Battle With The Sea: Protecting Wastewater Treatment Plants

Dec 18, 2014

Here’s an effect of climate change you might not have thought of: heavy rains flood wastewater treatment plants. These intense rain storms are one result of warming temperatures. As part of our ongoing series, Battle With The Sea, Rhode Island Public Radio’s environmental reporter Ambar Espinoza has a report from a wastewater treatment plant in Warwick.

The Warwick Sewer Authority is located on the banks of the Pawtuxet River, next to what is called an oxbow, the U-shape curve in a river. The river wants to fill in the land next to the oxbow each time it floods. 

The river has a history of flooding sometimes across the treatment plant all the way to Interstate 95 on the east side of the plant. Superintendent Patrick Doyle said that's why in the mid-1980s the treatment plant operators built a levee to protect the facility from river flooding. 

Patrick Doyle, superintendent of the Warwick Sewer Authority, stands in front of the levee that was overtopped during the Great Flood of 2010 and wiped out the facility. There was no sewer service for an entire week.
Credit Ambar Espinoza / RIPR

"We have old pictures of guys in boats paddling around the plant and when they built it in the mid-80s and finished around '87, '88, we haven't had a flood inside the facility,” said Doyle.

That levee was built to protect against a 100-year storm. Then came the Great Flood of 2010, which overtopped the levee, flooded six pumping stations along the river, and caused a major power outage. There was no sewer service for a full week. If the levee had been higher, Doyle believes the levee would have protected the facility against this historic flood. This is why work is underway to raise the levee to protect the facility against 500-year storms.

Doyle walks out of the operations building at the plant to describe the completed work so far.

“This pile of dirt you see over here is loom that they stripped off the top of the existing levee so they could build it with the right type of materials,” he said.

The levee, about 2,300 feet long, wraps around the treatment facility to the north, south, and west sides. Interstate 95 sits to the east. The north and south sides have already been elevated by adding mounds of earth on top of it.

But Doyle said construction workers stumbled upon obstacles when they began work to reinforce the west side of the levee, where they were going to install flood walls.

“There were boulders in the fill of the levee that we don’t think were supposed to be there from the original construction, and if we take a walk over here, you’ll see them,” Doyle said.

He points to a section of the levee with a bunch of boulders at the bottom of it. Construction workers tried, unsuccessfully, to install flood walls several feet down the middle of the levee. The flood walls wouldn’t take. 

Credit Ambar Espinoza / RIPR

“And you can see that the tops of them are shattered,” said Doyle. “When we pulled them out to check the condition of the bottom, they were all broken at the bottom, too.”

Stumbling across these boulders is a minor setback for the elevation work. Doyle said it actually presents an opportunity to finish the levee with more mounds of earth, as long as they can secure the permits to do that.

“Now we’re finding out that the earth is the cheapest construction and it has a longer life cycle than the sheeting or concrete wall,” he said.

This work has to be done in preparation for anticipated intense rains due to climate change.

Six pumping stations that belong to the Warwick Sewer Authority were completely flooded during the 2010 flood. Pictured here is the pumping station along Knighting Street in Warwick.
Credit Photo Courtesy of Janine Burke

In the past six years, the treatment plant has been through three federally declared disasters, including the complete wipe out of the plant in 2010, said Janine Burke, the executive director of the Warwick Sewer Authority. She can personally attest to the increasing number of intense rainstorms.

“I don't know what the data is or the science is. I can tell something different is going on, because the number of these events has increased dramatically just in the last 6 or 7 years that I've been working in the field,” said Burke. “So I guess that would be my experiential data. It's [climate change is] happening. And you need to get prepared for it and you need to prepare your infrastructure. Or you'll be out of commission.”

It cost $14 million to recover from the damages. And a federal grant will cover the estimated $2 million to raise the levee. Burke sees that as savings from future catastrophic storm damages and all the overtime it takes to recover.

The good news, added Burke, is that the state is taking climate change threats seriously. She said the state’s treatment facilities and their pumping stations are going to last 50 to 75 years, so everyone involved has to be conscious about that. 

“And usually local government is not very good at looking at that kind of long term planning but something else is going on in Rhode Island,” she said. “There's a lot of good people thinking about this and really trying to keep it on the front burner and moving forward.”

Roughly within the next three months, the Department of Environmental Management will conduct vulnerability assessments at all of the state’s 19 wastewater treatment facilities.

“We’re going to have rain storms and flooding no matter what,” said Bill Patenaude, principal engineer at the DEM’s office of water resources. “So we do need to look at how facilities respond to not just what we think is going to happen, but what is happening. We know from the National Weather Service that there are trends in increased precipitation intensities, so we need to plan for that, no matter what the cause is.”

Patenaude said all of the treatment plants are at risk for flooding, storm surges, and power outages, because these facilities were built in low-lying areas with gravity in mind.

Workers at the Warwick Sewer Authority took this photo before they evacuated the facility during the 2010 floods. Wastewater treatment facilities have been built in low lying areas, so that the sewage in the system will flow naturally to that point to be treated.
Credit Photo Courtesy of Janine Burke

“So that means when you're designing collection systems, and wastewater treatment facilities, you design them at low points, so that the sewage in the system will flow naturally to that point to be treated,” said Patenaude. “It’s much cheaper to do it that way. You use gravity as your friend in the wastewater world.”

That is, until the sea and the rivers start to respond to these manmade changes along shorelines and to the climate. Patenaude said there’s a lot at risk if the state doesn’t prepare for future climate change impacts. Rhode Island’s 19 wastewater treatment plants treat 100 million gallons of wastewater daily.

“We produce that every day. That has to be treated,” said Patenaude. “That has to be treated to exacting standards. So that we don’t impact what we love so much about our state: our bay, our rivers.”

During the 2010 flood, raw untreated sewage from different treatment plants entered the Pawtuxet River and eventually Narragansett Bay. Other treatment plants discharged raw sewage during Superstorm Sandy, too. So shoring up treatment facilities is also a public health concern. 

Patenaude said these vulnerability assessments will take a look at how climate change affects weather. And it will examine what changes plants will have to make – from moving or elevating pumping stations to installing protective walls. Facility managers will need to identify in what order of priority they should pursue those changes.

The rocky section of the levee (to the left) still has to be elevated. The levee (to the right) has been elevated 5 1/2 feet already at the north and south sides.
Credit Ambar Espinoza / RIPR

Raising the levee was a top priority for the Warwick Sewer Authority. Executive director Janine Burke is pleased with the progress so far as she walks toward the north side of the levee – now 5 ½ feet higher than it was back in 2010.

“The earthen levee--it’ll last forever,” Burke said. “My kids’ grandkids will be looking at that thing. It’s earth. As long as it’s constructed properly and settles properly, it’ll never go anywhere.”

Most of the remaining work to elevate the levee will pick up in the spring.

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