In areas where the taxiways cross the secondary canals, concrete box culverts (Photo 7) were constructed with the bottom elevations of the concrete structures at -1.45 to -1.55 m MSL as shown in Figure 13. A 10 cm of C1 sand (with fines content of less than 10%) was placed below the box culverts as a working platform or leveling mat. It should be noted that the bottom elevations of the box culverts are, in general, lower than the depths of the sand blanket, therefore discontinuity in the sand blanket across the box culverts is expected as illustrated in Figures 14 and 15. Photos 8 and 9 taken along various locations have shown different conditions of the subsoil encountered in the secondary canals.