3.4.4 Water Intrusion through Overflow
During the construction of the airfield pavement, there was evidence that the water levels in several areas were relatively high during 2005 and 2006 as indicated in Photos 26 to 29. The photographs indicated the water level in the canals were as high as +0.0 m MSL. Figure 35 shows the scenario where overflow from the secondary canal could result in flooding of the subgrade sand beneath the pavement. It should be noted that if there is no subsurface drainage, then it does not matter when the water had entered the subgrade sand, the water would remain in the sand for a while.