When Chelsea Benally worked in a confidential government research program, she never knew exactly what she was building.

Her commissions were high security government assignments and she wasn't supposed to ask questions.

Years later, Benally knows exactly the purpose of her research and can talk about it freely.

The first Indigenous woman to graduate from the University of Alberta with an engineering PhD, Benally is working on new ways to treat tailings water, a toxic byproduct in the process of extracting bitumen from oilsands.

Benally — a member of the Navajo Nation who hails from Flagstaff, Ariz., — said working in remediation has been a passion since grade school when she first learned about environmental decline and the engineers who wanted to "fix things."

But before she would have a hand in oilsands reclamation, Benally spent years working in a government lab.

You're only given the information that you need to know. -Chelsea Benally

After studying chemical and environmental engineering at the University of Arizona, Benally's first job in engineering was at Sandia National Laboratories, a national security technology company in Albuquerque, N.M.

As a government contractor, Sandia produces nuclear weapons and other engineering commissions for the government.

It was a good gig for the junior-level chemical engineer. The work was secure, well-paying and she was even sent by the company to university to complete her master's degree.

But Benally found the work unfulfilling, she said.

"You're not supposed to ask, 'What is this component or where does it go?' You're not supposed to ask what they're going to be used for," she said in an interview Monday with CBC Radio's Edmonton AM.

"You're only given the information that you need to know."

Her work had to be kept confidential and her training included warnings against espionage.

"If you're ever travelling for international work, you have to be careful if people ask you questions, what information you share and where you leave your things," she said.

"Even when I was working there later on, it didn't feel like I knew anything that anybody would want to gain knowledge about."

Time for change

When Benally was accepted into a high-level training course on nuclear weapons technology, she decided it was time to step back and do something "more useful."

"Before I started I thought, if I'm going to leave, I should leave now because if I go through this and learn all these things, I don't know if they'll just let you leave."

I didn't really think about being the only one. - Chelsea Benally

After learning of the University of Alberta's oilsands remediation work, Benally applied and was accepted in 2011.

She and her young son moved to Alberta, where she began working on her doctorate, studying the treatment of tailings water under researcher Mohamed Gamal El-Din.

Her work thus far has focused on creating membranes and other absorption materials that can filter toxins from water.

Knowing that she can use her education to work on problems created by humans is rewarding Benally said, but she remains humble about her work.

"I'm just working on a very small piece."

Being the first Indigenous woman to graduate with a PhD from the University of Alberta's Faculty of Engineering is bittersweet for Benally.

She didn't know about the honour until last spring. She wishes there was more Indigenous women represented in engineering.

"I didn't really think about being the only one," she said. "A lot of the people who are in my classes are actually from different countries. I didn't feel out of place.

"I feel sad in a way because although I'm Indigenous, I'm not from Canada. In some ways, I feel sad that it's not someone from this country. I wish there were more."