What is the average life expectancy of buried, twisted pair (copper) telephone cable?

Question

From the main building, I am dealing with underground telephone cable (cable is meant for and armored for underground use and contains 100 pair of wires) and runs about 350 feet to another building; this cable runs underneath a two-lane highway. The cable was installed perhaps better than 40 years ago. Lately, when there is a heavy rainfall, some of the telephone circuits on these line gets a bit of static or cuts our all together (the telephones used on these lines are Nortel digital telephones with a Meridian controller and line cards).

With the number of problems I have been experiencing, should I suspect I am having wire pair going bad and should probably replace the cable. Would it be worth while to replace the cable with fiber-optic, especially since I am driving some computer network traffic over some of these cable pair via ADSL modem repeaters. My other option would be to replace the cable with a new copper twisted pair cable.

Answer 1

go fiber-optic!!

Answer 2

I would recommend replacing the whole run, wires, conduit and all!  Get a direction boring machine and go for it! Fiber is the way to go if you can afford it, or have gotten your techs the training and tools!