EPBM push in Panama Feb 2011
Patrick Reynolds, Freelance Reporter
The first of three EPBMs to be supplied and used by Seli to construct connected headrace tunnels for hydropower projects in Panama is about to be launched on the narrow valley drives through variable lahar volcanic rock which is an uncommon geological formation in tunnelling. The first two machines of 3.92m and 3.72m diameter are to be used on the headrace tunnels for the private-enterpise Pando-Monte Lirio scheme while the third, a 6.79m diameter EPBM, will be used on the El Alto project. All three projects are high in the steep Chiriqui Viejo River valley, close to the border with Costa Rica.
Panama's first EPBM at Seli's plant in Italy

Panama's first EPBM at Seli's plant in Italy

The first of the TBM trio, the 3.92m diameter machine, will begin this month (Feb 2011) to excavate the Monte Lirio headrace section and its 3.72m diameter near-sister machine is due to follow in April. In recent weeks work has focused on site assembly for the Monte Lirio shield following shipment from Italy and its inauguration last October at Seli's Aprilia plant.
A few months after being awarded the US$105 million engineering, procurement and construction (EPC) contract for the equipment and tunnelling works, Seli established a local company, Seli Panama SA, in November 2009.
The Monte Lirio and Pando headraces are 7,878m and 5,161m long respectively and both are to be advanced below the groundwater table through lahar rock that comprises solidified volcanic slurries of variable properties. Site studies have classified the lahar into two types, depending on fines context: matrix-supported and clast-supported. Cohesion is not part of the rock's classification.
To advance through the variable geology, the EPBM cutterheads are dressed with 17in discs as well as rippers. Maximum thrust of the machines is 13,560kN and both can operate in either open or closed mode with muck haulage in trains of muck skips.
  • Assembly of the Monte Lirio TBM underway in Panama

    Assembly on site of the Monte Lirio TBM......

  • The Monte Lirio drive is due to complete in mid-2012

    .......ready for launch this month

The Monte Lirio and Pando tunnels will be segmentally lined to 3.2m and 3m i.d. respectively, with 250mm thick x 1.2m long rings of five segments and a key. The segments are being cast by Costa Rica-based Euroconcretos SA using moulds supplied by Seli.
The hydro scheme is a cascade system being developed in the steep-sided, upper Chiriqui Viejo Valley, close to the border with Costa Rica. The developer, Electron Investment, is a 'special vehicle company' with a 50-year concession to exploit the hydro resources in the upper part of the valley at the Monte Lirio and Pando dams. Estimated cost of the scheme is about US$292 million.
Assembly of the second EPBM for launch in April

Assembly of the second EPBM for launch in April

Late last year it was anticipated that the Monte Lirio TBM would be launched by January with the second Pando shield getting underway this month. Despite the slight delay in schedule, the machines are expected to keep pace with the original programme for completion in July and December 2012 respectively. The anticipated commissioning times of the power plants are expected to be about the same as previously planned.
Funding for the hydro scheme is being provided by debt and equity with loans from lenders including the International Finance Corp and the Inter-American Development Bank, and the equity provided by Electron Investment via its joint owners, two investment vehicles owned by entrepreneurs, one local and the other Spanish.
Separately, Seli's supply of the 6.79m diameter EPBM is for the El Alto project, which is the next stage in hydro development in the Chiriqui Viejo Valley and is downstream of Pando-Monte Lirio. The contract was awarded late last year, just as the Monte Lirio TBM was being inaugurated at the plant and readied for despatch to Panama.
Panama awards hydro scheme TBM drives - TunnelTalk, March 2010
Panama prepares for EPBM deliveries- TunnelTalk, October 2010

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