30 June 2001
(5) Compaction. Compaction requirements for the subgrade and granular layers are
expressed as a percent of maximum CE 55 density as determined by using CRD-C653, Standard Test
Method for Determination of Moisture-Density Relations of Soils. For granular layers, compact the
material to 1 00 percent of maximum CE 55 density. Select materials and sub-qrades in fills must have
densities equal to or greater than the values shown in Table 3-7, except that fills will be placed at no less
than 95 percent compaction for cohesionless soils (PI - 5; LL 25) or 90 percent compaction for cohesive
soils (PI > 5; LL > 25). Subgrades in cuts must have densities equal to or greater than the values shown
in Table 3-7. Subgrades occurring in cut sections will be either compacted from the surface to meet the
densities shown in Table 3-7 removed and replaced before applying the requirements for fills, or covered
with sufficient material so that the uncompacted subgrade will be at a depth where the in-place densities
are satisfactory. Depths in Table 3-7 are measured from the surface of the aggregate, and not the
surface of the subgrade.
Compaction Requirements for Helicopter Pads and Slide Areas
Depth Below Pavement
c. Drainage. Drainage is a critical factor in aggregate surface airfield design, construction, and
maintenance. It should be considered prior to construction; and, when necessary, serve as a basis for
(1) Provide adequate surface drainage to minimize moisture damage. Quick removal of
surface water reduces absorption and ensures more consistent strength and reduced maintenance.
Drainage must not result in damage to the aggregate surfaced airfield through erosion of fines or erosion
of the entire surface layer. Ensure changes to the drainage regime can be accommodated by the
surrounding topography without damage to the environment, or the newly constructed slide area or pad.
(2) The surface geometry of an airfield should be designed so that drainage is provided at all
points. Depending upon the surrounding terrain, surface drainage can be achieved by a continual cross
slope, or by a series of two or more interconnecting cross slopes.
(3) Provide adequate drainage outside the airfield area to accommodate maximum flow. Use
culverts sparingly, and only in areas where adequate cover of granular fill is provided over the culvert.
Evaluate drainage for adjacent areas to determine if rerouting is needed to prevent water from other
areas flowing across the airfield.
d. Maintenance. The two primary causes of deterioration of aggregate surfaced areas requiring
frequent maintenance are the environment and traffic. Rain or water flow will wash fines from the
aggregate surface; traffic action causes erosion of surface materials. Maintenance should be performed
at least every six months, and more frequently if required. Frequency of maintenance will be high for the
first few years of use, but will decrease over time to a constant value. Most of the maintenance will
consist of grading to remove ruts and potholes and replacing fines. Occasionally, the surface layer may