National Trail Surfaces Study

Installation of Aggregate Surfaces at Bradford Woods

The installation of the aggregate surfaces at Bradford Woods conformed to the following protocol:

Prior to installing the crushed rock (aggregate) surfacing material, the trail bed shall be shaped to reflect the same linear grade and cross slope as the desired finished surface. The trail bed shall be uniformly smooth and compacted to a rate of 90 percent.

The rock shall be from a quarry and have angular fractured surfaces. It shall be ¾ inch minus 100 percent crushed and shall be free of vegetable matter and other potentially harmful substances. It shall be of such nature that it can be compacted readily under watering to form a firm and stable surface. The crushed rock shall be inspected by a representative of the contracting agency prior to delivery to the worksite to insure material quality. The crushed quarried rock shall conform to the grading requirements shown in Table 6.

The crushed rock shall be applied to the trail bed at a minimum depth of 6 inches. The application shall be performed in two separate 3-inch lifts. Each lift shall be shaped to the proper linear grade and cross slope prior to compaction. Compaction shall be performed by using either a viberplate compactor or a vibratory roller and shall achieve a minimum compaction rate of 90 percent. The crushed rock shall be kept moist to achieve the maximum rate of compaction. Native soil shall be blended into the last 3-inch lift of crushed rock to soften the color and texture of the finished trail tread. The rate of application shall vary depending on the clay content of the native soil. The finished surface of the trail tread shall be uniformly smooth without holes or concave depressions that can trap water. Photos that illustrate the installation of each trail section are included in Appendix D.