Interior Secretary Ryan Zinke attends a November event at the Marine Corps War Memorial in Arlington, Va. (Melina Mara/The Washington Post)

Interior Secretary Ryan Zinke’s decision in April to change his travel plans for a fact-finding trip to Channel Islands National Park in California added nearly $2,000 in costs when he left from Santa Barbara, Calif., where his wife owns a second home, according to emails sent among Interior Department officials.

The documents, obtained by the advocacy group Western Values Project under the Freedom of Information Act, show the extent to which National Park Service staff had to rearrange transportation to accommodate Zinke. The two-day trip — which included Zinke’s wife, Lolita, as well as her aunt, Beatrice Walder — was originally scheduled to depart out of Ventura Harbor aboard a Park Service vessel, the Ocean Ranger.

It is unclear what prompted the change in plans for the April 17-18 trip. The Zinkes had just spent the weekend in Santa Barbara and decided to attend an evening town hall event there on the 17th that the conservative group Young America’s Foundation hosted.

Deputy Inspector General Mary Kendall is probing several aspects of Zinke’s travel, including his trips to political gatherings and the extent to which his wife reimbursed the government for costs stemming from her attendance on multiple journeys. In a memo last month, Kendall warned the secretary and his aides that they needed to provide documentation to “distinguish between personal, political and official travel” and that management of his trips had been “deficient.”

Interior press secretary Heather Swift said in an email Monday that the visit “was part of a multi-day visit” to department sites from Sacramento  south to the Channel Islands. Zinke always planned to meet with the team at the national park, “and the office of scheduling reached out to the superintendent’s office as soon as it was clear when he could go.”

For the boat, Swift added, the Zinkes paid via check for her fare and her aunt’s fare. “No costs were incurred due to Mrs. Zinke’s presence.”

Still, the emails chronicle how costs rose after Zinke’s staff stressed he wanted to go in and out of Santa Barbara rather than Ventura.

Russell Galipeau, the Channel Islands superintendent, wrote in an April 7 email that while he was working with National Oceanic and Atmospheric Administration officials to use a vessel it had in Santa Barbara, “I urge against it.” A week later, Galipeau wrote that “to accommodate” Zinke’s request, the crew would need to be paid three hours of overtime each, adding $300, and the government would have to add fuel for an additional eight hours of running time at a price of $1,440. The group ultimately used the Park Service’s boat.

In a phone interview Monday, Western Values Project Executive Director Chris Saeger said the fact that government employees had to go to such lengths and that taxpayers incurred a higher bill suggests a broader problem at Interior. “This pattern of behavior is not just a problem for the people who are making the schedule changes,” he said. “The influence they’re exerting over leadership decisions at Interior is sloppy and ethically deficient.”

Swift countered that Saeger’s group is “a classic dark money group which is run by current and former Democratic Party members and campaign staff.”

Channel Islands National Park is the site of a major restoration effort undertaken by the Nature Conservancy with the Park Service and U.S. Fish and Wildlife Service to bring back native habitat and endemic species such as the island fox, the island scrub-jay and the Santa Catalina Island ironwood. Thousands of sheep, cattle and feral pigs were killed as part of the effort to eliminate invasive species on the network of eight islands.

Zinke was billed $142 on April 25 for the travel costs associated with his wife and her aunt, which grew by mid-June to $152 with late fees. It was paid by the end of June.

The Zinkes were accompanied by Nita Vail, a political supporter of Zinke who had hosted a fundraiser for him in 2014 in Carpinteria, a seaside community about 15 minutes east of Santa Barbara. Vail is a great-granddaughter of the rancher who bought Santa Rosa Island in 1901 and established the Vail & Vickers ranch there. The family, which sold Santa Rosa Island to the federal government for $30 million in 1986, ran cattle on the island until 1998 and operated a commercial hunting business there until 2011.

The National Parks Conservation Association sued in the mid-1990s to end both ranching and big-game hunting on Santa Rosa, arguing that they were degrading crucial habitat. The Vail family closed its hunting business as part of a settlement in that suit.

After touring Santa Rosa with Vail on April 18, Zinke said he would “like to highlight the significant ranching heritage on the island with a working demonstration ranch,” Galipeau said in an email. “At this point it is not clear how this idea will be implemented.”

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