Members of the Senate Judiciary Committee filed dozens of amendments to a bipartisan immigration reform bill that is set to undergo markups on Thursday.

The amendments seek to do a wide range of things, from barring the creation of a border-crossing fee to making foreign worker provisions more market-based and even collecting DNA samples from immigrants seeking legal status.

Many of them, however, address tightening border security, a move that Republican senators have said is critical if the bill – introduced last month by four Democratic and four Republican senators – is to have a real chance of being passed.

The bipartisan bill, called the Border Security, Economic Opportunity, and Immigration Modernization Act, basically seeks to make enforcement stricter while also providing an opportunity for undocumented immigrants to obtain legal status.

U.S. Sen. Orrin Hatch, R-Utah, filed 24 amendments.

“These amendments are reasonable, common-sense fixes to the bill that ensures taxpayers are protected and that our economy has access to the workers it needs to compete in a global economy,” Hatch said in a press release. “I appreciate the hard work my colleagues have done in putting this complicated bill together, and I look forward to working with them to implement these needed changes to the bill moving forward.”

One of the legislation's authors, Sen. Marco Rubio, R-Fla., has already acknowledged that the bill will face a tough road to passage if the border security elements are not improved.

Rubio issued a press release thanking colleagues who had filed amendments.

“Throughout this next phase of the immigration debate, we want to continue hearing from the public about how to get immigration reform right,” Rubio said in the statement. “For members of the Senate Judiciary Committee, this is their first chance to make a good-faith effort to improve the bill. I look forward to working with them throughout this process to ultimately fix our broken immigration system and ensure we never repeat today’s broken mess again.”

Senate Judiciary Committee Chairman Patrick Leady, D-Vt., filed amendments calling for the elimination of a border crossing fee proposal that had elicited an outcry from communities along the Southern and Northern borders. Many business owners in U.S. border towns expressed concerns that the fees would discourage people from crossing and would hurt the local economies.

He also wants to see gay and lesbian partners and families included in immigration reform laws.

Hatch’s amendments include tightening law enforcement aspects of the bipartisan bill, expanding the collection of back taxes for people who obtain legal status, and collecting DNA samples from immigrants who would seek legal status offered by the reform bill.

Republicans in the House have warned that immigration reform may face a tougher fight in their chamber. Some Republicans have introduced piecemeal bills, preferring that approach to one massive measure.

Echoing concerns raised by a number of Republicans, Rep. Rand Paul of Kentucky said that the bill relies too much on setting goals and requiring studies about border security, instead of insisting on actual accomplishments. Under the bill, "You have to have a plan to build a fence, but you don't have to build a fence," he complained.

The bill allocates $5.5 billion for border measures aimed at achieving 100 percent surveillance of the entire border and blocking 90 percent of border crossers and would-be crossers in high-entrance areas.

The Homeland Security Department would have six months to create a new border security plan to achieve the 90 percent effectiveness rate. Also within six months, the department would have to create a plan to identify where new fencing is needed. Once that happens, people living here illegally could begin to apply for a provisional legal status.

If the 90 percent rate isn't achieved within five years, a commission made of border state officials would make recommendations on how to do it.

After 10 years, people with provisional legal status could apply for permanent residency if the new security and fencing plans are operating, a new mandatory employment verification system is in place, and a new electronic exit system is tracking who leaves the country.

Among other things, Rubio has discussed strengthening the "triggers" that require certain steps to be taken before a path to citizenship can begin.

Officials with the Department of Homeland Security testified before a Senate Tuesday that the U.S.-Mexico border is more secure than ever but they said the provisions in the bill would help them make it even stronger. They praised the pending legislation for directing more resources to the agency for surveillance equipment and for authorizing 3,500 new Border Patrol officers.

The hearing touched briefly on the Boston Marathon bombings, which exposed some failures, including an apparent lack of communication among federal agencies when one of the alleged bombers, Tamerlan Tsarnaev, traveled to Russia last year. A student from Kazakhstan accused of hiding evidence for one of the bombers also was allowed to return to the U.S. in January without a valid student visa.

Sen. John McCain, R-Ariz., an author of the immigration bill, said the legislation could be amended to address any such problems. "There are some obvious areas on student visas and humanitarian visas that need to be looked at," he said.

The Associated Press contributed to this story.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino

Elizabeth Llorente can be reached at elizabeth.llorente@foxnewslatino.com

Follow Elizabeth Llorente on https://twitter.com/Liz_Llorente

Like us on Facebook
Follow us on Twitter& Instagram