Question
Our village was putting in sewer pipes, and inavertanley hit my tree with thier digger truck exposing the tree trunk three quarters the way down. Also left roots exposed on one side from March to present 2008. Will the tree die?

Answer
The damage will depend on the species of tree. Conifers can seal over wounds faster than hardwoods thereby not allowing fungi to enter but sometimes the sap from conifers will attract insects that bore into the trunk. The wound should be cleaned-cut any loose bark from around the wound this will allow the tree to heal over the wound faster. I would spray the wound with an insecticide called Merit-this will protect it from insect attack.
The over all damage from the wound will depend on the extent of the area around the trunk. Tree quarters around the trunk can cause some die back in the branches. The trees water transportation system is damaged thereby the foliage can not get the needed water. I have seen trees with almost all the bark off survive--this depend on the weather condition and rain fall. watering the tree with 1 inch of water per week will help (place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop).

Root damage will depend on the percent of the total root system damaged. If more then 30 % of the roots are damaged then die back will occur. Exposed roots should be cut off clean and covered if possible.

I would in writing let the city know of the damage and if the tree dies expect them to replace it. I would expect the tree to make it but with some of its crown dying back. Even in that case you might want to seek some sort of compensation fro the damage.