Vectren Energy Delivery has begun this year’s effort to replace gas mains and service lines throughout the state. The company says it will invest nearly $51 million this year to retire 80 miles of pipeline infrastructure in 26 cities. The effort is part of a multi-year program to replace about 1,200 miles of bare steel and cast-iron pipeline infrastructure in nearly 75 Indiana cities and towns, which began in 2008. Vectren says, in most cases, a plastic system is being installed to replace the current bare steel and cast-iron system.