On a hot day in the summer of 2014, in the Civic Park neighbourhood where Pastor R Sherman McCathern preached in Flint, Michigan, water rushed out of a couple of fire hydrants. Puddles formed on the dry grass and splashed the skin of the delighted kids who ran through it. But the spray looked strange. “The water was coming out dark as coffee for hours,” McCathern remembered. The shock of it caught in his throat. “Something is wrong here.”

Something had been wrong for months. That spring, Flint, under direction from state officials, turned off the drinking water it had relied upon for nearly 50 years. The city planned to join a new regional system, and while it waited for it to be built, it began bringing in its water from the Flint River. McCathern didn’t pay much attention to the politicking around all this; he had enough to worry about at his busy parish.

But after the switch, many of his neighbours grew alarmed at the water that flowed from their kitchen taps and showerheads. They packed public meetings, wrote questioning letters, and protested at city hall. They filled plastic bottles to show how the water looked brown, or orange, and sometimes had particulates floating in it. Showering seemed to be connected with skin rashes and hair loss. The water smelled foul. A sip of it put the taste of a cold metal coin on your tongue.

But the authorities “said everything was all right and you could drink it, so people did,” McCathern said later. Residents were advised to leave the taps on for a few minutes before using the water, to get a clean flow. As the months went by, the city plant tinkered with treatment and issued a few boil-water advisories. State environmental officials said again and again that there was nothing to worry about. The water was fine.

Whatever their senses told them, whatever the whispers around town, whatever Flint’s troubled history with powerful institutions telling them what was best for them, this wasn’t actually hard for people like McCathern to believe. Public water systems are one of America’s most heroic accomplishments, a feat so successful that it is almost invisible. By making it a commonplace for clean water to be delivered to homes, businesses and schools, untold lives have been saved from cholera, dysentery and typhoid fever. In Flint, the water supply was instrumental in turning General Motors – founded in 1908 in Vehicle City, as Flint was known – into a global economic giant. The advancing underground network of pipes defined the growing city and its metropolitan region, which boasted of being home to one of the strongest middle classes in the country.

But in the latter part of the 20th century, GM closed most of its plants in the city and eliminated almost all of the local auto jobs. Smaller companies followed suit or simply shut down for good. Between 1998 and 2013 alone, nearly 150 of them left the downtown area. With the shuttered businesses came shuttered houses and schools. More than half the population, which had reached a high point of nearly 200,000 in 1960, disappeared. Some 22,000 people left between 2000 and 2010.

The empty structures they left behind were both disheartening and dangerous, not only because they were prone to break-ins and fires, but also because they literally crumbled on to the sidewalks where people passed by. Civic Park’s tree-lined avenues of historic homes became blighted by vacancy. At the same time, the Flint metro region – that is, the suburbs – grew exponentially. It was a widening circle of wealth with a deteriorating centre.

With so much lost, Flint needed help. An emergency plan. A large-scale intervention of some kind. But in fact the state of Michigan exacerbated Flint’s woes by dramatically reducing the money that it funnelled to its cities. Between 1998 and 2016, Michigan diverted more than $5.5bn in tax revenues – which would ordinarily go to places such as Flint, to power streetlights, mow parks and plough snow – and used it to plug holes in its own budget. At the same time, Flint suffered the Great Recession, the mortgage crisis and a major restructuring of the auto industry.

If you wanted to kill a city, that is the recipe. And yet Flint was very much alive. In 2014, the year of the switch to a new source of drinking water, it was the seventh-largest city in the state. For about 99,000 people, Flint was home. And they did what they could to fill the gaps. When Pastor McCathern and his congregation at Joy Tabernacle realised that Civic Park was not on anyone’s list of priorities, they launched their own initiatives to fix up the neighbourhood. They covered the windows and doors of vacant properties, and paid young men to mow lawns and board up empty homes.

“The community was at one time totally ignored by everybody,” McCathern said. “But because young people stood up, now everybody came on board.” You could feel a shift in the momentum. You could see the change. “It was a different Flint that was coming.”

But on that sweltering summer day, there was that water pouring out of the fire hydrant, as children sprinted back and forth through its spray. Dark as coffee.

This is the story of how the city of Flint was poisoned by its own water. It was not because of a natural disaster, or simple negligence, or even because some corner-cutting company was blinded by profit. Instead, a disastrous choice to break a crucial environmental law, followed by 18 months of delay and cover-up by the city, state and federal governments, put a staggering number of citizens in peril.

In a city with plenty of urgent matters competing for attention – poverty, vacancy, schools, crime, jobs – one thing Flint didn’t have to worry about before the spring of 2014 was the quality of its water. The Detroit water and sewerage department (DWSD) had supplied Flint with good water for nearly 50 years. The big public utility drew from the freshwater of Lake Huron, a lake so deep and fierce that it once swallowed eight ships in a single storm. Flint’s own treatment plant, which it had used to treat its river water before joining the DWSD in the 1960s, sat idle. It remained on hand only because the state required a backup water source for emergencies.But while the quality of DWSD water was reliable, its cost was not. Residents had urged their leaders to relieve the burden of pricey water. Monthly rates in Flint were among the most expensive in the country, and yet 42% of residents lived below the federal poverty level. And the rates kept rising – a 25% increase here, a 45% increase there. Many residents just couldn’t afford their bills. But at this point it was difficult for the city to do much about it. Its infrastructure was built to serve Flint when it had twice the people it had now; to maintain it, fewer ratepayers had to carry a heavier burden……………….When residents noticed there was something odd about their water, they asked for help. They organised. They made themselves seen. But they were routinely dismissed. Among the many ravages attributed to the water crisis – the rashes, the hair loss, the ruined plumbing, the devalued homes, the diminished businesses, the home owners who left the city once and for all, the children poisoned by lead, the people made ill or killed by Legionnaires’ disease – perhaps the most devastating was that people lost faith in those who were supposed to be working for the common good. That this happened in the Great Lakes State, which is surrounded by one-fifth of all the freshwater on the face of the Earth, makes it all the more haunting.

What happened in Flint reveals a new hydra of dangers in civic life: environmental injustice, the limits of austerity, and urban disinvestment. Neglect, it turns out, is not a passive force in American cities, but an aggressive one.

The Poisoned City: Flint’s Water and the American Urban Tragedy by Anna Clark is published by Metropolitan on 10 July