Results from an anonymous survey of the department's nearly 70,000 employees show that 8 percent reported being victims of sexual harassment and 16 percent reported harassment based on gender. More than 9 percent described harassment based on race or ethnicity.
About 450 employees experienced some form of sexual assault, including unwanted touching, forced sex or attempted sex, according to the report.
The Bureau of Indian Affairs and National Park Service reported the most incidents, with 40 percent of BIA workers and 39 percent of parks workers reporting some form of harassment.
The survey was conducted from January to March 2017 and covered the 12-month period before the survey was completed. More than 28,000 employees participated.
Interior Secretary Ryan Zinke released the National Park Service figures two months ago at a Grand Canyon news conference intended to highlight widespread complaints of harassment and workplace discrimination within the agency.
Federal investigators have uncovered problems at many of the nation's premier parks, including Yosemite, Yellowstone, and Canaveral National Seashore in Florida. A sexual harassment scandal at the Grand Canyon forced the retirement of the park superintendent in May 2016.
The former Yosemite superintendent retired last year after allegations that he created a toxic work environment surfaced at a congressional hearing. Don Neubacher headed the California park for nearly seven years and spent 37 years with the park service. Yosemite is one of the nation's oldest and most popular national parks, drawing more than 4 million visitors a year.
Zinke said in a statement Thursday he has "zero tolerance for any type of workplace harassment," adding that he has directed department leaders to move quickly "to improve accountability and transparency with regard to this absolutely intolerable behavior."
A spokeswoman declined to provide specific examples of supervisors or other employees who were fired, citing personnel rules.
"Generally speaking, those terminated abused their authority" by intimidating or harassing fellow employees, spokeswoman Heather Swift said. "This includes but is not limited to sexual harassment."
Two firings based on misconduct were previously made public: Former Canaveral Chief Ranger Edwin Correa, who made unwanted sexual advances to subordinates, and former Bureau of Land Management Supervisory Agent Daniel Love, for misusing his position to benefit himself and family.
Underscoring what some have described as a culture of tolerance for harassment, less than 36 percent of employees who filed a complaint or grievance report and participated in the survey said action had been taken in response to their complaints.
By comparison, 39 percent said they'd been encouraged to drop the issue and 29 percent who formally complained about harassment said they were punished by agency leaders for bringing up the issue.
Those findings "suggest there was a meltdown of the accountability mechanisms" at the department, said Jeff Ruch with Public Employees for Environmental Responsibility, an advocacy group for government employees that's been critical of Zinke's handling of harassment.
"The same people are there. I don't know about these people that they fired. There's no evidence of it" other than Love and Correa, Ruch said.
While the National Park Service stood out in terms of sheer numbers in the new survey - an estimated 7,200 employees harassed in the previous year- high rates of harassment were seen across the agency.
Thirty-five percent of workers at the Bureau of Land Management and 31 percent at the Fish and Wildlife Service reported some form of harassment.
Brown reported from Billings, Montana.
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