Plugging Leaks

With gizmos and grit, technicians detect leaks, protect labyrinth of water pipes under Boston


By David Abel   |  Globe Staff  |  
December 20, 2008 
As a cold rain slanted into his eyes, Mark Collins stood ankle-deep in a muddy puddle in a hole about 6 feet below ground. Just another day and another hole for a job that keeps him digging - and keeps the pipes of the city in good shape.
"The colder it is, the harder it is to dig," he said as he shoveled dirt and rocks this week in an effort to repair a leaky water pipe beneath a Roxbury sidewalk. "But someone's got to do it."
Every day, city residents use nearly 70 million gallons of water, which swishes through more than 1,000 miles of underground pipes. When one breaks, as occurred this week beside City Hall, hundreds of thousands of gallons of water seep into the ground and flood surrounding streets, damaging property and raising water costs for everyone in the city.
Over the past decade, as erosion and widespread construction have weakened aging pipes, city officials have poured $335 million into replacing and repairing the system. Part of the money has paid for the work of a crack squad of hole-digging, sound-detecting technicians such as Collins, who spend their shifts scouring the city for leaks and patching them to prevent breaks.
With the aid of technology - sophisticated sensors and computers have mostly replaced the old stethoscope-like devices that listened for leaks from the street - Boston has kept the number of water main breaks to significantly lower levels than similarly sized cities and helped conserve water.
As a result, city officials say, they have saved residents millions of dollars a year in costs.
"We purchase less water today than the system leaked" 30 years ago, said Thomas Bagley, deputy director of communications for the Boston Water and Sewer Commission. "Since 1977, there has been an 82 percent reduction in unaccounted-for water," or water lost to leaks.
In all, about 483 miles of water mains have been replaced or relined, he said.
So far this year, the city has had 35 water main breaks. The number of breaks - which officials say are more often the result of construction than age - has remained relatively constant, ranging in recent years from a low of 29 in 2005 to a high of 54 in 1995. The number of leaks discovered has fallen slightly over recent years, with 197 found in 2006 compared with 156 so far this year.
But the amount of water wasted from the leaks and breaks has fallen sharply. In 2005, the city lost 12 percent of an average 77.5 million gallons of water used daily; this year, the system has so far lost 7.9 percent of an average 68.5 million gallons of water used every day.
Tom Curtis, deputy executive director of the American Water Works Association, a Washington-based engineering society for water utilities, said Boston's 1,018 miles of water piping for its 600,000 residents compares favorably to other cities. On average, cities with more than 1,000 miles of pipes have 250 water main breaks a year.
For example, Washington, D.C., which has 1,300 miles of pipes serving 572,000 people, had 502 water main breaks last year. Officials in San Francisco, which has about 1,250 miles of pipes serving 750,000 people, said they average about 100 breaks a year. And in Fort Worth, where 3,300 miles of pipes provide water to more than a million people, there have been 263 water main breaks this year.
"The low breakage rate in Boston is not an accident," Curtis said. "Everyone in the water community considers Boston to have one of the best asset management programs."
City water officials are looking at how to use their new technology to make an even more substantial cut in the amount of water lost to leaks and breaks.
Over the last 20 years, the city has relied mainly on customer complaints to find leaks, and they have repaired or replaced an average of 17 miles of pipe a year based on where city work crews were repaving roads.
John Sullivan, chief engineer of Boston's Water and Sewer Commission, said the city now reads meters remotely, often multiple times a day; less than a decade ago, they could read the meters only every few months by sending a technician out.
They're also placing dozens of new sensors in downtown pipes, where most of the main breaks happen because of all the construction.
"With sophisticated mapping data, we can now find the most vulnerable pipes, take them out of the ground, send them to labs, and seek how much life is left in them - before there's a break or leak," Sullivan said.
But with all the jack-hammering and tunneling, main breaks are inevitable. For example, Sullivan suspects a recent project beside City Hall led to Wednesday's rupture of a high-pressure pipe for fire hydrants on Congress Street, which left hundreds of thousands of gallons flooding the area.
"The pipes rely on the soil being completely around them," he said. "Small disturbances in the soil can have big effects."
This week, as sheets of rain coated their hard hats, one of the city's leak-detection units prowled through downtown, Roxbury, and Dorchester for problems.
On Lincoln Street near Chinatown, Michael Campbell used a meat hook to open an iron water valve-box cover, lowered a DigiCorr Pro sensor several feet below the pavement, and walked back to a city van, where a radio signal sent a graphic display to a laptop computer.
He was listening for a high-pitched screaming sound or a telltale spike in the graphic. "The equipment's now so sensitive you can hear people talking [through the pipes], pick up radio stations, or hear people taking showers," Campbell said.
On this morning, with cars too closely streaming past, the team found no sign of a leak. So they packed up their gear and moved to the next location.
David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.