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Panama awards urgent Esti headrace repair Dec 2011
Execution of major repairs and lining works to the 4.7km long x 9m diameter pressure tunnel of the Esti hydro scheme in Panama is awarded to a joint venture of SELI and OSSA (Obras Subterraneas SA) with designer Lombardi Engineering of Switzerland.

Poor geology harassed original excavation progress

Owned by AES Panama, a division of parent company AES Corporation of the USA, the US$53 million contract is awarded to repair the headrace tunnel which has collapsed in several places causing a long standstill of the plant's operations.
AES declined to provide a statement when contacted, but a visit by TunnelTalk to the original construction contract highlighted difficult geological conditions and the need to realign the headrace to prevent hydrofracturing under shallow cover.
The power plant was built in the early 2000s and is vital for Panama's energy requirements. The repair contract was signed in June 2011 and is set for a tight target date completion of 1 May 2012.
Works by the Italian-Spanish JV, led by SELI, is programmed over two phases. During the the first phase, collapsed materials will be removed from the tunnel and NATM stabilization measures will be applied to secure unstable sections. In a second phase the entire tunnel will be lined with insitu concrete.

Realignment to avoid shallow cover hyrofracturing

Given the short construction period, work is planned to progress from several adits simultaneously with several forms applied for concrete casting.
Works will take place in the Chiriqui region, 25km from the city of David between Boquete and Gaulaca. The SELI team will join fellow SELI crews already working in Panama on the El Alto and Monte Lirio projects.
References
EPBM push in Panama - TunnelTalk, Feb 2011
Panama adopts EPC contracting for Esti scheme - TunnelTalk, June 2003

           

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