Industrial plant at night

Two expert witnesses, one for a coal-fired power plant and one for the people who allege that it polluted the surrounding area, will be allowed to testify about their air modeling reports, a federal judge has ruled.

Three related cases were consolidated for discovery after dozens of people who live near the Bruce Mansfield Power Plant in Shippingport, Pa., filed suit against the plant when white and black rain fell on the area, allegedly causing property damage and health problems.

“Two of the key issues in these cases are the extent of the area affected by the white rain and the two black rain events and the amount of material deposited by those events,” said U.S. District Chief Judge Joy Flowers Conti of the Western District of Pennsylvania in Hartle v. FirstEnergy Generation. “The parties seek to introduce air modeling experts to opine about these issues,” she said.

FirstEnergy Generation owns the Bruce Mansfield plant and the lead plaintiffs in the other two cases are David and Rikki Patrick and Robert and Carol Price.

The two experts each used a different model as a method for assessing the level and range of pollutants contributed by the plant to the white rain. Each side argued that the other’s expert used the wrong model.

The judge held that neither model is perfect, but that doesn’t preclude either expert from testifying.

“Which of the competing models better reflects the facts of these cases is a matter for the jury to decide,” Conti said.

The third expert witness, who had been offered by the plaintiffs and was challenged by the power plant, will be excluded from testifying, though.

Nicholas Cheremisinoff, a chemical engineer with expertise in fluid dynamics, didn’t do his own air modeling but, rather, reviewed the reports submitted by Ronald Petersen, the plaintiffs’ main expert, and Peter J. Drivas, the defendant’s expert.

“Cheremisinoff’s evaluation of Petersen’s white rain opinions amounts to vouching for Petersen and is cumulative to Petersen’s testimony. Cheremisinoff is not an air modeler,” Conti said.

“Because Cheremisinoff’s opinions are unnecessarily cumulative and would not help the trier of fact, defendant’s motions to preclude his expert testimony will be granted,” the judge ruled.

Both Petersen and Drivas will be allowed to testify, though.

Petersen, for the plaintiffs, used a model called AERMOD to examine the range of the white rain. That model is preferred by the U.S. Environmental Protection Agency for regulatory air dispersion modeling, Conti said.

“To predict white rain deposition, Petersen entered inputs for emission rates, droplet size, stack flow rate and temperature, and meteorological conditions,” according to the opinion. “Petersen ran the model under three different operating scenarios to reflect changes to the plant over time. For each of the three scenarios, Petersen produced maps with contour lines outlining areas where white rain was deposited at a given level. Petersen mapped deposition for several time periods: total annual deposition, maximum 24-hour deposition, and maximum one-hour deposition.”

However, the power plant’s expert, Drivas, argued that AERMOD is the wrong model to use in this case because it is meant for dry particulates gases and doesn’t take into account the evaporation for the wet droplets in this case.

Petersen made some adjustments to the model to account for evaporation, which the judge found to be satisfactory.

“While defendant may quarrel with the accuracy of Petersen’s handling of evaporation, this goes to credibility or weight, not admissibility,” Conti said.

Drivas, on the other hand, used a model called AGDISP that was made to model airborne spray pesticides, according to the opinion.

“Using AGDISP, Drivas calculated that over 95 percent of water droplets released from the Bruce Mansfield stacks will evaporate in the air and that almost all droplet deposition occurs within 1,500 feet of the stack,” Conti said. “At a distance of one-half mile from the stacks, less than 2 percent of released water droplets remain aloft. AGDISP predicted that these remaining droplets evaporate in less than 10 seconds, leading to no deposition beyond one-half mile from the stacks.”

The plaintiffs discredit Drivas’ use of the AGDISP model by arguing that it isn’t a reliable method for measuring raindrops and that the EPA recommends the AERMOD model for predicting dispersion of air and pollution from power plants, according to the opinion.

“Since these cases do not directly involve regulatory action and since AERMOD is less appropriate for measuring wet droplets than criteria air pollutants, the EPA guideline does not justify the exclusion of AGDISP as scientifically unreliable,” Conti said.

Neither method is perfect in this situation, Conti held, saying that it isn’t up to the court to decide which is superior.

Saranac Hale Spencer can be contacted at 215-557-2449 or Follow her on Twitter @SSpencerTLI.

(Copies of the 23-page opinion in Hartle v. FirstEnergy Generation, PICS No. 14-0409, are available from The Legal Intelligencer. Please call the Pennsylvania Instant Case Service at 800-276-PICS to order or for information.)