Your Gas Delivery System
Natural gas is found in deep underground reservoirs and requires a well to be drilled in order to reach it. Once a drill discovers a reservoir, the gas is brought to the surface through pipes. Some of this gas is stored in liquid form for future use by compressing it under high pressure. The remainder of the gas, though, is sent to other regions via transmission pipelines, such as Unitil’s Granite State Transmission pipeline. (Here is a link to the pipeline operators in your area.)
Local distribution companies are supplied via these transmission pipelines. The local gas distribution system is connected to a transmission pipeline at a meter station or city gate. The city gate has two purposes: to measure the gas supplied and to control the gas pressure. The transmission company measures the amount of gas flowing into the city gate. The local distribution company reduces the pressure of the gas from the transmission pipeline to match the pressure of its distribution system.
The distribution system is composed primarily of two types of pipelines: mains and services. Mains receive the gas from the city gate and distribute it through the supplied area. Service pipelines carry gas from the main and supply the customer after passing through a meter. As it travels through the distribution system, the gas pressure is controlled by regulators - a special type of valve. Regulators can reduce the gas pressure, if needed, or if the gas pressure increases above a set limit, regulators can also shut-off gas flow.
To better regulate a distribution system’s gas pressure and stabilize gas pricing (i.e., peak shaving), local distribution companies use liquefied natural gas (LNG) stations and liquefied petroleum gas (LPG) -air plants. An LNG station draws natural gas from the distribution system and temporarily stores it under high pressure in liquid form. The gas is then reintroduced into to the distribution system by vaporization for future use.
An LPG-air plant stores liquefied petroleum gas supplied by a third-party vendor. When needed, the LPG is mixed with air for introduction into the distribution system. This mixing is needed to ensure that the gas properties throughout the distribution system remain uniform. The ability to purchase LPG in smaller quantities allows the local distribution company to make detailed system corrections more frequently – allowing for a consistent gas supply to the customer.
Natural gas pipelines are sometimes identified by markers placed at intervals along pipeline rights of way. Markers display 24-hour emergency telephone numbers and might provide other identifying information. Pipeline markers are important to your safety. It’s a federal crime to willfully deface, damage, remove or destroy any pipeline sign or right-of-way marker.
While the markers aid in identifying the presence of pipelines in the area, they don’t show the exact location, depth, or how many pipelines are in the right-of-way. Don’t rely solely on the presence or absence of a pipeline marker to determine whether or not a pipeline is buried below. Always call Dig Safe ® at 811 or 888-344-7233 to have underground pipelines marked.
Rights of Way
A pipeline right-of-way is the strip of land above and around a pipeline. Rights-of-way are kept clear of obstructions and vegetation to enable Unitil to safely operate, patrol, inspect, maintain and repair its pipelines. We regularly inspect our rights-of-ways.
A right-of-way agreement between Unitil and the property owner is called an easement. Easements provide us with permanent, limited interest to the land to enable us to access, operate, test, inspect, maintain and protect our pipelines for your safety. Although agreements may vary, rights-of-way usually extend up to 25 feet each way from the center of the pipeline.
If Unitil has an easement on your property, you should be aware of our guidelines for encroachment and construction near natural gas pipeline equipment. It’s important that property owners not install any structures, store anything that could be an obstruction, or plant trees or shrubs along the right-of-way. Normal gardening and agricultural activities (e.g., lawns) are generally acceptable. But you should never dig or construct anything in the right-of-way without first having a Unitil representative mark the pipeline, stake the right-of-way and walk you through our construction guidelines.
Our Goal is a Safe System
Natural gas systems have a proven record of safety, but incidents can occur. Hazards include blowing gas, line rupture, fire, explosion, or possible asphyxiation. We care about your well being and work hard to make our system safe.
Our gas control and dispatch center operates 24 hours a day, seven days a week. We regularly patrol our pipeline rights-of-way and conduct regular inspections of our pipeline system. Our gas operations employees receive regular training and are qualified under U.S. Department of Transportation standards as natural gas pipeline operators.
Employees are on-call at all times to respond to any contingency. We spend millions of dollars annually in pipeline replacements and upgrades. In addition, we work with emergency responders to make them aware of our pipelines and how to respond in an emergency.
In accordance with federal regulations, some segments along the pipeline have been designated as High Consequence Areas. We have developed supplemental assessments and prevention plans for these highly-populated areas with transmission pipelines traversing them. Here is a link outlining Unitil's plan and activities to ensure the safety of our pipeline system. It is a summary of our Integrity Management Plan.
For more information on gas safety in the community, please contact us at 866-933-3821888-301-7700866-933-3820.