Alexandria Central Zone Conveyance System

• Contract:EAC was awarded a 110million LE contract in consortium with MC int. for the construction of 3.5 Km long tunnel to be used as a main collector for sanitary drainage in Alexandria.
• Owner:Alexandria General Organization for Sanitary Drainage (AGOSD)
• Engineer:Dr. Ahmed Abdel Warith
• Location:
  • Collector: Flowing from the Cornish of Alexandria Eastern Harbor to the existing Furn El Gueraya Collector, then to Qabbari Collector to the West Treatment Plant.
  • The Connections: Will transfer wastewater from existing gravity sewer network to the new collector.
• Excavation Depths:Ranging from 8 to 18 meters below ground level.

The project entailed the construction of 13 jacking and/or receiving shafts in the 3500m tunnel path. The shafts' construction involves caisson sinking and diaphragm walls. Diaphragm wall shafts are either circular or rectangular according to site condition. Since dewatering is not allowed two techniques are used depending on soil formation at each shaft location.

The first is to pour a concrete base plug under water then water is removed from the shaft and construction continues. The second technique is soil replacement in which jets of air and water are used at the required depths to turn the soil into a slurry, with low pressure pumps cement is injected displacing the slurry soil upwards and replacing it, then after the cement hardens excavation starts in dry condition.