With an eye on rising seas, a report in Rhode Island offers a long list of wastewater infrastructure recommendations
Climate change has created new challenges for wastewater plant operators, and those tests are likely to increase. But thanks to recent research, Rhode Island is gearing up for the task.
A new study has examined the potentially accelerated risks climate change poses to the state’s wastewater collection and treatment infrastructure. Specifically, it looks at the effects of rising sea levels and the likelihood of more severe rainstorms, which scientists predict will occur as the Earth’s climate continues to change.
The report makes about 270 recommendations for improvements to better prepare state treatment plants and pump stations against flooding, storm surge and other severe-weather effects.
“Rhode Island is the Ocean State,” says Bill Patenaude, a principal engineer with the Rhode Island Department of Environmental Management’s Office of Water Resources. “We’re right on ground zero when it comes to climate change from an inland and marine point of view. We’ve already been seeing heavier precipitation and sea-level rise.
“This study originated because we started seeing these impacts going back to the late 1990s and early 2000s. Because I’ve worked for 28 years in this office, I get a good idea of the trends seen by increased precipitation”
The culmination occurred in 2010, when a series of heavy rain events overflowed the Pawcatuck and Pawtuxet rivers, flooding two treatment plants, seriously affecting two others and taking down two major pump stations. The state has 19 major wastewater treatment facilities, which treat about 120 million gallons of wastewater every day. Because wastewater infrastructure is typically built at low elevations, often near river or coastal flood plains, they are especially at risk for flooding.
Pumping was underway at the flooded Warwick Sewer Authority two days after historic flooding of the Pawtuxet River overtopped its 18-foot protective levee. —Photo Courtesy of the State of Rhode Island
The new $222,900 report — which was mostly paid for through a federal grant — was commissioned by the Department of Environmental Management and Rhode Island’s Executive Climate Change Coordinating Council. It was then prepared over two years by the engineering firm Woodard & Curran. It assessed the potential impacts to the state by natural hazards associated with climate change, made preliminary assessments on climate-change effects to Rhode Island’s wastewater infrastructure, refined those assessments and risk of impacts, developed recommendations for adaptive strategies, and then compiled the work in a report. The state also offered the study data online and provided outreach materials for officials and the public.
“We knew from the beginning that one of the most critical data assets we could capture is the institutional knowledge of the men and women who work at the plants,” Patenaude says.
The study’s conclusions show a need for action. Flooding, debris management and the possibility for bypasses are the major concerns. In fact, Patenaude says, the report determined that seven of the state’s 19 major treatment plants would see substantial flooding during a 100-year storm when climate impacts are figured in.
The study proposes adaptive strategies in five categories: constructing walls and dikes, and flood-proofing; elevating or relocating equipment or systems; standardizing equipment or stocking spare parts; improving the redundancy of components or entire treatment systems; or, as a last resort, controlling flow to surface waters to avoid public flooding inland.
The initiative also helped the state provide planning and design guidance for future wastewater systems. Rhode Island adopted and modified regional planning and design guidance from the New England Interstate Water Pollution Control Commission, which identified two goals for future designs: improvements that would provide continuous operation up to a specified flood elevation and improvements that would consider the survivability of the structural and electrical components of plants to a higher specified flood elevation.
And time, Patenaude says, is of the essence, because Rhode Island faces the double whammy of marine and inland effects from climate change. On the marine side, water levels in Narragansett Bay have risen by about 9 inches in the past century.
The Pawtuxet River in Rhode Island overtops the 18-foot protective levee at the Warwick Sewer Authority during historic flooding on March 31, 2010. The facility was eventually completely submerged. The WSA has since elevated the height of the levee to protect it from 500-year flooding events. —Photo Courtesy of Warwick Sewer Authority
“The clock is really ticking on the coast because of sea-level rise,” he says. “Rhode Island is a big bay with lots of islands. We’re very sensitive to what the sea is doing around us. So, I suppose that one piece of good news for coastal systems is that they have some ability to plan based on sea-level rise projections.”
However, Patenaude says the potential inland impacts of climate change really concern him because it’s difficult to predict catastrophic downpours and the floods they cause.
That sounds ominous, but the report’s 270-plus recommendations revealed some good news.
“The big thing is out of those 270, 150 of them would cost less than $50,000, so it’s manageable,” Patenaude says.
During the 2010 floods, a small cement wall that cost about $10,000 to $15,000 protected a ground hatch from flooding, saving millions of dollars of equipment in tunnels below.
“That’s just an example of being smart at how you look at your facility,” he says. “We know our wastewater operators know their plants better than anyone. They’ll know how to harden things up.”
Patenaude added that Rhode Island will rely on its wastewater plant operators as it implements the study’s recommendations and continues to adapt to climate change.
“That’s where you get some of your best information and some of your most practical information about how to do things right. We began with the front-line crews in operations and maintenance, we’re ending with them, and we’re telling design engineers that they have to work with plant operators for input on how to best protect the plants.”