On October 11, ExxonMobil released its investigative report on the results of soil and sediment tests from Mayflower and Lake Conway. The company submitted the 81-page report to the Arkansas Department of Environmental Quality (ADEQ) as part of its cleanup obligations, and the document is supposed to provide a definitive picture of the environmental situation in the wake of the Pegasus oil spill. ADEQ has been studying the report in the weeks since, and on Monday, it sent a reply to Exxon asking that the oil giant to reevaluate some of its conclusions and continue testing. The agency also forwarded a letter from the Arkansas Game and Fish Commission (AGFC) with more critiques of the report. To assist in conducting an independent evaluation of the data, AGFC hired two environmental consulting companies with a history of investigating oil spills.

Perhaps the most important point in either regulator’s reply is the Game and Fish Commission’s rebuttal of how Exxon’s report treats a class of pollutant called polyaromatic hydrocarbons, or PAHs. Game and Fish says that Exxon’s figure for PAH contamination may misrepresent the amount of toxins still in the environment
These chemicals are found in petroleum and are especially dangerous for two reasons: They’re toxic in low doses, and they don’t easily degrade — that is, they stick around in the environment. As with many complex organic compounds, PAHs come in a great assortment of varieties, each one detectible as a distinct species with its own intimidating name (“Acenaphthene”, “Acenaphthylene”, “Anthracene”, “Benzo(a)Anthracene”, etc). Exxon’s report examines the toxicity effects of 38 separate PAHs, 16 of which are designated as “priority PAHs.” But, says the letter from AGFC to Exxon, that is only about half of the total PAHs present in the source oil. That is, Exxon may have failed to analyze some compounds that should be factored into the overall toxicity picture.


Why? Because the guidelines for PAHs set by the federal EPA were created with waste sites in mind — not oil spills. The EPA test typically looks only for the 16 priority PAHs, because those are the compounds one would find in high quantities at a waste site. Jacqueline Michel, president of one of the consultant firms hired by AGCF, says that a responsible analysis of an oil spill site should examine the effects of all the PAHs in the environment, not just a subset. “Those of us who do oil spill response know that [these] PAHs have the same toxicity mechanisms and are additive,” she explained. (This raises the obvious question: Who knows oil spill response better than Exxon?)

Had AGCF not requested it from the beginning, Exxon may have limited its assessment to the 16 “priority” compounds, rather than 38. But other PAHs in addition to the 38 should have also beeb included, says the letter from AGFC: “The evaluation…is not acceptable in that it analyzes only a subset of PAHs, thereby possibly substantially understating the potential for impacts asserted in ExxonMobil’s report.” Exxon needs to re-anlyze its data, the letter concludes.


AGFC’s other major complaint is that Exxon apparently made no attempt to pinpoint the source of PAHs in its Mayflower samples. Because there are so many different types of these compounds, each petroleum product brings with it a different chemical “fingerprint”: different PAHs at different levels are present in, say, refined motor oil, gasoline, and the Wabasca heavy crude that spilled from the Pegasus. This is important in Lake Conway partly because some background samples referenced in the report show significant petroleum contamination was present in in the lake pre-spill, perhaps from highway runoff or boat traffic. That fact complicates the analysis and muddies the data, but it should be possible for Exxon to ID its oil. Thus, says AGCF, “we request that ExxonMobil conduct fingerprinting analyses to determine which soil and sediment samples are contaminated with the source oil.”

Correspondence from ADEQ points out several other issues with the report. Most importantly, the agency rejects some of Exxon’s recommendations regarding further testing. Exxon concludes that additional sampling in the main body of Lake Conway is not warranted, given the sediment results from the six sites it examined. Since the spill, ADEQ has maintained that there is no evidence any oil ever reached the main body of Lake Conway.


Independent experts consulted by the Times have said the lake likely did escape major contamination, but that reaching a more conclusive answer requires further testing. ADEQ agrees. “ADEQ requests ExxonMobil conduct an additional round of sediment sampling in the main body of Lake Conway (SED-DA -033 through 038) at all depths and full analysis as described in the approved Plan,” says the letter.

Exxon similarly wants to scale back its testing of surface water in the lake and the cove, recommending that it continue taking samples from just two sites on a weekly basis. ADEQ disagrees, saying the company should continue performing water tests at 13 sites.

AGFC has partnered with ADEQ on the Mayflower response since the spill. But though the two state regulators have worked in tandem, their objectives are not identical. While ADEQ is focused on public health issues, AGFC is more concerned with ecology, said Deputy Director Ricky Chastain, who authored the Game and Fish Commission’s letter. “It still is a collaborate effort, but there will be some points where ADEQ will say ‘we’ve reached our goal,’ and AGFC will say ‘we’re not at the point where our goals are reached yet.’”