After years of meetings in D.C. conference rooms, a seven-year partnership and about $12 million in effort, the Cemex bill — the city of Santa Clarita’s last hope for stopping a 56 million-ton sand-and-gravel mine from opening next door — is in jeopardy due to a New Mexico senator’s legislative hold, officials said Saturday.

Congressman Buck McKeon, R-Santa Clarita, pulled HR 5472, commonly known around Santa Clarita Valley as “the Cemex bill,” off the suspension calendar and passed it as a stand-alone bill with a voice vote of the waning moments of the House’s 113th legislative session Thursday.

The move was accomplished less than a month after Sen. Barbara Boxer introduced a bill with identical language, having learned from the Congressional Budget Office the bill achieved a zero score, meaning no cost to the taxpayer.

Related: BREAKING: House Passes McKeon Cemex Bill To Stop Mine

The bill’s progress came from more than two decades of discussion, springing from a once-contentious relationship with an international mining company that became a partnership as Cemex has waited years for compensation for its Soledad Canyon mineral rights.

However, the 11th-hour vote in the House means the Soledad Canyon Settlement Act — which is its moniker in the Senate — must garner support from all 100 senators.

After years of meetings in D.C. conference rooms, a seven-year partnership and about $12 million in lobbying efforts, the city of Santa Clarita’s hopes of stopping a 56 million-ton sand-and-gravel mine from opening next door are in jeopardy due to a New Mexico senator’s legislative hold, officials said Saturday. Photo courtesy of SCVnews.com

Sen. Martin Heinrich, D-N.M., has placed a hold on the bill, according to sources, an indication he won’t support the bill.

It’s crucial opposition at this point, with a source close to Boxer’s office reporting the deadline is, in all likelihood, Monday.

It might not only be the city’s last chance for the bill — it might be the last chance to compensate Cemex for its mining contracts without forever transforming land next to a national monument, officials said.

Soledad Canyon Settlement Act, aka the Cemex bill

The Soledad Canyon Settlement Act, aka the Cemex bill or S.B 2938, calls for Cemex to cancel two 10-year mining contracts on land owned by the city less than a mile east of Agua Dulce Canyon Road.

In exchange, the Bureau of Land Management would sell 10,000 acres in San Bernardino County, with the proceeds going to Cemex as compensation for their contracts.

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 sale, reportedly is where the concern lies.

Initially, BLM officials expressed opposition to the bill last year, in testimony in front of a Senate panel.

The city has worked hard, unsuccessfully, to reverse the agency’s position in light of several recent developments, according to Mike Murphy, city of Santa Clarita intergovernmental relations officer.

By executive order, President Barack Obama declared 346,000 acres of national forest land in the San Gabriel Mountains the nation’s newest national monument in October, a plot that abuts land the city is trying to avoid turning into a gigantic gravel pit.

Because the monument land is adjacent to the property Cemex has mineral rights for, Santa Clarita City Council members authorized the transfer of the land to the federal government conditional upon the passage of the legislation.

Bob Kellar testifies in front of a Senate committee on the importance of Cemex

City and federal officials have identified the land as an ideal northern corridor to the monument, Murphy said.

All Santa Clarita officials can do now, Murphy said, is hope Heinrich — who applauded the passage of a historic public lands package Friday in the National Defense Authorization Act that contained dozens of bills similar in nature to Cemex’ — changes his mind.

City officials are encouraging concerned parties, including Santa Clarita Valley residents and neighbors of the affected area to contact Sen. Martin Heinrich: at his website, www.heinrich.senate.gov; @MartinHeinrich on Twitter; on Facebook; or at  (202) 224-5521 (office); (202) 228-2841 (fax).

Officials said Monday, December 15, 2014, is the deadline for the vote