DES MOINES, Iowa (AP) -- Deep inside a 70-year-old water-treatment plant, drinking water for Iowa's capital city is cleansed of harmful nitrates that come from the state's famously rich farmland.
Without Des Moines Water Works, the central Iowa region of 500,000 people that it serves wouldn't have a thriving economy. But after decades of ceaseless service, the utility is confronting an array of problems: Water mains are cracking open hundreds of times every year. Rivers that provide its source water are increasingly polluted. And the city doesn't know how it will afford a $150 million treatment plant at a time when revenues are down and maintenance costs are up.
"We're reaching the end of the life cycle of some of the most critical assets we've got," said Bill Stowe, CEO and general manager of the utility, where the downtown plant was built long before nitrates that can harm infants became a pressing concern.
Around the country, scores of decaying drinking water systems built around the time of World War II and earlier are in need of replacement. The costs to rebuild will be staggering. The costs of inaction are already piling up. The challenge is deepened by drought conditions in some regions and government mandates to remove more contaminants.
At stake is the continued availability of clean, cheap drinking water - a public health achievement that has fueled the nation's growth for generations.
"The future is getting a little dark for something as basic and fundamental as water," said Adam Krantz of the Water Infrastructure Network, a lobbying group that is fighting cuts to key federal water programs.
Unlike pothole-scarred roads or crumbling bridges, decaying water systems often go unnoticed until they fail. But without big changes in national policy, local governments and their ratepayers will be largely on their own in paying for the upgrades. The amount of federal money available is a drop in the bucket. That will mean rising water rates on customers, a trend that expected to continue for years.
"That's the key that Americans have to understand: If they want this system, they are going to have to be willing to finance it," said Greg DiLoreto, past president of the American Society of Civil Engineers, which has warned of a future with more equipment failures that will disrupt water service, transportation and commerce.
More than a million miles of underground pipes distribute water to American homes, and maintaining that network remains the largest and costliest long-term concern.
As they get older, they fail in different ways. Some split and rupture, with an estimated 700 main breaks occurring around the U.S. every day. The most devastating failures damage roadways, close businesses and shut off service for hours or days.
Utilities have long struggled to predict when to replace pipes, which have vastly different life cycles depending on the materials they are made from and where they are buried. Experts say a peak of up to 20,000 miles of pipe will need to be replaced annually beginning around 2035, up from roughly 5,000 miles currently. Each mile can cost $500,000 or more.
The impacts are playing out across the nation. The Philadelphia water department, the nation's oldest, is already spending tens of millions of dollars more per year to replace its worst pipes. Yet the city saw more than 900 water main breaks in the most recent budget year. In June, two massive breaks forced evacuations and damaged cars, homes and businesses.
New Orleans once boasted about not raising water rates for two decades. But in 2012, the city approved 10 percent increases on water bills for eight straight years as part of a plan to fix its crumbling system. The average household's monthly water-and-sewer bill will climb to $115 by 2020.
The massive main break that flooded the UCLA campus in Los Angeles in 2014 was widely seen as a wakeup call for failing infrastructure.
Pipes aren't the only components in need of big investments. Many treatment plants are old and need to be replaced or rebuilt at a cost of tens of millions of dollars even in small cities. New valves to control water flow, new pumping stations to keep up pressure and new tanks to store water are also needed.
The demand for investment comes as revenue is falling, in large part because Americans are using less water and installing more efficient toilets and showerheads. Many households affected by drought have also cut their usage, either voluntarily or because of mandatory orders. That is good for conservation but starves water systems, which charge customers based on the amount used.
Facing the loss of income, many have been forced to raise rates. Customers are essentially paying more for using less.
Costs are also rising to accommodate federal regulations that require removal of more potentially harmful contaminants.
Many of these pressures are colliding in Des Moines, where the utility is considering a rate hike for customers of about 10 percent for next year.
Des Moines Water Works is fighting nitrate levels that are often far above the federal standard for safety in the two rivers that provide its source water. Nitrates are often the result of farm runoff that is tainted with fertilizer and manure, and removing them is expensive because they aren't addressed in the normal treatment process.
The water agency has taken the unprecedented step of suing three major Iowa farming counties in federal court to try to limit the farm discharges. But the litigation has provoked intense criticism from Iowa's powerful agricultural industry, which argues that farmers are already taking voluntary measures to control them. If the problems persist, Stowe said, the utility will have to spend $150 million to build a nitrate-removal plant.
The treatment costs also leave less money to replace Des Moines' aging pipes. The effects are felt by residents such as Mario Tumea, whose family's Italian restaurant was closed in May for a day and a half after a 12-inch cast-iron main from 1938 split and sent water gushing into the street.
"It's frustrating," he said. "But when you have old pipes and stuff like that, it's going to happen."