Storage Facility

What is the Granite Bridge storage facility and where would it be located?


The Granite Bridge storage facility would consist of a liquefied natural gas (LNG) storage tank and other ancillary buildings, located on a 140 acre parcel, west of Exit 6, adjacent to Route 101 in Epping. The facility would liquefy and store natural gas, until it is needed by the residents and businesses of New Hampshire. When needed, the natural gas will be returned to its normal state and placed back into the pipeline. Purchasing natural gas when prices are low and then storing it and using it when prices are high would save our customers money and increase reliability. This facility would connect to the Granite Bridge pipeline, located within the New Hampshire Department of Transportation (NHDOT) right-of-way along Route 101, a designated state Energy Infrastructure Corridor.




What is LNG?


LNG, or liquefied natural gas, is natural gas in liquid form. When natural gas is cooled to -260°F it turns into a liquid. As a liquid, LNG is 1/600th the volume of natural gas vapor, which allows large amounts of natural gas to be stored in specially designed tanks. LNG is not explosive or flammable in its liquid state. LNG is widely used across the country, particularly in the Northeast and New England by natural gas distribution companies, like Liberty Utilities, to serve their customers primarily during peak winter periods.




Would the Granite Bridge storage facility be safe?


Yes. The safety of our customers, employees and the public is our highest priority and a core value of Liberty Utilities. Properly constructed and maintained LNG storage facilities have excellent safety track records. Design and construction is strictly regulated and the monitoring of proper maintenance is overseen by the New Hampshire Public Utilities Commission (NH PUC) and the U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration (PHMSA). LNG has been safely used and transported for over 70 years. LNG is not explosive or flammable in its liquid state. If exposed to the environment, LNG would rapidly warm to its gaseous state and evaporate, leaving no residue on water or soil. The LNG storage facility would have several layers of safety systems to prevent and contain a release of liquid or vapor. These include a full containment LNG storage tank system, additional LNG impoundment areas, temperature, vapor and fire sensors that would automatically activate on-site fire protection systems, as well as alerting facility personnel of the precise area where the detection originated. In addition, the LNG storage facility would be staffed 24 hours a day, seven days a week and monitored and controlled by an on-site control center and remotely by our System Control Center, located in Londonderry, NH. We will also work closely with local emergency management personnel on the development of safety procedures for the operation of the facility.




What are the components of the LNG storage facility?


The LNG storage facility would consist of several buildings, located on approximately 15 acres, within the 140 acre property adjacent to Route 101 in Epping. At the site there would be a full containment LNG storage tank system. A full containment tank system is comprised of an inner-tank made of nickel-steel, which is specially designed to contain the cold liquid. This inner tank would be surrounded by a second layer of containment, designed to hold the entire contents of the inner tank, effectively functioning as an outer tank in the unlikely case the inner tank were to release LNG. The tank would be constructed on-site. In addition to the full containment storage tank system, there would be buildings housing the equipment which would cool the natural gas to its liquid state and then warm the natural gas to convert it back into a gaseous state when additional supply is needed. We would also have an on-site control center, where our employees would monitor and operate the facility, as well as backup power generators, which would ensure continued operation in the event of a power outage. On-site there would also be a building to house the compression equipment, which would be used to compress the natural gas before it is reintroduced to the Granite Bridge pipeline. The compression equipment would run on electricity and not generate any emissions. Finally, there would be pretreatment equipment, which will clean the natural gas of any impurities, such as trace amounts of propane and ethane, before it is liquefied.




How big would the storage facility / LNG tank be?


The entire storage facility footprint would be approximately 15 acres, located within the 140 acre site. The LNG storage tank would be able to store up to 2 billion cubic feet (BCF) of LNG and would be between 150 to 170 feet high and approximately 200 feet in diameter.




How was the location for the storage facility selected?


We reviewed many potential locations along the Route 101 Energy Infrastructure Corridor for the LNG storage facility. The site in Epping, which is presently an abandoned quarry, was selected because of its proximity to the highway, the size of the parcel and natural topography. Because the location was previously excavated during quarry operations, it provides the opportunity to construct the storage tank approximately 30 feet below grade, thereby reducing its visual impact.




What is a full-containment LNG storage tank?


There are several different types of LNG storage tanks. Single, double and full containment storage tanks all meet federal safety requirements and have different characteristics. For the LNG storage facility in Epping, we chose the most robust tank design, known as a full containment tank system. A full containment LNG storage tank system is comprised of a free standing inner tank designed to hold the full liquid capacity of the LNG, surrounded by a second free standing tank, also designed to hold the entire liquid capacity of the inner tank. Essentially, a full containment storage tank system is a tank housed within another tank. This ensures the highest level of safety and adds an additional layer of complete containment, in the unlikely event of an LNG release.




What would happen if there was a release of LNG?


We took great care in designing the LNG storage facility to protect against the possibility of an LNG release. In the unlikely event that the LNG storage tank began to leak, the second free-standing storage tank that surrounds the inner tank is designed to capture and hold the entire contents of the inner tank. In addition, the tank would sit at the bottom of the excavated quarry, which would act as an addition level of partial containment. All piping and external equipment would have specially designed impoundment systems to collect and contain leaks. Once exposed to the environment, the LNG would rapidly warm to its gaseous state and evaporate, leaving no residue on water or soil. It is important to note that the LNG contained within the storage tank is not stored under high pressure, with pressure in the tank typically less than 2 psi. In addition to the full containment storage tank system design and impoundment areas, the LNG storage facility would have several layers of safety systems in place to mitigate a release. These include temperature, vapor and fire sensors that would automatically activate on-site fire equipment. The Granite Bridge storage facility would be staffed 24 hours a day, seven days a week and monitored and controlled on-site and remotely by our System Control Center, located in Londonderry.




Would there be truck traffic to and from the LNG storage facility?


Once constructed, truck traffic in and out of the facility would be be minimal. The LNG storage facility is designed to serve our customers in New Hampshire through the Granite Bridge pipeline, which would be located within the NHDOT right-of-way, along Route 101. When needed by our customers in the winter, the LNG would be warmed back to its original gaseous state and placed back into the pipeline. Because the Granite Bridge LNG facility would be capable of liquefying natural gas from the Granite Bridge pipeline and storing it, truck deliveries would not be required to fill the tank. Some of the liquid stored at the Granite Bridge LNG facility would be transported to service our existing facilities throughout the year. The Granite Bridge LNG storage facility would reduce the number of truck deliveries to those facilities, located in Tilton, Concord and Manchester, from upwards of 200 to approximately 20 annually.




Would the Granite Bridge storage facility be monitored?


The LNG storage facility would be staffed by Liberty Utilities employees 24 hours a day, seven days a week. In addition, the facility would be monitored and controlled on-site and remotely by Liberty Utilities’ System Control Center, which is located at our offices in Londonderry, NH.




Would the LNG storage facility produce any emissions?


When the LNG storage facility is operating there would be minimal emissions associated with heating the propylene glycol, which is used to warm the LNG during the cold months. Propylene glycol is non-toxic fluid used in food, medicine and cosmetics. There would also be some minimal air emissions associated with operating the emergency generator periodically for testing. Any air emissions would be regulated by the New Hampshire Department of Environmental Services (NHDES).




Would the storage facility make any noise?


Yes, but noise-generating equipment like compressors needed to move and cool the natural gas would be housed in insulated building structures to prevent the noise from impacting the public. We would adhere to strict federal and state regulations regarding the level of noise allowed at the facility property line.




Would there be compressors located at the storage facility? How big would they be and would they make any noise or produce any emissions?


There would be three compressors located at the LNG storage facility. One refrigerant compressor that would be used to compress and cool nitrogen as part of the process of turning the natural gas into a liquid. Two other compressors, a primary and a back-up, would be used to pressurize natural gas when it is added back onto the Granite Bridge pipeline. The refrigerant compressor would use a similar process to an air conditioning system, which compresses a refrigerant to create a cooling effect. At the facility the refrigerant compressor would be compressing nitrogen. This compressor would not be used to compress or move the natural gas. The refrigerant compressor would be sized between 9,000 and 12,000 horsepower and would be powered by electricity, instead of natural gas or propane, and would not generate any emissions. The other two compressors, one primary and one back-up, would be needed to pressurize the natural gas when it is being placed back onto the Granite Bridge pipeline. Each of these compressors would be approximately 500 horsepower, and would also be powered by electricity, instead of natural gas or propane, and would not generate any emissions. All compression equipment would be housed in insulated building structures specially designed to prevent the noise and vibration from impacting the public. We would adhere to strict federal and state regulations regarding the level of noise allowed at the facility property line.




Are there any other LNG storage facilities in New England?


Yes. There are currently 43 LNG facilities located in 28 towns serving customers in New England.

The closest field erected storage tank, similar to the proposed Granite Bridge storage facility, is located in Tewksbury, Massachusetts. The only other full containment LNG storage facility is located in Waterbury, Connecticut. The closest 2 BCF LNG storage tank is located in Everett, Massachusetts, just north of downtown Boston.

In New Hampshire there are three LNG storage facilities, located in Manchester, Tilton and Concord. These facilities have been providing safe and reliable service to our customers for 45 years.

At present, there are 113 LNG facilities located in the United States.




How would the Granite Bridge storage facility be secured?


Site security is of critical importance to maintaining a safe facility. The Granite Bridge storage facility would comply with strict federal regulations requiring site security procedures and measures. These measures include numerous layers of security, including controlled access points, redundant security fencing, security lighting, motion detection, video monitoring and trespass alarms.

Trained Liberty Utilities’ employees would be at the LNG storage facility 24 hours a day, seven days a week. In addition, the facility would be monitored and controlled on-site and remotely by Liberty Utilities’ System Control Center, which is located at our offices in Londonderry, NH.

All our safety systems are regularly monitored and tested. We would work closely with state, local and federal agencies to ensure we coordinate and communicate effectively in all aspects of Granite Bridge’s safety systems, this includes inspections and safety drills.




What would happen to the storage facility if there was an earthquake?


The LNG tank and storage facility is being designed to withstand a magnitude 6.3 earthquake without a release. This magnitude earthquake is estimated to occur once every 2,475 years in the Epping-area, based on information provided by the United States Geological Survey. According to a report by the National Association of State Fire Marshals: “No LNG storage tank failures have ever occurred due to seismic activity. This is true even in Japan, which is one of the most seismically active areas in the world.”




Would the LNG storage facility smell?


No. Natural gas is odorless. The rotten egg smell that is associated with natural gas and propane comes from an additive called mercaptan. Mercaptan is a non-toxic chemical added to make a natural gas leak detectable before it creates a hazardous situation. Mercaptan and trace amounts of propane, ethane and butane, which are present in natural gas, need to be removed as part of the process to cool natural gas to -260°F. Once natural gas is in its cryogenic liquid form, it is odorless. On-site equipment would monitor and detect any accidental releases. The mercpatan and the gases that were removed prior to the cooling process are piped back into the natural gas that leaves the storage facility, which is used to serve our customers in New Hampshire. The normal operation of an LNG storage facility does not generate detectable odors. Liberty Utilities operates three LNG storage facilities in Manchester, Concord and Tilton. At these facilities mercaptan is added to the natural gas before it placed into our distribution system to serve customers. There is no odor at these facilities.





For a visual representation of the tank from surrounding areas, click here.

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