Eleven. Old gas lines in Danville, some dating back to the 1920's, are getting replaced. The current gas pipes, some 90 years old, are made from cast iron. Soon work will begin in the North Main Street area as crews replace about four miles of gas and water lines. It's a small section of the 356 mile gas pipelines that run throughout the city that have to be replaced. That project started 14 years ago. Allen Wiles/Danville Utilities: "We monito the leaks and on our gas main and we repair those leaks but when the piping or the main has reached the end of their useful life it's better to just replace them with a different product." There are more than 44 miles of pipe left to replace. So far their work has cut down on the number of crack and leak repairs. Danville receives its natural gas from the Transcontinental Gas Pipeline.