In summary, the drain channels in the apron area carry the surface water from the apron to the drain canals. These channels were constructed higher than the bottom of the sand blanket; therefore they did not block the passage of water in the sand blanket. Beyond the drain canals were a series of secondary canals in contact with original clayey soils and sand blanket material depending on the locations. In areas surrounded by clayey soils, there was no connection between the secondary canal and the adjacent sand blanket beneath the pavement, hence no possible subsurface drainage. In areas where the secondary canals were in direct contact with sand blanket, some subsurface water flow into the secondary canals through the weep holes and joints of concrete panels would be possible, but the weep holes might not be designed to carry subsurface water from the sand blanket effectively.