President Barack Obama’s declaration Friday of the San Gabriel Mountains as a national monument bolsters Santa Clarita’s argument against 100-plus years of Cemex mining in the Santa Clarita Valley, officials said Wednesday.

“The national monument designation does not alter the contracts that Cemex holds with the Bureau of Land Management,” said Mike Murphy, intergovernmental relations officer for Santa Clarita.

However, it does support what Santa Clarita city officials, and its supporters in the effort, have been saying all along, he said.

“It’s an additional affirmation of the importance of the ecological resources in that area, and that’s part of the argument that we’ve been making with the Department of the Interior and with Congress,” Murphy said. “There are significant ecological natural resources in that Upper Santa Clara River area that are incompatible with a large-scale mining operations.”

The land Cemex has contractual mining rights for abuts a corner of the new national monument, according to maps provided by Santa Clarita officials, who have testified in front of Congress about the land.

A map of the eastern portion of the Santa Clarita Valley showing where the San Gabriel Mountains monument will go, and the land where Cemex currently holds mining rights

“(The declaration of a monument) doesn’t take away from our commitment to operate as a responsible corporate neighbor, and we’ll take the necessary steps to make sure that we do that,” said Sara Engdahl, a CemexUSA spokeswoman.

Cemex remains committed to working with the city on S.B. 771, she added.

Related: Santa Clarita Mining Could Be Issue For 50 Years If Cemex Bill Fails

Obama’s declaration Friday was the culmination of a legislative effort started by a neighboring district supported by Santa Clarita Valley officials.

Using the Antiquity Act of 1906, Obama declared roughly 346,000 acres the San Gabriel Mountains National Monument, including 14,700 acres of the 25th Congressional District, east of Highway 14 in Canyon County/Soledad Canyon and the region south of Acton.

“Over 15 million people live within 90 minutes of the San Gabriel Mountains,” Obama said last week. “These mountains provide residents with roughly 30 percent of their water and 70 percent of their open space.”

The area is being closely watched by Santa Clarita officials who have been working cooperatively with Cemex for several years to prevent a massive mining operation from moving to the east side of the Santa Clarita Valley.

Related: Senator Boxer Brings Back Cemex Bill To Stop Mining

Cemex owns two mining contracts for Soledad Canyon, each 10 years in length, which would yield about 56 million tons of usable aggregate — a total of 78 million tons of the material used to make gravel and concrete — over the next 20 years. But the mining of the sand and gravel is expected to be necessary for much longer than that, according to Bureau of Land Management officials.

The potential value of the aggregate and the contracts are significant because Cemex is currently agreeable to a land-swap deal proposed by Sen. Barbara Boxer, D-Calif., who has proposed legislation offering land in San Bernardino County in exchange for Cemex forfeiting its mining rights in that area.

The latest product of the cooperative effort, S.B. 771, calls for BLM land in Victorville to be sold, with those proceeds compensating Cemex for the value of the contract. The land would also be made unavailable for future mining.

However, the deal must “zero out,” meaning the potential value of the mining contracts the federal government would receive from royalties must match the value in the land it would be giving up, officials said.

The Congressional Budget Office has released no update on its valuation for the bill, and city officials have not been given specifics on how the land values and potential royalties are going to be projected.

Local officials have received indications from Boxer’s office there is a “significant” difference in how the two sides feel the value should be calculated, Murphy said. One example he gave was that BLM officials anticipate a value of $1.50 per ton in royalties after the first four years (when it’s guaranteed to have a value of $0.50 per ton), whereas local officials feel that’s unrealistic and the ramp-up would likely occur more gradually.

Cemex officials have said if something doesn’t happen in the current congressional session, which ends in December, then it eventually will look into capitalizing on their mining contracts.

A Cemex officials did not return a call seeking comment for this story.

Cemex mining in Santa Clarita

In the meantime, Cemex remains a partner in the effort to move the potential mining site out of the Santa Clarita Valley, city officials said. It’s too early to look down the road of what-ifs because the legislative session isn’t over, yet.

“This designation doesn’t change anything that’s already in place,” Murphy said, “it just adds an additional argument to the argument we’ve been making for some time — of the incompatibility of the mine with the ecological resources in the Upper Santa Clara River.”

The area faces a need for aggregate and a potential supply shortage if the land-swap deal is approved, BLM officials have said.

The canyon has the potential to produce 356 million tons of sand and gravel, and it’s not clear if Friday’s declaration could impact that potential, but it means the massive sand-and-gravel mine would neighbor a national monument if the land-swap legislation is rejected.

The impetus for Friday’s move came from Rep. Judy Chu, D-Pasadena and H.R. 4858, the San Gabriel National Recreation Area bill, Murphy said.

While the bill ultimately failed to gain the necessary traction, it led to talks between Chu’s office and the White House, which saw the importance of the area as an ecological resource, Obama said Friday.

“Let me once again say ‘thank you’ to all of you who made this happen, and for your continued commitment to preserving our magnificent natural inheritance, and for ensuring that this ‘geography of hope’ remains the birthright of all Americans,” Obama said in his closing remarks, “not only for today, but for generations to come.”