Failing Infrastructure-Urban Gas Lines Edition

Live Science, via nc links:

Beneath the streets of Boston is an aging network of natural gas pipelines that delivers fuel to heat homes and power appliances but also threatens to feed fires and even cause explosions. Highlighting the need for repairs, a new study detected more than 3,300 natural gas leaks throughout the city.
Researchers from Boston University and Duke logged 785 road miles (1,263 kilometers) in the city, driving around in a GPS-equipped car with a device to measure methane, the chief chemical component of natural gas. The team discovered 3,356 separate natural gas leaks — some of them potentially hazardous.
"While our study was not intended to assess explosion risks, we came across six locations in Boston where gas concentrations exceeded the threshold above which explosions can occur," Nathan Phillips, associate professor at BU, said in a statement.
The leaks were associated with old cast-iron underground pipes and were distributed evenly across all neighborhoods, regardless of socioeconomic differences, the researchers said. Their findings were detailed online this week in the journal Environmental Pollution.
Concerns about aging natural gas pipelines aren't unique to Boston. Each year, pipeline failures cause an average of 17 deaths, 68 injuries, and $133 million in property damage across the nation, according to the U.S. Pipeline and Hazardous Materials Safety Administration. Some of the devastating fires that erupted in the New York area during Hurricane Sandy were fueled by natural gas and recent deadly accidents — like the 2010 explosion in San Bruno, Calif., which killed eight — have drawn attention to the importance of pipeline safety. Natural gas leaks also pose an environmental risk, as methane is a greenhouse gas.

One good thing is that at least they added odorant to the gas so it is easier to detect leaks.  That wasn't always the case:

The New London School explosion occurred on March 18, 1937, when a natural gas leak caused an explosion, destroying the London School of New London, Texas, a community in Rusk County previously known as "London". The disaster killed 425 students and teachers, making it the worst catastrophe to take place in a U.S. school building. In the mid-1930s, the Great Depression was in full swing, but the London school district was one of the richest in America. A 1930 oil find in Rusk County had boosted the local economy, and educational spending grew with it. The London School, a large structure of steel and concrete, was constructed in 1932 at a cost of $1 million (approx $15.75 million in 2009 dollars). The London Wildcats (a play on the term "wildcatter", for an oil prospector) played football in the first stadium in the state to have electric lights.
The school was built on sloping ground, and a large dead-air space was contained beneath the structure. The school board had overridden the original architect's plans for a boiler and steam distribution system, instead opting to install 72 gas heaters throughout the building.
Early in 1937, the school board canceled their natural gas contract and had plumbers install a tap into Parade Gasoline Company's residue gas line in order to save money. This practice, while not explicitly authorized by local oil companies, was widespread in the area. The natural gas extracted with the oil was seen as a waste product and was flared off. As there was no value to the natural gas, the oil companies turned a blind eye. This "raw" or "wet" gas varied in quality from day to day, even from hour to hour.
Untreated natural gas is both odorless and colorless, so leaks are difficult to detect and may go unnoticed. Gas had been leaking from the residue line tap, and built up inside an enclosed crawlspace that ran the entire 253-foot (77 m) length of the building's facade. Students had been complaining of headaches for some time, but little attention had been paid to it.
March 18th was a Thursday. Friday's classes had been canceled to allow for students to participate in the neighboring city of Henderson's Interscholastic Meet, a scholastic and athletic competition. Following the school's normal schedule, first through fourth grade students had been let out early. A PTA meeting was being held in the gymnasium, a separate structure roughly 100 feet (30 m) from the main building. 

At some time between 3:05 and 3:20PM Central (local) time, Lemmie R. Butler (an "instructor of manual training") turned on an electric sander. It is believed that the sander's switch caused a spark that ignited the gas-air mixture.

Reports from witnesses state that the walls of the school bulged, the roof lifted from the building, and then crashed back down and the main wing of the structure collapsed. The force of the explosion was so great that a two-ton concrete block was thrown clear of the building and crushed a 1936 Chevrolet parked nearby.
Estimates of the number dead vary from 296 to 319, but that number could be much higher, as many of the residents of New London at the time were transient oilfield workers, and there is no way to determine for certain how many of these roughnecks collected the bodies of their children in the days following the disaster, and returned them to their respective homes for burial. Approximately 600 students and 40 teachers were in the building at the time; only about 130 escaped without serious injury.
Experts from the United States Bureau of Mines concluded that the connection to the residue gas line was faulty. The connection had allowed gas to leak into the school, and since natural gas is invisible and is odorless, the leak was unnoticed. To reduce the damage of future leaks, the Texas Legislature began mandating within weeks of the explosion that thiols (mercaptans) be added to natural gas. The strong odor of many thiols makes leaks quickly detectable. The practice quickly spread worldwide.
Shortly after the disaster, the Texas Legislature met in emergency session and enacted the Engineering Registration Act (now rewritten as the Texas Engineering Practice Act). Public pressure was on the government to regulate the practice of engineering due to the faulty installation of the natural gas connection; Carolyn Jones, a nine year old survivor, spoke to the Texas Legislature about the importance of safety in schools. The use of the title "engineer" in Texas remains legally restricted to those who have been professionally certified by the state to practice engineering.