Patrick D. Reilly, Gina M. Stanaway, Erstad & Riemer, P.A., 1000 Northland Plaza, 3800 West 80th Street, Minneapolis, MN 55431 (for respondent)

Considered and decided by Harten, Presiding Judge, Schumacher, Judge, and Peterson, Judge.

PETERSON, Judge

Appellant Tiller Corporation, a Minnesota corporation, d/b/a Barton Enterprises, Inc., brought this action for negligence and breach of warranty in a bailment relationship against respondent TexPar Energy, Inc., alleging that material stored by TexPar in tanks owned by Barton caused severe corrosion to the tanks. A jury found TexPar liable, but the district court concluded that Barton had not presented sufficient evidence to prove causation and granted TexPar's motion for JNOV. We affirm.

Barton operated a petroleum storage facility, consisting of 12 carbon-steel storage tanks of varying capacities. TexPar stored materials at the facility in tanks owned by Barton. TexPar was in the wholesale bulk fuel oil business, selling products ranging from natural gas to residual fuel oil, the product left over at the end of the crude oil refining process. TexPar bought residual fuel from 35-40 refineries, and each refinery produced a different residual fuel depending on the original crude oil and the refining process used.

TexPar blended the residual fuels it purchased with cutter stock in order to meet customer specifications regarding sulfur content, flash point, BTUs, API gravity (weight), and viscosity. Cutter stock can range from expensive number-two heating oil to inexpensive number-six fuel oil, a residual fuel oil. Beginning in August 1995, TexPar blended the number-six fuel oil that it was storing at Barton's storage facility with a cutter stock obtained from the Trumball Asphalt Division of Owens-Corning Fiberglass. Barton alleges that the Trumball cutter stock was highly acidic and caused severe corrosion damage to two of Barton's storage tanks. The Trumball cutter stock was used at Barton's storage facility from August 18, 1995, until March 4, 1996.

The Trumball cutter stock was used in tanks six, eight, and nine. A leak occurred in tank nine in March 1996, when product was pumped from tank eight into tank nine. Barton emptied tanks eight and nine and discovered corrosion in both tanks. The evidence indicates, and the parties do not dispute, that the corrosion occurred at a level above where TexPar's product had been stored. There is no allegation of damage to tank six.

Tanks eight and nine were each 48 feet high and 61 feet in diameter, and each had a one-million-gallon storage capacity. Both tanks consisted of a bottom, six rings of carbon-steel shell plates, each approximately eight feet high, and a carbon-steel roof supported by a series of internal steel beams and rafters. The roofs of both tanks, the top four rings of tank nine, and the top ring of tank eight had to be replaced. No damage occurred to the floor or bottom rings of either tank. Barton presented evidence that, based on the expected lifespan of the tanks, both of which were constructed in 1980, the corrosion damage occurred prematurely.

Before storing the Trumball cutter stock at Barton's facility, TexPar had it tested for API gravity, viscosity, BTUs, sulfur content, carbon content, ash, flash point, water, and sediment. TexPar, however, did not test the corrosiveness of the Trumball cutter stock, either by itself or after it was blended with the residual fuels in Barton's tanks. Nor did TexPar provide Barton with a material-data safety sheet for the Trumball cutter stock. After Barton discovered the damage to tanks eight and nine, it obtained a material-product data sheet for Trumball cutter stock. The data sheet showed that Trumball cutter stock could be highly acidic, with a pH factor ranging from 1.5 to 5.0.

Barton did not conduct any testing on the Trumball cutter stock that it claimed damaged its tanks but did have testing done on the sludge remaining at the bottom of tank nine after it was emptied. Test results showed that the pH factor of the sludge was 1.6, which is highly acidic, and that the sludge contained both hydrochloric and sulfuric acids. Daniel Olson, the person who performed the testing, testified that hydrochloric acid is among the most corrosive of industrial products and that he was not aware of a steel that was resistant to corrosion by hydrochloric acid.

During the fall of 1995, tanks eight and nine had been emptied to permit the installation of new double bottoms. At that time, two Barton employees conducted visual examinations of the tanks and observed no abnormal corrosion. The employees conducted the visual inspections by standing on the floor on the inside of each tank and looking up. One of the employees, Dennis Sauer, conceded that standing on the tank floor and looking up was like "you were in the superdome." Donald Johnson, a civil engineer with degrees in mathematics and physics, testified that a person must get physically close to corrosion to see it and that it was not possible to adequately inspect a fuel storage tank by standing at the bottom and looking up.

The court may grant judgment notwithstanding the verdict when the verdict is against the overwhelming evidence so "that reasonable minds cannot differ as to the proper outcome." The granting of JNOV is a pure question of law. This court is not bound by a trial court's decision on a purely legal issue.

Bruchas v. Preventive Care, Inc., 553 N.W.2d 440, 442 (Minn. App. 1996) (quoting Lamb v. Jordan, 333 N.W.2d 852, 855 (Minn. 1983)) (citations omitted).

A motion for judgment notwithstanding the verdict admits every inference reasonably to be drawn from the evidence as well as the credibility of the testimony for the adverse party.

Seidl v. Trollhaugen, Inc., 305 Minn. 506, 507, 232 N.W.2d 236, 239 (1975).

This case was submitted to the jury on theories of negligence and breach of warranty in a bailment relationship. Causation is an element of both causes of action. See Johnson v. State, 553 N.W.2d 40, 49 (Minn. 1996) (proximate cause is an element of negligence); Miller v. Macalester College, 262 Minn. 418, 428, 115 N.W.2d 666, 673 (1962) (bailor liable in negligence for providing unsafe equipment to bailee).

To prove causation, plaintiff must present evidence

which affords a reasonable basis for the conclusion that it is more likely than not that the conduct of the defendant was a substantial factor in bringing about the result. A mere possibility of such causation is not enough; and when the matter remains one of pure speculation or conjecture, or the probabilities are at best evenly balanced, it becomes the duty of the court to direct a verdict for the defendant.

Rullman v. Fisher, 371 N.W.2d 588, 590 (Minn. App. 1985) (quoting W. Prosser, Handbook of the Law of Torts § 41, at 241 (4th ed. 1971)). "Proof of a causal connection must be something more than merely consistent with complainant's theory of the case." E.H. Renner & Sons, Inc. v. Primus, 295 Minn. 240, 243, 203 N.W.2d 832, 835 (1973).

Barton presented evidence that the Trumball cutter stock that TexPar stored in its tanks was highly acidic and that highly acidic material causes corrosion to steel. But because the evidence indicated that the corrosion damage to Barton's tanks occurred in the atmosphere area above the level where material was stored, evidence that the material stored in the tanks was highly acidic was insufficient to prove causation. It was necessary for Barton to demonstrate that a highly acidic material can cause corrosion in the atmosphere above the level where the material is stored.

We agree with the district court's conclusion that expert testimony was required to establish causation. Expert testimony is required when

"the matter to be dealt with is so esoteric that jurors of common knowledge and experience cannot form a valid judgment as to whether the conduct of the parties was reasonable."

Radel v. Bloom Lake Farms, 553 N.W.2d 109, 111 (Minn. App. 1996) (citations omitted), review denied (Minn. Oct. 29, 1996). "Expert opinion is required to prove causation if the issue is outside the realm of common knowledge." Gross v. Victoria Station Farms, Inc., 578 N.W.2d 757, 762 (Minn. 1998). The effect of a corrosive material on the atmosphere above the level where the material is stored is beyond the realm of common knowledge and experience.

We have read the testimony to which Barton directed us and have found no evidence establishing a causal connection between the Trumball cutter stock and the corrosion damage to Barton's tanks. Based on tests that Olson conducted on metal samples from the damaged tanks, he opined that the rust was caused solely by water corrosion. Johnson did not consider himself competent to determine whether water or acid caused the corrosion. No expert testified that a highly acidic material will cause corrosion in the atmosphere above the level where the material is stored. On the contrary, chemist Kari Maas testified that a low pH value does not necessarily mean that a substance will give off corrosive vapors.

Barton argues that such expert testimony was unnecessary because Barton presented evidence that no substance other than the Trumball cutter stock caused the corrosion. First, Barton contends that the visual inspections of tanks eight and nine conducted during the fall of 1995 showed that tanks eight and nine were essentially uncorroded when TexPar began using the Trumball cutter stock and, therefore, the Trumball cutter stock must have caused the corrosion damage. But Sauer conceded that standing on the tank floor and looking up was like "you were in the superdome." Also, Johnson testified that a person must get physically close to corrosion to see it and that it was not possible to adequately inspect a fuel storage tank by standing at the bottom and looking up. Thus, the visual inspections were not sufficient to establish that tanks eight and nine were not corroded when TexPar began using the Trumball cutter stock.

Second, Barton cites evidence that the only materials stored in tanks eight and nine other than the Trumball cutter stock were residual fuel oils. Barton, however, does not cite to evidence that residual fuel oils do not cause corrosion to the atmosphere of steel storage tanks. On the contrary, the evidence indicated that residual fuel oils can cause corrosion in the atmosphere above where the fuel oil is stored. Maas testified that number six fuel oil, when heated, can cause corrosion in the atmosphere at a level above where the product is stored. Johnson testified that the atmosphere areas of 15 to 20-year-old tanks used to store number-six residual fuel oil commonly have corrosion damage.

The district court properly granted JNOV based on Barton's failure to present sufficient evidence to prove causation.

Affirmed.