The Pennsylvania Public Utility Commission on Thursday approved Peco Energy Co.'s long-term infrastructure-improvement plan, setting the stage for the company to accelerate a pipe-replacement program for its natural-gas utility.

Under Peco's plan, the company will increase its projected annual spending to replace aging natural-gas service lines from $14 million to $34 million per year.

Peco's system includes about 1,731 miles of iron mains and bare-steel mains and customer-service lines. Those mains, some built in the 1800s, comprise only 14 percent of Peco's system but account for 86 percent of leaks, according to the PUC.

Under the plan, Peco pledged to replace its oldest high-risk cast-iron and all of its bare-steel services in about 10 years and replace all of the cast-iron and bare-steel mains in its system in about 34 years.

Contact Andrew Maykuth at 215-854-2947, @Maykuth on Twitter or amaykuth@phillynews.com