Feb 20, 2009 2:54 pm US/Eastern
Explainer: How Natural Gas Gets To Your Home
BOSTON (WBZ) ―
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Massachusetts has an extensive underground gas delivery system that serves nearly 1.5 million gas customers across the state.
Before it gets to your home, natural gas passes through large transmission lines, then into gas mains, and finally into service lines that feed your home.
TRANSMISSION LINES
According to the state Department of Public Utilities, there are 1,000 miles of gas transmission lines across the state. Those lines are 12 and 24 inches in diameter and are owned by three companies, Algonquin Gas Transmission Co., Tennessee Gas Pipeline Co., and Northeast Pipelines Co.
GAS MAINS
Utilities, like New England Gas, then tap into those transmission lines through gas mains. There are 19,000 miles of gas mains in Massachusetts operated by seven local distribution companies and four municipal gas departments:
Bay State Gas
Blackstone Gas Company
New England Gas Company
National Grid
Berkshire Gas Company
Commonwealth Gas Company (NSTAR)
Fitchburg Gas and Electric Light Co (Unitil)
City of Holyoke Gas and Electric Department
Middleborough Gas and Electric Department
Westfield Gas and Electric Light Department
Wakefield Municipal Gas and Light Department
Gas mains are normally two inches or 16 inches in diameter and made of steel, plastic or cast iron.
SERVICE LINES
Service lines run from those 19,000 miles of gas mains, into homes and businesses across the Commonwealth. The service lines are between ½ inch and 1 ½ inches in diameter and made of steel or plastic. There are approximately 1.4 million service pipelines running into Massachusetts buildings.
GAS LINE INSPECTIONS
So who inspects all of those lines? That is left up to the gas companies, which in turn report back to state engineers.
Federal law requires that gas companies conduct regular leak surveys, though the frequency varies by location. A leak survey is required once a year in a business district, but only once every three to five years in a residential neighborhood.
If there is a call reporting a gas odor or possible leak, companies are required by law to respond within one hour. The most recent data available for Massachusetts, from 2007, showed that all gas companies met those requirements.
Read: What to do if you smell natural gas
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