Congressman Raúl Grijalva will announce a bill this afternoon designed to permanently ban uranium mining in the Grand Canyon watershed.

The Tucson legislator's measure, officially called the Greater Grand Canyon Heritage National Monument Act, calls for protecting the area by declaring the region a national monument.

According to a statement from Grijalva's office, the bill, if successful,"permanently protects the Grand Canyon from new uranium mining claims; protects tribal sacred cultural sites; promotes a more collaborative regional approach between tribal nations and federal land managers; protects commercial and recreational hunting; preserves grazing and water rights; and conserves the Grand Canyon watershed."

Leaders of the Havasupai, Hualapai, Navajo, and Hopi tribes are scheduled to join Grijalva this afternoon in Flagstaff to show their support for the measure and to speak about the cultural and ecological significance of the area.

This new bill from Grijalva represents his latest effort in the long war he's been waging against uranium mining: "Mining so close to the Canyon could seriously impair the region’s ecosystems: wreaking havoc on the landscape, drying up critical seeps and springs, disturbing fish and wildlife, and releasing toxic chemicals into the environment," he wrote in a letter to former U.S. Interior Secretary Ken Salazar about the practice.

"With mining claims positioned so close to the Canyon and the Colorado River, a range of contaminants from heavy metals to uranium could also degrade the downstream water supply, impacting a water supply relied on by millions of Americans. Not to mention the fact that uranium mining produces permanent radioactive waste, an environmental toxin which must disposed of in an urgent, safe manner."

Grijalva, a pro-environment, liberal Democrat — he was the first in Congress to endorse Senator Bernie Sanders for president — has worked with environmental groups and tribal leaders to get the watershed national monument status and to protect other culturally and ecological significant lands.

It's been an uphill battle, both legislatively and in the courts, as his stance on the issues is particularly controversial in a state known for allowing the environment to take a backseat to industry.

He was a strong supporter and advocate of the Obama administration's proposal to place a 20-year moratorium on new uranium mine claims in the Grand Canyon watershed, which passed in 2012, and earlier this year, introduced legislation reforming the 1872 Mining Law.

Also earlier this year, Arizona Congressman Paul Gosar spearheaded a bill passed by the House that seeks to block the Grand Canyon watershed from being declared a national monument.

“A unilateral declaration of the nearly two million acres in the Grand Canyon Watershed as a National Monument would stifle development, kill jobs and erode the extensive cooperation and success that federal and state agencies in Arizona have achieved to date. The Antiquities Act has been significantly abused by this rogue president and today the House took bold action to prevent future executive land grabs throughout the country,” Gosar said in a statement.

But Grijalva, backed by environmental and tribal groups around the country, has declared he will not give up the fight.

