The water came in fast, and nothing could be done to stop it.

As the remnants of Hurricane Ida deluged the region last month, Marc Lucca, the president of Aqua Pennsylvania, watched live security cameras as employees at the Pickering West water treatment plant splashed through ankle-deep water gushing into the facility. “In a matter of minutes, they were hip-deep in water and had to evacuate,” he said.

Floodwater laden with mud and debris poured into the Chester County plant from three directions, disabling operations for nine days and affecting service to about a million people in Delaware, Chester, and Montgomery Counties. “We saw seven to eight inches of rain, two inches an hour,” said Lucca. “We’re seeing an intensity of these storms that we’ve never seen here before.”

More than a month after the storm, Pickering West is operating at only half capacity, and might never be fully restored.

Seventy miles away, in Bridgewater, N.J., the operators of New Jersey American’s Raritan-Millstone Water Treatment Plant also experienced an unexpectedly rapid rise of Ida’s floodwaters.

Tom Kantor, a maintenance mechanic, was driving toward the plant for the midnight shift when his pickup truck stalled in high water. He was rescued by a public works employee in a construction vehicle. But Kantor’s four-month-old Dodge Ram floated away, a total loss.

“The DPW guy brought me up and I made it in before we closed the gate,” Kantor said. He and his coworkers were marooned in the treatment plant for more than two days before the waters subsided.

The Raritan-Millstone plant, unlike the Pickering plant in Pennsylvania, stayed dry and continued operating, thanks to a new $37 million flood wall completed only three years earlier that held back the high water.

That new wall was built after a hurricane 10 years ago came within one inch of flooding the plant. This time the flood crested nearly a foot above the level of the old wall. Without the new wall’s additional four feet, the flood would have swallowed the plant, which serves about 1.5 million people in central New Jersey.

“That wall paid dividends in just a few years,” said Oleg Kostin, the director of operations for New Jersey American. “If this plant had gone down, I guarantee it would cost more than $37 million to bring it back online.”

The experiences at the two water treatment plants illustrate the risks and costs associated with ever-more severe storms that threaten the region’s energy, transportation, and water infrastructure. Water-industry experts say that extreme weather events, caused by climate change, pose a growing threat to drinking-water systems, many of them located in flood-prone areas along rivers.

In the aftermath of Ida, water utility operators are reassessing their systems’ vulnerabilities and whether it is more cost-effective to harden existing facilities or to move equipment or plants to higher ground. The risk: more floods, greater cleanup costs, and possibly the nightmare scenario for a water system -- a prolonged loss of service to a large population. Imagine the run on bottled water and portable toilets.

“What do we keep here?” said Lucca, surveying the damage on a recent tour of Pickering West, which is near Phoenixville, adjacent to the smaller Pickering East plant. “What do we flood-proof here? What about the flood wall? Do we move over to our Pickering East facility, where we have space?”

The temporary loss of the Pickering West plant, Aqua’s largest suburban Philadelphia treatment facility, caused the company to impose a boil-water advisory in two towns for several days and to plead with thousands of customers to curtail consumption so that storage tanks did not empty out. Aqua’s challenges were compounded because several neighboring water suppliers, which are interconnected to Aqua’s system, also experienced Ida-related outages and had little spare capacity to offer.

In Doylestown and Norristown, water-main breaks caused by washouts and sinkholes disrupted service to pockets of customers.

In Tullytown, a chemical treatment system failed at the Lower Bucks Joint Municipal Authority plant as the system struggled to cope with filthy floodwaters from the Delaware River, said Vijay Rajput, the authority’s managing director. Rajput shut down the plant rather than sending out impure water to Bristol and other surrounding communities, but customers were advised to boil water for four days until the system recovered.

In Philadelphia, floodwaters damaged the raw water intake pumps on the Schuylkill, forcing the Philadelphia Water Department to suspend operations for nearly two weeks at the Belmont Water Treatment Plant. The department was able to make up for the loss of the smallest of its three treatment plants by stepping up output from the two other facilities.

But had a similar outage knocked out the Baxter Water Treatment Plant on the Delaware River, which supplies more drinking water than the two other plants combined, the outcome for Philadelphia might have been different.

The costs for recovering from Ida and for future fortifications to water systems will inevitably be passed on to customers in the form of higher rates.

“Right now we’re focused on what’s the long-term solution,” said Christopher Franklin, chief executive officer of Aqua’s parent company, Essential Utilities Corp. of Bryn Mawr. “We’ll have to think about what are the trade-offs and the benefits, and what it would cost in rates. That’s a real conversation.”

Water customers are already stressed from picking up the tab for infrastructure upgrades. Twelve days before Ida hit, Aqua Pennsylvania filed a request to increase water bills for 445,000 customers by 17% and sewer bills by almost double that, to about $155 a month for a customer with combined Aqua water and wastewater service. A generation ago, water bills were so low that utilities billed quarterly.

It’s not just Aqua: Across multiple jurisdictions, bills for water and wastewater customers have been increasing in recent years at a quicker pace than fees charged by other regulated utilities, such as electricity and gas suppliers. The water bills are magnified by the cost of replacing water and wastewater systems installed five decades ago to meet federal clean-water laws passed in the early 1970s. Those systems are reaching the end of their useful lives.

“A lot of that infrastructure was designed to last 40 or 50 years, and it was also designed as if the climate of the future was going to mirror the climate of the past, which has proven to be not true,” said Scott Berry, director of policy and government affairs for the U.S. Water Alliance, an advocacy group representing public and private utilities, along with community, business, and environmental nonprofits.

The massive water and wastewater civil works of the 1970s and 1980s were partly underwritten by grants from the federal government. But Washington’s support for water and wastewater infrastructure has diminished over the decades to about 4% of total current costs, said Berry. The cost of responding to bigger storms and more floods will largely fall on local users.

There is some hope for financial relief from the federal infrastructure package currently mired in Congress. The legislation initially included $111 billion for water, wastewater, and storm-water infrastructure, a big increase over previous years. That compares with the $473 billion that the Environmental Protection Agency estimated in 2015 was needed over the next 20 years just to maintain and improve the nation’s drinking-water infrastructure, not counting sewers.

A final version of the infrastructure legislation, if it ever passes Congress, is likely to contain much less money for water projects. The latest proposal pared water spending down to $48 billion over five years, said Berry. And most of the money will likely target programs to replace lead household water supply lines, remediate water systems contaminated by PFAS chemicals, and invest in small rural water systems through state loan programs, rather than addressing climate challenges.

Water-industry advocates say the high cost of responding to climate challenges supports arguments in favor of consolidating smaller systems under the control of larger operators, either publicly or privately owned. Consolidation of water and wastewater systems has accelerated in recent years, particularly in Pennsylvania, where state law enables buyers to pay top dollar to acquire municipal systems. Large water operators say they can connect multiple communities into networks with diverse water sources, take advantage of economies of scale, and spread the cost of upgrades across a wider population.

“We understand that people can be very parochial and have a lot of feelings about the idea of having their local water system,” said Mark McDonough, the president of New Jersey American Water, whose parent company, American Water Works Co. Inc., is based in Camden. One of his pitches to local officials who are considering selling their water systems is that a large operator is more likely to have the resources to respond to a disaster.

“Mayors have so much to think about these days,” McDonough said. “Climate variability is causing lots and lots of challenges above ground. They need to really hand off this problem to the experts who can help them run the below-ground stuff.”

The history of New Jersey American’s Raritan-Millstone Water Treatment Plant in Somerset County is a case study in trying to cope with increasingly hostile climate forces.

The plant, which supplies about 150 million gallons of treated water a day to customers in seven counties, is on a flood plain at the confluence of the Raritan and Millstone Rivers. Its owners have increased flood barriers twice in the last 20 years in response to big storms.

There was no flood wall before 1999, when Hurricane Floyd inundated the facility so completely that it required a helicopter rescue of the plant’s staff.

Oleg Kostin, who now oversees all of New Jersey American’s operations, was superintendent of the plant at the time, and the last person hoisted out. “I was the captain going down with the ship,” he said.

Floyd knocked the plant out of service for six days and cost $17 million to clean out and repair. The plant’s previous owner authorized construction of a flood wall and earthworks to protect the plant from a 100-year flood.

That 100-year-flood wall nearly met its match just a few years later, in 2011, when Hurricane Irene’s floods rose to within an inch of topping over the wall. Kostin snapped a photo of the murky water near the top of the wall, using a ruler as a prop.

He calls it the “money shot,” because it was instrumental in persuading New Jersey regulators to authorize the expenditure of $37 million to raise the wall four feet higher, to 500-year flood standards.

Raising the Raritan-Millstone barrier to withstand an epic flood is a more complex engineering challenge than simply adding four feet of concrete on top of an existing wall.

In many places, an entirely new wall needed to be erected with a foundation of steel sheet pilings pounded into the soil as deep as 50 feet to form an underground wall down to the bedrock. That raised the project price significantly. That subsurface barrier is designed to thwart the powerful scouring force of a huge flood, which can undermine a weaker barrier and cause it to collapse.

The Raritan-Millstone, now surrounded by a foot-thick concrete wall and monstrous steel gates, resembles a well-fortified correctional institution. “We joke that we’re going to put up turrets and machine guns,” said Kostin.

Aqua Pennsylvania’s Pickering West plant in Chester County, at the confluence of the Schuylkill and Pickering Creek, also has a history of devastating floods. In 1972, the remnants of Hurricane Agnes filled the plant’s interior to about six feet high, memorialized in a plaque on the wall of the plant’s control room.

More than a decade ago, Aqua spent $20 million to improve the Pickering West plant, which included $1 million to raise the earthworks and walls by 18 inches to meet 100-year storm standards.

“We thought we were over-building it at the time,” Franklin, the Essential Utilities CEO, said on a tour of the damaged plant about a month after the storm. “Clearly they weren’t high enough given what we’re facing today.”

The flood, which came into the plant from three directions, actually outflanked the Pickering West flood wall. The water came up from the Schuylkill, as it usually does in a heavy storm.

But the plant’s operators had never seen the water also overflow the nearby Pickering Dam, filling up Route 23, and then cascading down the plant’s driveway like an uninvited visitor. Runoff from the nearby Moorehouse residential development poured in from a third direction.

The water converged and filled the treatment plant’s buildings to a depth of six feet, coating everything with gooey silt, ruining computerized control systems and banks of electrical switches. It stopped a few inches shy of Hurricane Agnes’ high-water mark from 49 years earlier.

The flood’s force snapped trees and crushed the thick steel cover of a million-gallon tank that stores finished water -- a total loss -- and filled the area protected by the flood wall. The earthen wall, which was designed to withstand the force of water coming from the exterior, collapsed from churning water that eroded the wall from the interior.

After the floods receded, the plant was coated with a slippery gunk. A bridge across Pickering Creek that connects the two plants, submerged under 15 feet of turgid water during the flood, was damaged. Electrical switches and electronics that been submerged needed to be removed and replaced. Muddy river water filled a two million-gallon tank that normally contains treated water. Cleanup workers rescued a carp from the vessel before flushing and disinfecting the tank.

The Aqua executives commended their employees, who escaped injury, for rallying to restore service in nine days. A damage assessment is still underway. The tally will total millions of dollars, though Franklin said some is covered by insurance.

There is a serious discussion underway at Aqua to consider whether it is worth restoring Pickering West to full capacity of 40 million gallons a day, or to build new capacity elsewhere, at a higher elevation.

“These plants were built to withstand most storms and you never expect to see this,” said Franklin. “So now it really challenges you on the engineering side to think about what’s next. What do we have to prepare for?”