Natural Gas Safety
The systems that produce and transport natural gas can be hazardous when not handled properly. That’s why Dominion Energy takes extensive measures to minimize the risks presented by its infrastructure.
We go above and beyond the strong federal and state regulations for natural-gas pipelines.
We inspect and assess our transmission pipelines in many ways. Three particular ways are patrols, smart pigs and continuous monitoring by gas control. In addition to regular aerial observation and foot patrols, we also inspect pipelines from the inside, using sophisticated devices called smart pigs. These devices use computerized sensors capable of detecting and reporting anomalies such as dents and corrosion, enabling us to make appropriate repairs to ensure the integrity of the pipe. Dominion Energy uses smart pigs on more than half of its 8,000 miles of our transmission and storage system — well beyond regulatory requirements. Finally, pipelines are monitored around the clock from our Gas Control Command Centers.
We continuously monitor the pressure, temperature, and flow of gas through remote sensors placed along the entire length of a pipeline. Remote-controlled safety shutoff valves allow Gas Control operators to immediately shut off the flow of gas and isolate individual sections of pipeline if needed. Our redundant layers of protection for the Atlantic Coast Pipeline include steel pipe that is half an inch to three-quarters of an inch thick, covered with a corrosion-resistant epoxy layer. Before the ACP enters service, we will inspect every weld with ultrasonic testing and pressure-test the entire line to ensure both the pipe and the welds are secure.
Dominion Energy is committed to maintaining the integrity of its transmission pipeline system. To prevent external corrosion, we operate cathodic protection systems on our underground steel assets. In addition to annual monitoring at key locations, we perform detailed corrosion surveys for an average of 1,000 miles of transmission pipeline each year, to ensure these protection systems are functioning effectively. Internal corrosion is prevented through vigilant monitoring of constituents in the gas stream, evaluating potential impact to our assets, and applying targeted mitigative measures. We also examine the internal and external surfaces of our assets whenever operating and maintenance activities provide such opportunities, in order to validate the effectiveness of our programs.
Additional safety assessments for transmission and storage pipelines occur on both a cyclic and as-needed basis. These efforts help make serious incidents related to natural gas transmission and distribution in the United States rare.
This redundant system of vigilant monitoring enables us to detect and fix any problems in our system long before they present a hazard. We also have committed to expand the number of remote-controlled valves to lower response times even further.
Protecting the Public
But we know it’s not enough just to meet high safety standards. Over the past 20 years, third–party damage has been the primary cause of incidents on natural gas pipelines, accounting for about 25 percent of all serious incidents on transmission pipelines and about 33 percent on distribution pipelines.
So Dominion Energy also conducts public awareness programs to educate landowners near company facilities to help protect them and their communities. This is especially important along the 66,600 transmission and distribution miles of pipeline we operate across 11 states — Ohio, Pennsylvania, Maryland, New York, Virginia, North Carolina, West Virginia, Utah, Idaho, Wyoming and Colorado.
In order to protect our underground gas transmission pipelines from third-party damage, we are active in — and support laws requiring — the use of the 811 “Know what’s below; call before you dig” one-call system. Anyone planning to do work that disturbs the soil beneath streets, sidewalks, yards, farms, or other property is required to call the single designated number. All utilities, authorities, and others mark their underground facilities before work begins. Excavators can call the one-call system in their state or the national one-call number: 811. Dominion Energy typically receives and responds to more than 50,000 excavation activity notifications per year near our underground transmission pipelines. These one-call programs are a valuable component to protect our system and to ensure safe operations. It’s important to us that our customers and employees know how to take safety precautions around both electric and gas infrastructure. And when there is an emergency gas-related call, company employees are on-site 98 percent of the time.
In Ohio, Dominion Energy teamed up with the Cleveland Indians to promote the Call 811 safety message in 2017 through signage at Progressive Field. The venture built on similar promotions with the NBA’s Cleveland Cavaliers, the American Hockey League’s Cleveland Monsters and the Arena Football League’s Cleveland Gladiators at the Quicken Loans Arena.
In Utah, employees make roughly 100 safety presentations each year to community organizations, informing customers about earthquake preparedness, natural gas safety, the safety of high-pressure pipelines near their homes and businesses, ways to identify leaks, and what to do in the event of an incident.
We conduct campaigns every fall to encourage customers to have a licensed heating expert check furnaces before winter, and we partner with Utah Poison Control, the Utah Health Department, and the Utah Unified Fire Authority each year to educate the public about carbon monoxide. We sponsored the Utah Safety Council Safety Conference and Expo in 2017 and 2018, and plan to continue our sponsorship in 2019.
Dominion Energy operates over 2,300 storage wells, which are used for injection and withdrawal of gas from our underground natural gas storage formations. We have completed well casing inspections using advanced technology logging tools on over 80 percent of these storage wells, and have plans to expand the program each year.
Dominion Energy’s storage holdings also include 21 underground depleted hydrocarbon reservoirs in Ohio, West Virginia, Pennsylvania, New York and Utah, and three aquifer reservoirs in northern Utah and Wyoming. Aquifers are underground, porous and permeable rock formations that act as natural water reservoirs that, in some cases, may be used for natural gas storage.
Dominion Energy has successfully managed its natural gas storage facilities since it began storing natural gas for customers in the 1930s. Many of our storage wells are depleted production wells that have been redesigned for gas storage; other storage wells have been drilled specifically for that purpose.
The storage wells are designed to withstand the high pressures associated with compression and withdrawal. Ongoing casing integrity inspection logging allows for monitoring the condition of the casing that contains the storage pressure in the wells. Our wells contain up to three concentric linings. On many, the innermost casing is cemented to the surface to provide additional leak prevention.
Dominion Energy has been using electronic logging since 2000, before it was required by the Pipeline and Hazardous Materials Safety Administration. The process involves lowering a high-resolution electronic device into the well to take electromagnetic readings over the entire length of the well.
Under normal operations, fugitive methane emissions from underground storage field wellheads owned by Dominion Energy constitutes less than 1 percent (and usually closer to 0.2 percent) of Dominion Energy’s total inventoried methane emissions. This estimate is based on the methodology specified by the EPA’s Greenhouse Gas Reporting Program for underground storage facilities.
We take into account a variety of parameters in deciding how often to perform casing inspection logging on our storage wells. This work is prioritized using a risk ranking, which takes into account factors such as depth, operating pressure, and location. In the event of a major leak, Dominion Energy has in place site-specific Emergency Plans for each storage field.
Our integrity programs include:
- Periodic well casing integrity inspections for internal and external corrosion;
- Regular inspections to verify well status and pressure, and to look for signs of atmospheric corrosion, vent gas, or leaks;
- Remote monitoring; and
- Monitoring of third-party drilling activities in and around storage pools.