On June 28, 1993, natural gas leaked from a 12-inch high-pressure cast iron natural gas line at Pennsylvania Avenue and 30th Street, SE. Fire, followed by an explosion, apparently caused by a spark from a stalled van's starter motor, resulted in one fatality and several injuries. As a result of the incident, the Commission directed Washington Gas Light (WGL) officials and Commission staff to develop a Cast Iron Replacement Program ("CIRP") to rapidly retire 8-inch and 12-inch high-pressure cast iron pipes, which are more susceptible to failures. Although WGL already had a pipe replacement program, the CIRP was implemented as an addition to WGL's existing pipe replacement program.

WGL submitted a ten-year plan for the CIRP in November 1994. The plan called for the replacement of the 8-inch and 12-inch cast iron pipes. The CIRP was launched in 1994 and was successfully completed in 2004.

By the end of October 2004, when the CIRP jointly developed by the Commission and WGL was completed, a cumulative total of 15.8 miles of cast iron mains had been replaced.

In its continued efforts to enhance the reliability and safety of its natural gas distribution system, WGL is implementing an on-going program of replacing small diameter (less than 8 inches in diameter) cast iron pipes with plastic pipes. Since 1984, WGL has replaced 178 miles of small diameter cast iron pipes.