references to the “manual” linde up with this high-level slideshow’s bulletpoints.

Robinson provided no information to suggest that the concepts or standards presented in the guides and “manual” could be or had been tested, had been subject to peer review, had any known error rate, were generally accepted by the gas transmission industry, or were applicable to Defendants’ facility. Nor could the Court identify any other factors beyond those listed in Daubert that operate in favor of admissibility. There was simply no evidence that Robinson’s sources form a reliable basis for his opinions.

Beyond its lacking foundation, the declaration’s reliability suffered from two other fatal flaws. First, it contained “unsupported speculation.” Robinson advanced legal conclusions without adequate support. For instance, he opined that the frequency of odor releases constitutes a “nuisance” without indicating why he finds this to be true. Second, Robinson did not address evidence on the record that directly conflicted with his opinion testimony. Robinson concluded that one of the facility’s odorizers was operating in an abnormal manner despite ample evidence to the contrary

The Court also found that portions of Robinson’s declaration also failed to meet the final requirement of expert testimony: relevance. To be admissible under Rule 702, expert testimony must assist the average trier of fact. The Supreme Court characterizes this prong as “the ‘fit’ between the testimony and an issue in the case.” Testimony “fits” a case if it “logically advances a material aspect of the proposing party’s case.” Robinson’s declaration contained opinions that offered no insight into the issues of the case. Robinson concluded that Defendants were not in compliance with federal law because they did not odorize their gas to the point of being “readily detectable.” However, Plaintiffs asserted just the opposite – that odorant emissions are at nuisance levels.

In conclusion, Robinson’s declaration did not demonstrate to the Court that he was qualified to testify as an expert on natural gas odorization. Nor did he show that the sources of information underlying his testimony were reliable or valid. His declaration contained unsupported speculation and opinions that went against the weight of the record without making any effort to recognize or refute contrary evidence. For all these reasons, the Court found Robinson’s declaration to be inadmissible and ineligible to be considered in ruling on Defendants’ motions for summary judgment.

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