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Nicor Storage Facility
Nicor Storage Facility

Underground Storage

Providing Natural Gas When We Need It Most

Keeping natural gas safe, affordable and reliable is our focus at Nicor every day. Our team of experts works to purchase natural gas when it is most cost effective and store it for later use. This system of buying and storing natural gas allows us to serve 2.2 million customers in Illinois.

For over six decades, Nicor Gas has used underground storage facilities to safely store billions of cubic feet of natural gas across eight underground storage fields throughout the state.

During the 2019 Polar Vortex, Nicor delivered more than 4.8 billion cubic feet of natural gas, and no one lost heat due to curtailment. These incredible engineering feats are only possible through the use of storage facilities.

Without these critical reserves, it would be impossible to continue providing clean, safe, reliable and affordable natural gas to those who depend on it year-round.

Nicor Storage Facility

What is an Underground Storage Facility and How Does it Work?

An underground aquifer reservoir is a natural underground formation made of porous sandstone layers covered by a solid dome-shaped caprock. These underground storage facilities are a safe and widespread practice. The United States Energy Information Administration reports that throughout the U.S. there are 388 such facilities ready to meet demand. Through wells, natural gas is injected into the reservoir, making the gas available for withdrawal later.

Gas must be at higher pressures than the transmission pipeline for it to flow into the system. At some fields, the gas is already at that higher pressure. At others, gas must be pumped into the transmission line. The gas must be dehydrated before it starts being distributed.

There are two kinds of gas in the aquifer:

  • Base gas – a cushion for working storage gas that supports reservoir pressure
  • Working gas – gas available for withdrawal


Nicor Gas takes seriously the commitment to safely storing and delivering natural gas. We manage our facilities with the highest of integrity and transparency, employing dedicated teams of experts in the storage and maintenance of natural gas and working with multiple regulatory bodies.

Each one of our storage facilities receives oversight, audits and inspections from the Occupational Safety and Health Administration (OSHA), Illinois Department of Natural Resources (IDNR), Illinois Environmental Protection Agency (IEPA), Illinois Commerce Commission (ICC) and from the United States Pipeline and Hazardous Materials Safety Administration, which establishes national policy and sets and enforces standards for facilities and pipelines.

We maintain a secondary capture system to prevent gas from rising to the surface and continue to make enhancements and upgrades to our infrastucture to ensure we have up-to-date measures in place to protect the communities we serve.

Nicor’s History Storing Natural Gas

When Nicor first started storing gas, it was in low-pressure, above-ground tanks and interconnected high-pressure cylinders buried under the surface of the soil. Then, in 1954, a pipeline supplier developed the state's first underground facility. Called an aquifer, it was located near Herscher, southwest of Kankakee.

Nicor shared some of Herscher's storage capacity, but as customers grew, we decided we needed our own storage fields.

In 1957, we found the potential for storage capabilities in Illinois. After conducting tests and determining that the location was prime for a storage facility, the first cubic foot of gas was injected in 1958. Our goal was to provide reserves for the 1960-61 heating season. As our customer base and service territory grew, we continued to develop new storage fields.


How much natural gas in stored in facilities across Illinois each year?

Nicor Gas has about 150 billion cubic feet of annual storage capacity across eight underground storage aquifers: Troy Grove, Ancona, Pontiac-Mt. Simon, Pontiac-Galesville, Lake Bloomington, Hudson, Lexington and Pecatonica

How much does storage support your winter delivery?

Storage supplies one-third of our normal winter deliveries. In 2019 during the Polar Vortex, a record setting 4.8 billion cubic feet of natural gas was supplied to customers in a single day to heat their homes and support them through the extreme weather event. Without the natural gas in storage, more than 825,000 customers would have been without heat during the dangerously cold temperatures.

Are underground aquifer storage facilities safe?

Yes. Nicor Gas is committed to ensuring the safety of our communities through continuous monitoring and improvements of our facilities. Our teams of dedicated experts in the storage and maintenance of natural gas work with regulatory committees to oversee the safety and transparency of our storage and maintenance of natural gas.

Does Nicor Gas operate the underground storage fields to profit from lower natural gas prices?

No. Our natural gas storage systems are a critical safety net to protect against price fluctuations in supply and demand for gas. We’re able to buy gas for customers when prices are typically lowest, store it for later use and pass those savings directly to our customers.