T BM excavation of two tunnels for the Trasvases Manabi water supply and irrigation project in the Manabi Province on the Pacific Coast of Ecuador, South America, is more than 8.3km through the first and longest of the tunnels at 11.4km.
Main contractor Odebrecht of Brazil started excavation of the segmentaly lined tunnel in February 2000 and expect to hole-through in December to complete more than 11km of 4.04m excavated diameter tunnel (3.5m lined diameter tunnel) in less than 10 months.
Average progress, at 1,020m/month, has surpassed the contract’s projected rate of advance, and excavation is now some two months ahead of programme. To date the best rate of advance in a 24h day (working three eight hour shifts) is 67.4m, recorded in July 2000. The best seven-day week recorded in week 26 is 400m and the best month recorded in September 2000 was 1,505m.
The tunnel is being excavated using a Robbins double-shielded TBM and is lined with the hexagonal design of precast concrete segmental lining.
The TBM and all its backup equipment are supplied under a rental agreement by Seli of Italy.
Once the TBM completes the first 11.4km long tunnel in December 2000, it will be transported some 100km to the portal of the second 4km long tunnel. Excavation of Tunnel Two is programmed to start in February 2001 and to be completed by June 2001.
The two tunnels, linking two existing reservoirs, are the critical path elements of a contract awarded to Odebrecht by the Centro de Rehabilitacion de Manabi, the project owner, started in May 1999. In addition, the $140M contract includes the civil and mechanical works for a 16m3/second pumping station to lift water from the La Esperanza reservoir into a 6km long section of pipeline that feeds into the 11.4km long tunnel and discharges into the Poza Honda reservoir. The second 4.1km long tunnel transfers 4m3/s of water from the Poza Honda reservoir to the Mancha Grande River, both to increase water supply to Portoviejo, the principal city of the province and its surrounding region.
