Tunnel construction on the US$302M San Francisco Hydroelectric Power Project (SFHPP) in Ecuador is scheduled to start in December this year. The scheme involves the excavation of an 11.2km long headrace tunnel that will utilise both drill and blast and TBM techniques.
Consortium Hidropastaza, a JV of Hidroagoyan, Odebrecht and Ansaldo/Coemsa, will begin work shortly on access roads to Adit 4, positioned at PK 10+395 along the 11.2km long tunnel.
In December this year the JV will excavate using drill and blast from Adit 4 at 7.5m diameter, 413m towards the planned TBM drive and 847m towards the penstock at the SFHPP.
On completion precast sections will be installed beginning at Adit 4 and ending at PK 9+982. This will allow the TBM, a Robbins 194-272-I, to be assembled and advance to the excavation face, complete with back-up, ready to commence boring on the remaining 9.8km long, 7m diameter headrace drive. The drive is scheduled to begin in April 2003.
The TBM is equipped with precast concrete installation jacks to line the tunnel over a total length of 200m during the Blanco, Verde and Machay River crossings. The tunnel is being constructed through variable, but generally good, rock comprised mainly of granitic gneiss, sericitic schists and granite, thus allowing the limited lining. The tunnel slopes varying from 0.13% to 0.56% permitting adequate drainage during construction.
On reaching PK 0+130, the TBM will be disassembled and transported back down the tunnel to Adit 4 for shipment. Complete construction of the run of the river underground power scheme is scheduled to take four years.
The project was awarded to the JV by the Grant Authority CONELEC (Electricity National Council) as a BOT scheme over 30 years, including construction.
Located downstream of the existing Agoyan Hydroelectric Power Plant the 230MW SFHPP will generate 1420 GWh/year, boosting the area’s power supply.
Related Files
Diagram of the underground construction
Map showing location and alignment of the 11.2km long headrace tunnel
