The level of work to replace cast iron and bare steel pipe has decreased in volume since 2009, when it was introduced. However, the Gas Distribution Integrity Management Program (DIMP) still requires a significant amount of construction work. The U.S. Department of Transportation (DOT) estimated that at the end of 2021, 38,403 miles (61,804 km) of bare steel and 18,031 miles (29,018 km) of cast iron pipelines were still in service in the United States Most of this pipe is in eastern cities with older infrastructure systems, such as New York, Boston, Washington, D.C. and Philadelphia.
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