Ask Mr. Smarty Plants

An oak tree root system is extensive but shallow. The ground area at the outside edge of the canopy, referred to as the dripline, is especially important. The tree obtains most of its surface water here, and conducts an important exchange of air and other gases. Any change in the level of soil around an oak tree can have a negative impact. The most critical area lies within 6 to 10 feet of the trunk. No soil should be added or scraped away from that area. Construction activity is a great threat to trees. Do not allow any parking within the dripline or piling of materials, waste, etc. in that area.

Paving should be kept out of the dripline and no closer than 15 feet from the tree trunk. If at all possible, use a porous paving material such as brick with sand joints, open bricks, bark, gravel, etc., which will allow some water penetration and gas exchange. Even with porous paving, the area around the trunk-at least a 10 foot radius-should be natural and uncovered.

We realize these are difficult restrictions, and your construction crews will not be happy. However,  you will need to make a choice between the trees and the construction. If you fail to make provisions for the needs of the trees, even if the trees appear to have survived, they probably have only a few years before they succumb to disease or starvation.