Preparation of the ground pad involves stabilizing the existing base by adding strength and decreasing permeability. Contractors with experience building roads are likely best equipped to perform this task. Pad preparation includes creating a crown at the center point of the pile and providing a gradual slope away from the center. Good drainage is provided with slopes of 1 to 2 percent. Reduced water permeability of the pad can be best accomplished by mixing lime, fly ash, or cement in the soil prior to compaction.
Check fly ash prior to use to ensure the absence of heavy metals.
The amount of compression necessary for a good pad should approach 95 percent of the standard proctor density. This value can be measured on site by the engineering firm using a density gage. The area surrounding the pad should be well drained to remove water running off the pile and pad. Most pads vary in surface area between 1 to 2 acres. One inch of precipitation on a 1 acre surface results in 27,152 gallons of water.