High-tech sewer tool
A 4,200-mile web of underground pipes whisks away Charlotte’s foulest byproduct, its sewage, safely out of sight and smell. Until it’s not.
About five times a week, clogged or broken pipes send sewage flowing toward the nearest creek or lake. A summertime splash in the water becomes a frolic with bacteria, parasites and viruses.
Records show that spills by Charlotte Water, the city’s utility, have dropped since 2007. That was the year the Environmental Protection Agency sanctioned the city for Clean Water Act violations.
The number of spills per mile of pipe has dropped by nearly half since then. The volume of sewage released in the past five years is half that of the previous five.
Still, spikes continue: Nearly a half-million gallons of sewage reached surface water between mid-2013 and June 2014. Close to 600,000 gallons spilled in fiscal year 2012 and 660,000 gallons – the volume of an Olympic-size swimming pool – in 2010.
It’s a problem all cities wrestle.
EPA estimates that U.S. utilities release 3 billion to 10 billion gallons of sewage a year. Contact with the brews of human, household and industrial wastes can trigger infections, stomach flu, diarrhea, cholera and hepatitis.
The Mecklenburg County Health Department says it’s not aware of a case in which disease has been linked to sewage in creeks or lakes. “It is on our radar, and when (spills) occur we work in cooperation with environmental protection staff to make sure public notification is posted,” said Dr. Stephen Keener, the department’s medical director.
“Our goal is always zero” spills, said Charlotte Water director Barry Gullet, who oversees plants that treat 30 billion gallons of sewage a year. “Our goal is to have less than we had the year before.”
High-tech tools, better use of data and beefed-up maintenance have turned around a utility whose spills soared a dozen years ago.
The human, household and industrial wastes in sewage harbors bacteria, parasites and viruses.
That was the wet year of 2003. Rainwater flooded sewer lines, pump stations and treatment plants. More than 500 spills dumped an epic 20 million gallons of sewage into lakes and creeks.
In response, the utility built basins at treatment plants to store surges of incoming wastewater instead of letting it flow untreated to creeks. A program began to replace and rehabilitate pipes.
Conversations also began with EPA, which enforces federal water laws. That led to a 2007 consent order that included a $125,000 fine, $300,000 in environmental projects and $173 million in infrastructure upgrades.
EPA has filed similar enforcement cases with eight of the Southeast’s nine largest municipal systems since the mid-1990s. Sewage spills by those utilities have also been dropping, the agency says.
Charlotte’s attention later turned to the leading causes of clogged pipes: grease and tree roots. The utility inspects restaurants to make sure grease doesn’t go down drains. It enlarged its fleet of trucks equipped with suction and water jets to clear pipes from nine to 15.
“For the miles of line they have, they do a good-enough job,” said Catawba Riverkeeper Sam Perkins, the watchdog of local waters.
Homegrown technology played a part in the turnaround.
A decade ago, the utility and UNC Charlotte engineers began searching for new ways to keep sewers flowing. UNCC electrical engineer Ivan Howitt had an idea: Use sound waves to “listen” for pipeline blockages.
That would mean the utility could clean only pipes that really need it, saving time and money for cleaning that costs more than $10,000 a mile.
Howitt’s brainchild, dubbed Sewer Line Rapid Assessment Tool or SL-RAT, eventually went commercial.
He’s now founder and chief technology officer of a Charlotte company, InfoSense, that sells SL-RAT throughout the U.S. and in Australia, South Africa and Canada.
“Early on in the days when I wasn’t making any salary, the reason for my doing that was the ability to see something I had developed being used in helping solve a problem,” Howitt said.
The device soon proved its worth. When the Democratic National Convention came to town in 2012, the utility saved $225,000 by first screening uptown sewers instead of cleaning them all as a precaution against backups.
Charlotte Water tested 1.2 million feet of pipe this year and found that only 14 percent of the lines needed cleaning or closer inspection.
For the miles of line they have, they do a good-enough job.
Catawba Riverkeeper Sam Perkins
“It allows us to be more strategic,” said utility operations chief Angela Lee. “What the SL-RAT does for us is say, from this manhole to that manhole, this area looks good.”
The utility has deployed or is testing other new tools. One two-foot device records video as it’s propelled by water jets through sewer pipes. Another, a sensor mounted under manhole covers, monitors pipeline flows to detect problems.
Housing complexes a problem
Rusty Rozzelle, Mecklenburg County’s longtime water quality chief, has witnessed Charlotte Water’s improved spill performance.
“The utility, based on the numbers and what we see, is doing better than it ever has,” he said.
Rozzelle’s staff, which monitors the health of local waters, issues don’t-swim advisories when sewage reaches lakes. It has issued two advisories so far this year and four in 2014.
A growing problem, Rozzelle said, is privately owned sewer lines at multifamily complexes such as apartments. Charlotte Water has no responsibility for maintaining the lines, and complex owners might not know they’re supposed to until problems erupt.
The result is spills from grease-clogged lines or failing joints: 49 since 2011. Rozzelle’s staff created a program to educate complex owners about sewer line maintenance.
Harder to parse is the overall impact sewage spills have on local waters.
Sophisticated new tests, of DNA and antibiotic resistance, can detect the sources of bacteria that have for years plagued many Mecklenburg County creeks. In the three creeks sampled so far, more bacteria had come from dogs, deer and raccoons than from humans.
Mecklenburg creeks, meanwhile, are slowly recovering their health.
The county began prohibiting development of streamside zones that soak up pollutants including bacteria in the late 1990s. In 1996, 25 percent of major stream miles were safe for human contact. This year the number is 76 percent.
How Charlotte compares
Spills reported to North Carolina
Miles of line
Gallons to surface water
Source: N.C. Department of Environment and Natural Resources