Panama prepares for EPBM deliveries
Panama prepares for EPBM deliveries Oct 2010
SELI News Release
Two EPBMs are in final shop testing before dispatch by SELI to the Pando and Monte Lirio hydroelectric projects in Panama. The first machine was accepted by the client, Electron Investment SA, at the SELI factory in Aprilia, Italy this week and will be dismantled and shipped to Panama where it is expected to start boring the longer 7.9km headrace tunnel for the Monte Lirio hydro scheme in January 2011.

Factory acceptance at Aprilia

The second, almost twin TBM for the 5.2km Pando scheme headrace will be delivered in November for an expected start in February 2011.
Electron Investment SA awarded SELI a $100 million EPC (engineering, procurement, construction) contract for the two tunnels. Under the terms of the contract SELI is in charge of the entire tunnel construction cycle, from design to final work handover.
The developer, Electron Investment SA, is a joint venture between Inveravante Inversiones Universales SL of Spain (51%), and the Panamanian entity Grupo Eleta (49%). Total cost of both installations is estimated at $291.7 million.
SELI will operate in the country through a subsidiary, SELI Panama SA, which was founded in November 2009 to carry out operations and supervise advance works.
The tunnels lie almost entirely in lahar, a particular volcanic mudflow, which exhibits highly variable characteristics, behaving locally as completely loose ground. Lahar formations are originally a mixture of water, ice, and volcanic sediments generated when hot gases and magma are ejected under and on to snow and ice fields, which rapidly melt and flow down the slopes of the volcano.

The technical specifications of the TBMs

Pando Tunnel Monte Lirio Tunnel
Excavation diameter 3.72m 3.92m
Disc cutters 17in 17in
Max cutterhead thrust 13,560kN 13,560kN
Cutterhead speed 0-4 rev/min 0-4 rev/min
Cutterhead drive power 600kW (4 x 150kW motors) 600kW (4 x 150kW)
Due to the complex and variable geological conditions, SELI decided to design and use two mixed-face EPBMs designed to operate in both closed and open mode and to change between the two without modifying the machine arrangement. The machines are expected to operate in open mode in the presence of rock mass, including dense lahar and ancient lava flows, and to change to closed mode for passage through unstable and loose soils.
Concurrent with excavation, the machines will install a precast concrete segmental lining that comprises five segments and a key in each 1.2m long ring. The 25cm thick lining will provide an external and internal diameter of 3.5m and 3m for the Pando headrace and 3.7m and 3.2m for the longer Monte Lirio waterway.
The projects are located on the Chiriquí Viejo River in Western Panama. Both are run-of-the-river installations that will operate in cascade, the tailrace of the Pando powerhouse connecting directly to the headrace of the Monte Lirio plant (Fig 1).
With a total 85MW installed capacity, of 33MW at Pando and 52MW at Monte Lirio, a firm capacity of 57.5MW will generate approximately 430 GWh of energy per year.

Fig 1. Plan of the two TBM headrace drives

Located about 4km west of the Volcán town in the Bugaba District in Chiriquí Province, the Pando hydro plant includes:
• a 32m high water-edge-type dam;
• a 900,000m3 reservoir;
• a 63m-high surge shaft on the 5.2km-long headrace; and
• a powerhouse.
The Monte Lirio plant is located about 1km from the Plaza Caisán in the Renacimiento District includes:
• a 15m high dam at the same location as the Pando powerhouse;
• a reservoir;
• the 7.9km-long headrace plus a 74m-deep surge shaft; and
• a powerhouse.
Works are scheduled to be completed and the schemes commissioned during 2012.
Panama awards hydro scheme TBM drives - TunnelTalk, March 2010

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