One in a series of occasional articles about the regional effects of climate change and how we're coping.

Deep inside the massive steel tank, the light glowed eerily from the freshly painted surface. The voices of visitors who had slithered through a narrow portal echoed.

The soon-to-be refilled vessel, rising from a Limerick Township field, is more than 30 feet high and 75 feet across. It holds a million gallons of drinking water, enough to cover a football field to a depth of four feet.

And it is one sign among many the future of water in the region is shifting as a result of climate change. Water companies must adapt.

The rehabbed tank, owned by Pennsylvania American Water, is part of a $16.5 million project to renovate 15 tanks and build nine more - in part, to ensure uninterrupted water supplies during the increasing droughts that climatologists predict for the East Coast.

They also expect more frequent and intense storms. That's why the utility's Voorhees parent, American Water Works Co., is also raising the flood wall around one of its drinking-water plants in North Jersey's Somerset County.

Floodwaters could contaminate the water and disable the plant. The wall was built to create, in effect, a dry island in a storm. But it's no longer high enough.

"The thing we focus on is what we call weather volatility," said Jeff Sterba, American Water's CEO. "It's the volatility that creates the great risk to infrastructure."

From Philadelphia to Bucks and Delaware Counties, larger pipes are going into the ground. Dam spillways are being widened to better accommodate bigger surges in heavier downpours. Drinking and wastewater are inherently linked to rivers, so plants are situated in floodplains that are - or will be - inundated more frequently. Hence, the renovations.

"Whether you agree that climate change is happening or not, you're already paying for it," said Chris Crockett, the Philadelphia Water Department's deputy commissioner for planning. "And it's just the tip of the iceberg."

For now, extra costs are merely "embedded in the numbers" of a project, he said. It's hard to tease out which changes are due primarily to climate change, versus, say, better preparedness overall.

"People haven't seen the big tickets yet," Crockett said. "It's just a matter of time."

The companies have always dealt with uncertainty, of course, whether in drinking water supply, wastewater treatment, or stormwater management: What will the population look like in 20 or 40 years? How will regulations change? Will water-thirsty industries move in, or out?

Now, climate change is being factored in, even though predictions of what will happen - and when - vary widely, particularly when applied locally.

It's more than rain, floods, and droughts. Among the subtler questions: If temperatures rise, will people use more water? And the more obvious: How do you keep water-based facilities operating during power outages caused by floods? (American Water brought in 400 additional generators in advance of Sandy.)

"We're not designing for climate change, but we're designing with climate change in mind," said Howard Neukrug, Philadelphia's water commissioner. "We're looking at everything we do, and every part of our process is designed with future variables in mind."

Most pipes are designed to last 80 to 100 years - another reason companies say planning now is important.

Meanwhile, many of the nation's financially strapped utilities still have pipes that are 150 years old. Or older.

"That's the real risk we run: the infrastructure is becoming so old, and failing, and now you add climate-change impacts to it," Sterba said from his office in Voorhees.

Philadelphia's storm-water "outfalls," many of which drain into the Delaware River, were designed and built more than 100 years ago. The river has risen a foot since because of higher sea levels, and the outfalls are submerged more often.

So, as part of a $30 million upgrade that includes drainage improvements in Germantown, pipes leading to the outfall near the SugarHouse Casino have to be made wider, not deeper, to accommodate greater flows.

The city's ongoing $2 billion project to deal with storm water that often drains into streams because the pipes can't handle it has turned out to be a bulwark against climate change.

Rather than building bigger pipes and bigger storage facilities to hold excess storm water until it can be treated, the focus is on keeping it out of the pipes in the first place by designing rain gardens to capture it, or installing porous pavements to let it soak into the ground.

These can simply be duplicated - not reinvented - if climate change brings even heavier rains.

According to an analysis prepared for the Partnership for the Delaware Estuary, the number of "heavy precipitation events" in the river basin has increased in recent years.

"We're seeing floods where we have not seen them before," Neukrug said.

One rain gauge in Germantown showed the number of "extreme events" - 11/2 inches of rain in 15 minutes - increased from one in the 1990s to three in the decade from 2000 to 2009, to five in the last three years.

Still, Neukrug struggles with how to talk to residents about what's happening. Climate change has become a politically loaded issue, he said. And many people don't really care about the science behind their flooded basements.

"They do not want to hear that this was a 100-year storm. They know they saw the same storm two years ago," Neukrug said. "They do not want to hear it's climate change. They want to know what you are going to do to make them whole, and how you are going to protect them next time."

So the Water Department is coming up with new taglines: "There's a new kind of storm in town," and, "The 100-year storm isn't what it used to be."

In the Pennsylvania suburbs, the main water provider, Aqua America, has multiple reservoirs to ensure enough water supply. Spillways on the dams are being widened or otherwise rebuilt to handle increased storm-water flows.

The dam at the Springton Reservoir can handle flows of 37,000 cubic feet per second. After a $10 million upgrade, it will be able to manage 51,000 cubic feet.

"That is a huge amount of water," said Nick DeBenedictis, CEO of Aqua America in Bryn Mawr.

For an idea of what could happen, he harks back to Hurricane Floyd in 1999. Before the storm, the reservoir was only one-third full, and everyone was worried about a drought. Then, 11 inches of rain poured in. It filled up in one day, and the extra water was gushing over the spillway. Everyone downstream was worried the dam would break.

Aqua America, like American Water, is "hardening" its flood-prone facilities.

It raised the intake pump assembly 12 feet when it revamped its drinking-water plant on the Pickering Creek near Phoenixville. The seven-foot protective floodwall outside is being raised 18 inches.

When it comes to climate change predictions, "it's not like we know the answer," DeBenedictis said. "We just know there could be a variance, up and down, and we're preparing for both."

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