Khayam Main Drain to replace polluted network of traditional drains. Total length of tunnel 21.5 km at depth of 20-40 m into which a variety of smaller sewers will discharge. 400 km system of watercourses, surface drains and tunnels planned, of which 260 km complete and 63 km under construction. Three contracts using methods matched to ground conditions: 4,042 m of 2.8 m diameter horseshoe configuration; 5,625 m of 3.7 m TBM drive using 4.3 m Lovat ME170SE EPB; and 1,830 m of 4.6 m diameter cut-and-cover and NATM. Another 10 km of 1.8 m diameter horseshoe configuration is being driven for outlets. Supervision and technical support: Gueno and Maunsell; contractors: Debleh-Alamoot for Contract 1 ($1.4m), Andrade Gutierrez jv for Contracts 2 ($12.4m)and 3 ($8.85m); designer: Omran Mohit Zist. March 1999.
