The Center for Biological Diversity is threatening to sue the Environmental Protection Agency (EPA) over its decision earlier this year to exempt portions of the Arroyo Grande Oil Field from the Safe Drinking Water Act.

Maya Golden-Krasner, the center's climate deputy director and senior attorney, said that the federal agency didn't complete its due diligence before issuing a decision in April, violating both the Endangered Species Act and the National Environmental Protection Act.

"This is a federal agency that's approving it, and they're supposed to consider the foreseeable direct and indirect consequences of their decisionmaking," Golden-Krasner said. "The law requires agencies to consider those consequences."

Although the decision didn't pertain to specific projects that would disturb endangered species habitat, it could potentially lead to expanding drilling on the the oil-producing site that overlies the field on both sides of Price Canyon Road near Pismo Beach.

Sentinel Peak Resources, the site's operator, put a project on hold while it awaited the decision. In a previous interview, Sentinel Peak spokesperson Christine Halley indicated that the oil company was considering whether to pursue drilling the 31 oil wells left on a 95- well project already approved by the county.

Freeport-McMoRan applied for an aquifer exemption in the field during 2014 after the California Department of Conservation discovered there were permitted injection/re-injection wells being drilled into parts of the aquifer that were considered to hold safe drinking water. In the EPA's April decision, it stated that the application, which had since been taken over by Sentinel Peak Resources, demonstrated that the oil field didn't currently serve as a source of drinking water and wouldn't in the future.

New Times reached out to Sentinel Peak Resources for comment and was referred to the California Independent Petroleum Association.

"After a rigorous review process that included four state agencies and the federal EPA, months of scientific study, and numerous public meetings, regulators agree that the oilbearing formation has no impact to the region's drinking water," association CEO Rock Zierman said in an emailed statement. "[Center for Biological Diversity] has already had a previous lawsuit on this issue dismissed by the courts, and they're filing another frivolous lawsuit that seeks to threaten the state's energy security."

The center filed a lawsuit in 2016 that was designed to slow the approval process on the aquifer exemption and force the state Division of Oil, Gas, and Geothermal Resources and the state Water Resources Control Board to conduct more environmental reviews of the aquifer.

In the 60-day notice of intent to sue sent to EPA Administrator Andrew Wheeler on July 25, 2019, the center stated that a federally listed endangered species of particular concern is a flower called the Pismo clarkia, which the U.S. Fish and Wildlife Service considers to be a priority to recover. Golden-Krasner said the flower has fragmented habitats in a tiny area that overlaps with the field.

Even without construction of new oil wells, Golden-Krasner said, it could mean that Sentinel Peak reworks the wastewater injection wells that are currently on its site, expanding their capacity, which could disturb the land above the aquifer.

"It's a foreseeable result," she said. "They didn't do any environmental review."

Although the EPA has granted other aquifer exemptions in the state of California, Golden-Krasner said the center hasn't filed or threatened to file a lawsuit in any of those cases. The Arroyo Grande Oil Field was of particular concern, she said, because of the people who depend on groundwater supplies adjacent to the field and the potential for expansion of oil production.

"We probably could have filed similar cases for the other ones, but because this one has specific concerns, we want to support the community that lives around the oil field," Golden-Krasner said. "Winning this case would set a precedent for all of the others."