Mexico City plans for stormwater

摘要

Workers repair and maintain the deep drainage sewers in Mexico City in advance of the wet season. The tunnel system is to take up to 180m~3/s of combined stormwater and sewage.rnBut long-term settlement in the entire valley where the capital is located has been reducing capacity and a new tunnel system - the Eastern Discharge Tunnel (Tunel Emisor Oriente) - is under construction.rnThe National Water Commission (Conagua) is developing the drainage upgrade scheme to both increase capacity and reduce flood risk by 2012. In total, the new 7m i.d. sewer will be 62km long with 24 shafts of 30m-150m depth, the majority being 12m diameter but some 16m wide.rnGeology comprises sandy clay, gravel, tuff and pumice, and there are large boulders.rnSix EPBMs are being used tornbore the tunnels - three from Herrenknecht (2 × 8.7m dia., 1 × 8.89m dia.) and three from Robbins (3 × 8.93m dia.).rnThe contractor is the Constructora Mexicana consortium, which includes !ngenieros Civiles Asociados,rnCarso Infraestructura y Construccion (CICSA), Construcciones y Trituraciones (COTRISA), Constructora Estrella (CESA) and Lombardo Construcciones.rnThe contract value is US$705M.