Risk-Management Process For Urban Utilities

The distribution of natural gas in an urban utility has inherent risks. Distribution networks are located underground, out of sight and typically under pavement in close proximity to buildings, residences and subsurface structures.

Urban customers in older cities are located in densely populated centers that have piping systems dating back to the 1800s. These facilities vary widely in composition, pressure, age and type. Many factors influence the risk of distributing natural gas in such an environment. Despite the many risks, the natural gas distribution industry has an extremely safe and reliable record of transporting gas to millions of consumers every day.

The industry’s safety record is really a product of the due diligence demonstrated by the utilities that transport the commodity. Since the Pipeline and Hazardous Materials Safety Administration (PHMSA) enacted compliance regulations decades ago (CFR 49 Part 192), utilities have had processes in place to assess the health and safety of their systems. While many of these processes have been in place for many years, utilities are always looking to improve their procedures, and in many cases, go above and beyond the federal and state requirements to create a safe and reliable environment.

Philadelphia Gas Works (PGW) exemplifies one of these utilities that constantly looks for better ways to operate and maintain its systems. PGW began distributing gas in 1836 in the oldest parts of Philadelphia, PA. Through the years, the system has grown to encompass 6,000 miles of gas mains and services under some of the busiest, oldest and most complex streets in the nation. The system is comprised of a laundry list of pipe materials and fittings, with the highest percentage, or more than 1,600 miles, cast iron. Much of this pipe dates back to the late 1800s.

The characteristics of PGW’s distribution system create a daily challenge to the operators to maintain a safe, reliable service to the community. This is a challenge that PGW takes seriously and keeps managers constantly searching for new and innovative ways to improve. This dedication of evolving and improving is evident upon evaluation of PGW’s risk-management process. Risk management, by that name, formally began in the 1980s at PGW and has evolved through the decades into a sophisticated system today.

Historical Perspective

In the 1980s, as its distribution system began to show signs of aging, PGW implemented a formal risk-based process to replace, rehabilitate or remove facilities that posed the highest risk to public safety and its ability to reliably serve its customers. PGW then and now operates predominantly an inches water column pressure gas distribution system.

The system’s operators recognized that the highest risk for an incident was the break of a small-diameter cast iron main whose escaping gas could migrate into a building basement. This type of failure of a cast iron main introduces a significant amount of gas to the environment when compared to a steel corrosion leak and presents a higher safety risk to the public. As a result, PGW began to evaluate its cast iron mains on several factors, including incidents on the city block in which the main is located, age of the main, number of failures of the main, failures of the main’s supporting media, mains within the slope of a parallel excavation, and mains within a crossing excavation.