. >> reporter: ad perfop operates than 40,000 miles of transmission line. they carry electricity from power plants to substations where it is then delivered to your home. the lines are big and building them is difficult, dangerous and expensive. the problem is half the nation's transmission lines are more than 40 years old and some were built more than a hundred years ago. adp is replacing the lines in the northeast and midwest. you basically want to make sure the system is as efficient as possible. sometimes a new line and sometimes rebuilding an existing line. it's not a one size fits all approach. >> reporter: magnifying the need for grade upgrade is the new emission standard set by the epa. coal-fired plants are being shut. that powers millions of homes. that generation needs to be replaced with new plants which also means new transmission lines. but the new system doesn't look like they did a hundred years ago. they are meant to have higher capacity so they can work for another 60 to 80 years. in ft. wayne, indiana, the company is upgrading its storm s