Officials say the pop-pop-popping of water mains here over the past several days is a typical winter phenomenon and not indicative that our delivery systems are falling apart beneath us.
If anything, the number of breaks is decreasing, thanks to milder weather and millions of dollars invested in replacing pipes, according to representatives of the two largest local providers, Pennsylvania American Water and the Pittsburgh Water and Sewer Authority.
Penn American has spent more than $200 million on system improvements in the Pittsburgh district in the past two years and installed 53 miles of new pipe in its network of approximately 1,500 miles, spokesman Gary Lobaugh said.
Last year saw a 20 percent reduction in leak repairs, he said. "I think we're starting to see the fruits of our investment."
The Pittsburgh authority doubled its capital spending on items like water and sewer lines and treatment plant upgrades from 2009 to 2010, and has spent an average of $30 million per year over the last four years, spokeswoman Melissa Rubin said.
"We're not experiencing more leaks than normal," she said. "It just happens that we had two in high-traffic areas."
The authority repaired 44 leaks in December, down from 48 in December 2011 and 83 in December 2010. Part of the decline may be weather-related -- average monthly temperatures the past two Decembers were 12 to 13 degrees warmer than in 2010.
A rapid drop in temperatures that began last week caused several high-visibility pipe failures, including one in Downtown that drenched the Parkway East and closed a major intersection and parking facility for four days.
Crews late Sunday completed repairs at Fort Pitt Boulevard and Wood Street, where a 12-inch main burst and sent water cascading into the "bathtub" section of the inbound parkway. The incident early Thursday damaged a gas main and caused closure of the intersection and the only entrance to the Monongahela Wharf.
On Saturday morning, a 30-inch main under the South Millvale Avenue Bridge in Bloomfield ruptured, disrupting service on the Port Authority's Martin Luther King Jr. East Busway and forcing Children's Hospital of Pittsburgh of UPMC to switch to an alternate water supply. Mains also gave out on Joan Drive in North Versailles and Woodstock Avenue in Swissvale.
There was more Monday: A line broke at Penn and North Braddock avenues in North Point Breeze at about 1 a.m. A 10-inch main burst on Route 51 in Overbrook, flooding an inbound lane and tying up traffic. A break also was reported on Brookline Boulevard near Glenarm Avenue.
The district is about to get a respite from the subfreezing weather, at least during the daytime, according to the National Weather Service. It forecasts highs in the 40s today through Thursday and in the 50s Friday through Sunday.
Much of the region's water infrastructure is 70 to 100 years old and is cast iron pipe, which is the material considered by water suppliers as most likely to fail, according to a Utah State University study.
"Cast iron, being very brittle, will snap like a pretzel stick" under excess pressure, said Anthony Emanuele, superintendent of field operations for Penn American. The pressure can come from saturated soil expanding in freezing weather and from the water inside the pipes, which gets denser when it's cold.
Problems typically start when river temperatures fall to 38 degrees, he said. According to the U.S. Geological Survey, water temperatures Monday on the Allegheny and Monongahela rivers, from which Pittsburgh and Penn American draw their supplies, ranged from 33 to 37.5 degrees.
Utilities in the 1970s began using a more flexible ductile iron pipe that is lined with concrete to prevent corrosion and sealed at the joints with rubber rather than lead. But most of the lines throughout the Northeast are still the older cast iron variety.
Experts for several years have warned about the deteriorating shape of the nation's water delivery systems. According to the U.S. Environmental Protection Agency, there are more than 240,000 water main failures each year, and it has projected a $500 billion gap in funding that will be needed to maintain water infrastructure by 2020.
In a 2009 "report card" on the nation's infrastructure, the American Society of Civil Engineers gave a D-minus grade to the condition of U.S. drinking water systems.
An industry group, Uni-Bell PVC Pipe Association, says 850 water main breaks occur every day in North America, at an annual repair cost of $3 billion. It maintains a running Water Main Break Clock on the Internet.
A study for the American Water Works Association last year estimated a need to spend $1 trillion by 2035 on replacing worn-out water mains and installing new ones to serve growing populations.
A report prepared for the Pittsburgh authority said billions of dollars will be needed over the coming 40 years to upgrade its infrastructure, Ms. Rubin said.
"Certainly we would like to spend more. We'd like to replace pipes when they're 80 years old and not have 100-year-old pipes. We have to balance our needs with what our customers can afford," she said. "We have aging infrastructure and a declining population."