A perimeter canal was built adjacent to the polder within the airport site with the bottom elevations of -1.9 m MSL as shown in Figure 12. Two (2) pumping stations were located to the southeast and southwest corners of the polder system with maximum pumping capacity of 12 m3 per second. Primary canals without concrete lining (or side concrete slab) were excavated in non-airfield pavement areas for connecting the water passage from the pavement areas to the perimeter canal. Another series of canal, referred as secondary canals, was constructed next to the airfield pavements to control the drainage condition of the airfield pavement. These canals were built with concrete linings and weep holes at 5 m spacing on the side slopes and the bottom slab. The bottom elevation of the secondary canal was designed at -1.15 m MSL. It should be noted that the top edges of the secondary canals were designed at an elevation of +0.0 m MSL. Apart from the primary and secondary canals, small canals, such as drain channels were constructed around the apron areas, which were used for draining the water out from the apron areas.