DOUBLE WALLED CORRUGATED (DWC) HDPE PIPES: Supply and erection of double walled corrugated (DWC) HDPE pipe to be laid 1mtr. below ground level including excavation (making necessary trench), placing the pipe in position and back filling with excavated soil etc. of the required size. Double walled corrugated (DWC) HDPE pipe 160/ 136mm (outer/ inner dia.)