Traffic on Interstate 66 near the Vienna Metro Station in 2015. (Nikki Kahn/The Washington Post)

Virginia legislators agreed on reforms to the proffer system, which local governments use to negotiate payments from developers to fund public infrastructure. But the debate over infrastructure funding revealed a worrisome fact: Virginians flat-out can’t afford the state’s unsustainable level of population growth.

The population boom is overburdening public infrastructure and resources on which all citizens depend, and it threatens to raise the cost of living to astronomical levels.

To solve this looming crisis, Virginia’s leaders have to stabilize the state’s population growth.

Virginia’s population increased 35 percent from 1990 to 2015, to nearly 8.4 million people. So far, we’ve been able to accommodate this growth with high-rise apartments and beefed-up mass transit. But what happens by 2040, when Virginia’s population is expected to grow by an additional 25 percent to more than 10.5 million?

Our state is rapidly reaching a tipping point at which our already-stressed infrastructure collapses and existing resources are woefully insufficient to rebuild it.

The population boom is happening fastest in urban areas. Population growth has led to sprawl that is swallowing many parts of Northern Virginia.

Average families are struggling to afford high housing and transportation costs. A family of four in Northern Virginia, according to a study by the Richmond-based Commonwealth Institute, requires an income of more than $63,000 per year just to meet a minimal standard of living.

Commuter traffic is a nightmare. In 2013, the average Virginia commute was about an hour each day.

Population growth also is degrading our water supply. Back in 2006, a U.S. Geological Survey report highlighted the pressure population growth and urban sprawl were putting on water resources. A 2014 USGS study on the water quality of Fairfax County, the most populous county in Virginia, suggested that more than a decade of population growth had caused “streams throughout Fairfax County [to be] . . . generally of poor health,” noting that watersheds in intensely developed areas were of the poorest quality.

Fortunately, there is a way to address these alarming trends before it’s too late — and it doesn’t involve politically divisive family planning measures. Merely slowing the pace of immigration would enable Virginia (and the nation) to manage its expanding population.

The Pew Research Center projects that the U.S. population will swell to 441 million by 2065, an increase of 117 million people from today. Immigrants and their children will account for 88 percent of that population boom.

That sort of growth can’t be sustained over the long term, particularly in places such as Virginia, where the immigrant population increased at twice the national average between 2000 and 2010.

Virginia’s foreign-born population has exploded since 1990, growing by more than 200 percent. Immigrants now account for 1 in 9 state residents.

Immigrants have children at a higher rate than people born in the United States, so slowing immigration would have an outsize effect on overall population growth. Immigrants were responsible for 45 percent of Virginia’s total population growth in recent decades when their U.S.-born children are taken into account.

University of California at San Diego economist Gordon Hanson found that immigration compounds many of the negative effects of population growth and sprawl, particularly by driving up housing costs.

To be clear, changes to immigration policy shouldn’t harm current legal immigrants. Rather, the immigration system should be reformed in a way that reduces total immigration from its current unsustainable level of about 1 million new permanent residents per year, the highest influx of any nation in the world.

Limiting immigration would help ensure responsible population growth so that future generations — regardless of their national origin — can enjoy a prosperous and powerful commonwealth for decades to come.

The writer is a member of Virginians for Quality Healthcare.