Systemic Gas Delivery System Failure

[hpinson]

Trying to understand the massive systemic gas delivery failure in the Merrimac Valley of MA yesterday.

If I am understanding, the system employed a low-pressure delivery method, that when over-pressured, simply allowed unregulated gas to flow out of any open oraface - like a pilot in an appliance, and the result was either a shooting flame or just free-flowing gas into a building.

Somehow a high pressure gas source got connected to a regional low-pressure unregulated delivery system.

I.e., homes did not have local regulators on their gas supply.

Am I understanding that right?

Why on earth would code allow unregulated gas delivery systems? Some of the homes affected seemed relatively recent too. I am told by a friend who lives near there that Andover is a rather affluent city.

[Danfish]

While I do not have first hand knowledge of this particular gas distribution system, from what I read this is mostly cast iron piping... what we called in the industry a "low pressure" system.  Such systems normally operate in the pressure range of 7 to 14 inch of water column, about 1/4 pound.  This low delivery pressure requires no pressure regulator at the service entrance.  Most distribution systems today operate in the 50 pound range and do require a house regulator to reduce the pressure to 7 inches W.C.  All distribution systems require a district regulator station to reduce pressure from the principal source.  Properly designed district regulator stations have over pressure protection to prevent over pressure of the downstream; however, these stations usually have bypass piping that can be used during maintenance.  Use of the bypass requires manual monitoring of the downstream pressure.

A vast majority of gas distribution companies have done a way with low pressure systems, which were a product of the old "manufactured" gas days.

[MountainDon]

Apparently, some of the piping there  dates from as long ago as 1860.  Hard to believe.

[hpinson]

Wow. I'm surprised this is even allowed in public infrastructure and code requirements. Apparently it is though. It must be such a massive systemic problem that it is unaddressable as public policy.

[Dave Sparks]

The owner of the system has had explosions 3 other times?  Picked the wrong place to live in the big city I guess.

[hpinson]

Andover MA is affluent outer suburbs and some of the homes that had explosions were surprisingly new. Lawrence MA however is one of the poorer towns in the state and I can imagine gas delivery infrastructure that is ancient. It's inexplicable to me that at town like Andover, that has the tax base, was still so entrenched in this antiquated system.

[rich2Vermont]

As a resident of Andover for the last 30 years (until we move up to Vermont next year) we are directly affected. Thankfully, our house was a couple of miles from the hardest hit areas. Nevertheless, we got a reverse-911 call to turn off our gas and evacuate. We did, eventually. Of all the things we've dealt with over the years -- hurricanes, ice storms, microbursts, etc., this was the weirdest. Massachusetts has the oldest gas delivery system in the nation. To their credit, Columbia Gas has been working to replace lines for years. Our street was done a few years ago. Not to their credit, they were awful in handling this situation. While the actual cause hasn't been determined, the prevailing opinion is there was a valve failure between the high-pressure pipeline and the low-pressure delivery system. NTSB is on the ground investigating, but it'll be months before we know for sure. Meanwhile, each street and house needs to be cleared by police, fire, and gas people. Our street is clear for reentry, but the street 3 houses away has not been, yet. Then there's an involved process to get the gas turned on again. They say it'll be weeks. So, no hot water, heat, stovetop, dryer for awhile. But, given that we still have a house, it could have been far worse. It's truly amazing only one person died. Amazing credit to the local responders -- 35 houses in Andover with fires within an hour. Crazy. Oh, and regarding the nature of affluent town and antiquated systems, if you lived here you'd understand how ridiculous it is that so many residents scream about taxes while also complaining about these systems (our taxes are relatively low). I've heard we have water pipes over 100 years old. But to do anything remotely progressive in this town takes forever. It took eight years to build a dog park, and that only happened when it was privately funded. That attitude is one I will not miss when we leave.

[Don_P]

When I was a kid they replaced a wooden water main in Boston. In Raleigh, NC we were also on town gas in the old part of town. We don't want to pay for infrastructure in this country.

[Dave Sparks]

Out west we spend all the infrastructure money on social problems and when there is none left things go bad. That is the nice part of living offgrid. The buck stops with guy and gal who live here