Pipeline transportation is one of the safest and most cost-effective ways to transport natural gas and hazardous liquid products. As the United States continues to develop and place more demands on energy transportation, it becomes necessary to invest in upgrading its infrastructure, including aging pipelines. In 2011, following major natural gas pipeline incidents, DOT and PHMSA issued a Call to Action to accelerate the repair, rehabilitation, and replacement of the highest-risk pipeline infrastructure. Among other factors, pipeline age and material are significant risk indicators. Pipelines constructed of cast and wrought iron, as well as bare steel, are among those pipelines that pose the highest-risk. To illustrate the progress pipeline operators are making in the replacement of aging gas pipelines, PHMSA provides an annually-updated online inventory of high-risk pipeline infrastructure by state. Specifically, the dynamic inventory highlights efforts to replace iron and bare steel gas distribution pipelines and shows trends in pipeline miles by decade of installation.
Cast and Wrought Iron Pipelines
Cast and wrought iron pipelines are among the oldest energy pipelines constructed in the United States. Many of these pipelines were installed over 60 years ago and still deliver natural gas to homes and businesses today. However, the degrading nature of iron alloys, the age of the pipelines, and pipe joints design have greatly increased the risk involved with continued use of such pipelines. The Pipeline Safety, Regulatory Certainty, and Job Creation Act of 2011 calls for DOT to conduct a state-by-state survey on the progress of cast iron pipeline replacement. For updates on the states’ progress, contact information and incident and mileage data, the public should visit PHMSA’s state pipeline profiles.
The amount of cast and wrought iron pipeline in use has declined significantly in recent years, thanks to increased state and federal safety initiatives and pipeline operators’ replacement efforts. Twenty two states and one territory have completely eliminated cast or wrought iron natural gas distribution lines within their borders, Alaska, Arizona, Arkansas, Colorado, Hawaii, Iowa, Idaho, Minnesota, Montana, Nevada, New Mexico, North Carolina, North Dakota, Oklahoma, Oregon, Puerto Rico, South Carolina, South Dakota, Utah, Vermont, Washington, Wisconsin, and Wyoming.
Approximately 97 percent of natural gas distribution pipelines in the U.S. were made of plastic or steel at the end of 2018. The remaining 3 percent is mostly iron pipe.
Bare Steel Pipelines
Uncoated steel pipelines are known as bare steel pipelines and while many of these pipelines have been taken out of service, some of these pipelines are still operating today. The age and lack of protective coating typically makes bare steel pipelines of higher risk as compared to some other pipelines and candidates for accelerated replacement programs.
From the early 1900’s through today, the integrity of energy pipelines has benefited from improvements in pipe manufacturing, pipe materials, construction methods, and maintenance practices.