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With the government on the brink of a shutdown as Congress remains at an impasse on a funding deal, federal departments and agencies have begun the mandatory process of planning to bring nonessential functions to a halt at the start of the new fiscal year on October 1.

The Office of Management and Budget reminded senior agency officials last week to update and review shutdown plans.

Every department and agency has its own set of plans and procedures. That guidance includes information on how many employees would get furloughed, which employees are essential and would work without pay, how long it would take to wind down operations in the hours before a shutdown, and which activities would come to a halt. Those plans can vary from shutdown to shutdown.

Should Congress fail to pass a short-term spending bill to keep the proverbial lights on, a shutdown could have enormous impacts on all Americans, in areas from air travel to clean drinking water.

The nearly 2.2 million Americans who are federal employees – plus the 1.3 million active-duty troops – would feel the effect immediately if their agencies aren’t funded. Essential workers would remain on the job, but others would be furloughed until the shutdown is over. None would be paid during the impasse.

For many of them, a shutdown would strain their finances, as it did during the record 35-day funding lapse in 2018-2019.

“We had thousands of members across the country who returned holiday presents because they needed the cash, missed a mortgage payment, took out short-term loans and ran up their credit card debt because they had no paychecks for a month,” said Doreen Greenwald, president of the National Treasury Employees Union, which represents 150,000 workers in 35 agencies. “They stood in line at food banks, pulled their children from child care, were unable to put gas in their cars and begged creditors for grace. This is not how the United States of America should treat its own employees.”

On average, members of the American Federation of Government Employees earn between $55,000 and $65,000 a year, while hourly workers earn an average of $45,000 annually. But thousands make closer to $15 an hour, or $31,200 a year.

“Most of our members live paycheck to paycheck and can’t afford to miss one payday, let alone more,” said Everett Kelley, president of the union. “That’s why we are calling on Congress to do its job and pass a budget to prevent a government-wide shutdown.”

The American Federation of Government Employees is the largest federal employee union with 750,000 members in nearly every agency of the federal and Washington, DC, governments. Its members include health care professionals, correctional and law enforcement officers, park rangers, Transportation Security Administration agents and Social Security workers.

But certain functions would continue even if the government shuts down. Social Security payments to senior citizens, people with disabilities and others would still be distributed, as would pension benefits to retired federal workers and military personnel. Medicare and Medicaid benefits would not be affected.

Here are some of those impacts that Americans can expect:

Travel

The White House is sounding alarms about massive disruptions to air travel as tens of thousands of air traffic controllers and Transportation Security Administration personnel work without pay. During the 2019 shutdown, hundreds of TSA officers called out from work – many of them to find other ways to make money.

The White House warned that a shutdown could risk “significant delays for travelers” across the country.

“During an Extreme Republican Shutdown, more than 13,000 air traffic controllers and 50,000 Transportation Security Officers – in addition to thousands of other Federal Aviation Administration (FAA) and Transportation Security Administration (TSA) personnel – would have to show up to do their critical jobs without getting paid until funding becomes available,” a White House news release said.

It added, “In previous shutdowns, this led to significant delays and longer wait times for travelers at airports across the country.”

The White House also noted that a shutdown “would halt air traffic controller training—potentially leading to long-term disruptions to the industry at a moment when we’ve seen critical progress filling a backlog of controllers.”

The news release also offered a state-by-state breakdown of TSA officers and air traffic controllers to showcase some of the local impacts. Notably, Florida has 6,108 TSA officers and 1,157 air traffic controllers. California has 5,469 TSA officers and 1,418 air traffic controllers.

And some passport facilities could close in the event of a shutdown, the State Department’s 2022 guidance states.

National security

The White House has also warned of shutdown impacts to national security, including the 1.3 million active-duty troops who would not get paid during a shutdown.

“Extreme House Republicans are playing partisan games with peoples’ lives and marching our country toward a government shutdown that would have damaging impacts across the country – including undermining our national security and forcing service members across the country and around the world to work without pay,” the White House said in a fact sheet shared with reporters.

Service members, who are essential federal employees, would receive their paychecks after the conclusion of a shutdown.

The White House also warns that the furlough of civilian Defense Department colleagues would leave the US vulnerable.

“Hundreds of thousands of their civilian colleagues in the Department of Defense would also be furloughed, affecting the ways in which the Department manages its affairs globally, including the vital task of recruiting new members of the military. All of this would prove disruptive to our national security,” the White House’s messaging said.

In an effort to bring the messaging home, the White House also offered a breakdown of the active duty troops in each state, previewing the local economic impacts for thousands of Americans working without pay. While 171,700 troops live abroad, a shutdown would impact 163,300 troops in California, 129,400 in Virginia, 114,200 troops living in Texas, and 95,900 in North Carolina.

In three recent shutdowns that lasted at least two weeks, members of the military were paid – either because Congress had passed the necessary appropriation or because lawmakers approved legislation guaranteeing service members’ pay, said Andrew Lautz, senior policy analyst at the Bipartisan Policy Center.

The Internal Revenue Service

The shutdown would have a big impact on the Internal Revenue Service and its ability to service taxpayers, according to the contingency plan that the Treasury Department released on Thursday.

Most core tax administration functions would stop, and about two-thirds of IRS employees – about 60,000 people – would be furloughed.

The agency would not process refunds, except in cases where e-filed, error-free refunds could be direct-deposited automatically.

It would be much harder for taxpayers to get through to the agency. Phone calls would go unanswered, Taxpayer Assistance Centers would close and the IRS would not respond to paper correspondence.

The agency typically receives 46,000 calls a day and the 363 assistance centers provide service to about 5,000 people daily during the month of October, according to a Treasury email outlining the impacts. It would also take longer for people who mail in correspondence to get responses after the agency reopens because of the backlog.

“It will be incredibly difficult for Americans to conduct business with the IRS during the impending government shutdown,” Greenwald said.

More Americans than usual have an October filing deadline this year. In addition to those who requested extensions, many folks in California and some in other states received more time to file their taxes because of natural disasters. There are 10.5 million individual 1040 filers on extension through the October 16 deadline, the Treasury Department said.

However, the IRS would be able to continue some functions that are funded with the boost it received from the Inflation Reduction Act. It would keep preparing for the upcoming filing season – updating tax forms and technology system and hiring and training staff. And it would continue limited modernization efforts and provide income verification to mortgage lenders, banks and others through its Income Verification Express Service.

The 30,000 employees who would remain on the job would be paid through the Inflation Reduction Act funds, Greenwald said.

The 2018-19 shutdown, which happened just before the start of the filing season, also wreaked havoc on the agency. Fewer phone calls were answered, hold times were longer and the backlog of correspondence ballooned, according to the National Taxpayer Advocate’s annual report in 2019.

The economy

There could also be massive economic implications. In the event of a shutdown, the Bureau of Labor Statistics says it will stop releasing data, including key figures on inflation and unemployment. A lack of crucial government data would make it difficult for investors and the Federal Reserve to interpret the US economy.

The Small Business Administration would not provide new loans to any businesses.

“Each weekday the government is shut down, hundreds of small businesses would see their 7(a) and 504 loan applications fail to move forward,” a White House news release said, noting that a shutdown “would deny more than $100 million in critical financing to American small businesses every day.”

Public health and safety

There would be impacts to public health and safety across a variety of agencies should the government shut down.

While emergency public health measures, outbreak response and laboratory functions will remain in place, the US Centers for Disease Control and Prevention warns that “other public health activities will be functioning at a reduced capacity.”

The Food and Drug Administration, the White House warns, “could be forced to delay food safety inspections for a wide variety of products all across the country.”

And the Occupational Safety and Health Administration “would be forced to limit workplace inspections,” the White House warns, putting worker safety at risk.

There could also be risks to drinking water, the White House warns, as the Environmental Protection Agency rolls back “most” of its inspection activity at hazardous waste sites and drinking water and chemical facilities. The White House also suggested that “efforts to address dangerous contaminants like PFAS – which are linked to severe health effects, including cancer – would be delayed, and cleanup activities at Superfund sites would slow or cease.”

Arts, culture and the great outdoors

A government shutdown could affect some of the country’s most beloved treasures such as national parks and museums.

The National Park Service plans to close most US national parks in the event of a shutdown, following lessons learned in past shutdowns, with trash piling up, toilets overflowing and visitors committing acts of vandalism while the park service’s workforce was reduced.

“In the event of a lapse in the annual government appropriations, National Park Service sites will be closed. The parks depend on Congress and appropriations to pay staff salaries and keep the parks running. This means that the majority of national parks will be closed completely to public access,” a senior administration official said.

Some parks, like the National Mall in Washington, DC, and Gateway National Park in San Francisco, are clearly physically accessible to the public and would remain so, the official said, but “will face significantly reduced visitor service,” such as trash collection, restrooms and sanitation.

Elsewhere, visitors should expect locked gates, closed visitor centers, and no trail or road condition updates as thousands of park rangers would be furloughed, the official said, encouraging the public to not visit during a shutdown “out of consideration for protection and natural cultural resources, as well as visitor safety.”

And Katmai National Park and Preserve’s annual social media darling, “Fat Bear Week,” would be canceled as the employees in charge of its website would be furloughed.

National forests, managed by the US Department of Agriculture, would also be closed, per Agriculture Secretary Tom Vilsack.

However, if there’s a shutdown, some states plan to use their own funds to keep the national parks within their borders open. Utah intends to keep the Mighty 5 parks – Arches, Bryce Canyon, Canyonlands, Capitol Reef and Zion – open, while Arizona plans to keep the Grand Canyon open. Colorado would also keep its four national parks and other federal lands open.

The Smithsonian museums and the National Zoo would remain open at least until October 7 by using prior-year funds. The Smithsonian plans to update its status next week.

Some presidential libraries would be closed, according to the National Archives and Records Administration’s plans.

Student loans and education

The Department of Education previously warned that there could be “some level of disruption” to large student aid programs, including Pell Grants, during a shutdown. “As a result of the permanent and multi-year appropriations, some basic operations (such as processing Free Applications for Federal Student Aid, FAFSA, disbursing Pell Grants and Federal Direct Student Loans, and servicing Federal student loans) could continue for a very limited time; these operations could also experience some level of disruption due to a lapse,” the department said in its 2021 guidance.

The nation’s schools could also face disruptions in federal funding, with the Department of Education warning in that guidance that a delay beyond one week “would severely curtail the cash flow to school districts, colleges and universities.” That memo also notes that approximately 1 in 10 school districts receives more than 15% of its funds from federally funded programs.

The White House also warns that approximately 10,000 children across the country “would immediately lose access to Head Start” programs, impacting some of the nation’s youngest citizens.

Food assistance

Those enrolled in the Supplemental Nutrition Assistance Program, or SNAP, as food stamps are formally known, would receive benefits through October, but what happens after that is unknown, according to the US Department of Agriculture. However, the agency does not have sufficient funding to support normal operations of the Special Supplemental Nutrition Program for Women, Infants and Children, known as WIC, beyond a few days into a shutdown – though individual states may have additional money to continue the program.

“Nearly 7 million pregnant moms, new mothers and young children count on WIC every single day to receive support,” Vilsack told reporters at the White House earlier this week. “With a shutdown, what we would see across the United States is a denial of those benefits and opportunities. In some cases, it would be literally within a matter of days after the shutdown. In some cases it may be in some states, it may be literally in a matter of weeks. But clearly, during the course of a shutdown, millions of those moms, babies and young children would see a lack of nutrition assistance.”

Food banks wouldn’t be able to place new orders and some of their existing deliveries could be disrupted.

Plus, a government shutdown would lead to a delay in federal reimbursements to Meals on Wheels, which could force some community-based programs to suspend meal services; initiate or expand waiting lists; reduce the number of meals they deliver or the number of days on which they deliver; or even shut down, said the nonprofit, which delivers meals to more than 2.8 million seniors annually.

Housing assistance

The 2018-2019 shutdown caused uncertainty for tens of thousands of low-income tenants who rely on the federal government to help pay their rent. The Department of Housing and Urban Development wasn’t able to renew roughly 1,650 contracts with private building owners who rent to poor Americans, many of them elderly or disabled. The agency asked landlords to draw on their reserves to cover any shortfalls.

HUD officials suggested at the time that the expiration of the rental contracts likely wouldn’t prompt landlords to begin eviction proceedings immediately. But the building owners may have had to delay repairs or suspend services they provide, such as transportation, after-school care or social programs, experts said. It’s still unclear how many contracts would be impacted by a shutdown this time.

Campaigns

The Federal Election Commission, the country’s main agency related to securing elections and enforcing federal campaign finance law, would be severely impacted by a shutdown.

“Virtually all core agency functions” of the FEC would cease, per the agency’s plans. That includes review of campaign finance disclosure reports and enforcement of the Federal Election Campaign Act, as well as assistance to campaign and political committee treasurers and members of the public on campaign finance laws.

Research

Numerous government agencies involved in research would be forced to cease those efforts during a government shutdown. For instance, NOAA – the National Oceanic and Atmospheric Administration – would end “most research activities.” And no new National Science Foundation grants would be awarded.

Recruitment

Efforts to recruit new hires across government agencies would be significantly curtailed during a shutdown. It could impact recruitment, selection and placement for the Peace Corps; all civil service jobs at the State Department, according to its 2022 guidance; and all new contractors at the Defense Department, among many others.

The border

US Border Patrol agents are considered essential and would continue to perform their law enforcement functions, including apprehending migrants crossing the border unlawfully, during a government shutdown – but without pay.

A senior Customs and Border Protection official told CNN that the agency would remain focused on its border security mission, as well as facilitating trade and travel. Immigration and Customs Enforcement would also continue its law enforcement duties.

An estimated 59,066 CBP personnel are expected to remain working during a lapse in appropriations and estimated 16,766 employees will be considered exempt/excepted at ICE in the event of a shutdown, according to a Homeland Security document detailing the agency’s procedures.

US Citizenship and Immigration Services, which also falls under DHS and is tasked with processing asylum claims, would continue work that’s fee-funded.

Even though border authorities would keep working, a shutdown could harm other operations.

In previous shutdowns, for example, the Department of Homeland Security was forced to delay maintenance of facilities, “which had a serious impact on law enforcement officer operations and safety, including at the border,” according to a 2019 congressional report that reviewed the cost of past government shutdowns.

“The lack of these critical maintenance and repair services endangered the lives of law enforcement officers and created significant border security vulnerabilities,” the report states.

Disaster recovery

Nearly 2,000 long-term disaster recovery projects would be delayed in the event of a government shutdown.

Federal Emergency Management Agency’s “dwindling” relief fund has already forced it to “prioritize only immediate lifesaving and life sustaining operation,” the White House said. A shutdown would leave the fund underfunded and continue to delay those projects. Examples include a school in Tennessee trying to rebuild after a tornado and a senior citizen care facility that needs to be rebuilt after a hurricane.

This story has been updated with additional reporting.

CNN’s Priscilla Alvarez and Nikki Carvajal contributed to this report.