Question
We are digging near an oak tree because we are putting in a new front entrance.  This oak tree is approximately 10 feet from the house and has a diameter of 2 1/2 feet.  The digging of the new entrance will encroach to within three feet of the tree, leaving 200 degrees of the root structure untouched.  We would like to know if there are things we can do to lessen the stress on the tree before/after and if we will have to do any sort of support afterward to prevent in from falling down in a windstorm.

Answer
Damaging more than 1/3 of the rood will cause some die back to the foliage. What is happening the roots system left can not support (with water and food) the foliage that the original root system was supporting therefore some of the foliage will die. There should not be any problem with the support as far as wind throw. The remaining roots will hold the tree just fine.
Keep the traffic around the tree down to a bare minimum (no traffic). Do not pile anything on the roots under the tree and do not add any soil to the area under the tree. I would rope off the area so no one will go into the area during construction.  After the cinstruction has finished I would fertilize the tree with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. I would water once a week with 1 inch of water-place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop.