(CNN) — President Joe Biden plans to expand two national monuments in California – one, a mountainous wilderness area east of Los Angeles, and another with tree-covered rolling hillsides north of Napa – in the coming weeks, two sources familiar with the matter told CNN.

Biden will expand the perimeters of the San Gabriel Mountains National Monument by about 110,000 acres and the Berryessa Snow Mountain National Monument by about 13,000 acres, one source told CNN. Both monuments were first designated by former President Barack Obama.

“This is huge, to put it as succinctly and as clearly as I can,” Democratic Sen. Alex Padilla of California, a longtime advocate for expanding both monuments, told CNN.

The exact timing of an expansion declaration is unclear, but it is likely in the coming weeks – and could coincide with Earth Day, the sources said.

A White House spokesperson declined to comment. The Washington Post first reported the monument expansions.

National monuments are areas of historic, cultural or natural significance that are designated for federal protection. The redrawn boundaries for the California monuments will serve several purposes, including protecting sacred sites for Native American tribes, conserving land and expanding public access to the outdoors.

“The San Gabriel Mountains are among the most pristine and beautiful public lands in the country, with more visitors annually than Yellowstone, and they are right next to one of the nation’s densest and most park-deprived population centers,” Rep. Judy Chu, a Democrat from California, said in a statement. “I’d be absolutely elated for President Biden to use his executive authorities to finalize this, recognize the significance of all these lands, and unlock additional federal supports and resources.”

During the first three years of his term, Biden has conserved more than 24 million acres of public lands, most recently designating a new national monument near the Grand Canyon – the Baaj Nwaavjo I’tah Kukveni National Monument. Biden has also designated new monuments in Nevada and Colorado, and restored protections for national monuments in Utah that were restricted by former President Donald Trump.

Padilla said he applauded the Biden administration for “utilizing every tool in the toolbox, working with Congress when he can and using his executive authority when he needs to.”

White House senior adviser for international climate policy John Podesta nodded to future conservation announcements from the Biden administration at a Thursday event at the Washington Post.

“I worked for President Clinton, for President Obama. They both had tremendous conservation records,” Podesta said. “President Biden is just surpassing that in terms of what he’s able to do in the first term. And I think we’ve got more to come, including better use and better protection of public lands.”

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