At 12 midday on Friday 25th June, Changuinola 1 Dam in Panama reached full capacity and started spilling after 33 days filling at an average inflow of 127 m³/s.

By chance, first filling of the dam coincided with the arrival of a small flood.  In view of the fact that the designer’s had requested that the build up in discharge on the chute and flip-bucket spillway be filmed and that the most interesting period was anticipated to be during the night, the site team set up some lighting on the spillway and beneath the flip bucket.  Before dawn the next morning, the early risers were greeted by the impressive sight of a substantially higher discharge than had been anticipated and the opportunity was taken to take some impressive photos.

 The flood discharge peaked at 6 am on the Saturday morning, with 412 m³/s cascading over the dam wall, at a maximum spilling depth of 1.25 m.

Impoundment at Changuinola 1 Dam in Bocas del Toro, Panama commenced on 22nd May, with closure of the two 9m x 9m river diversion culverts. Changuinola 1 Dam is the first RCC arch/gravity dam in the world to be brought into operation outside South Africa and China. The 105 m high dam contains approximately 895 000 m³ of RCC.

Frequent and heavy rainfall was probably the greatest of many challenges on site, where 15 days on which rainfall is recorded is considered a “dry” month and 26 days, a “wet” month. Over 450 mm of rain was measured in August 2010, while the highest monthly RCC placement rate for the project of 120 000 m³ was achieved in September 2010 despite 261 mm of rain spread over 21 days.

Changuinola 1 Dam was constructed with a high strength, low Vebe time, paste-rich, super-retarded RCC that ensures seamless concrete. Instrumentation installed has reflected very good performance for the RCC, which did not indicate any signs of creep under the early hydration temperature rise.

Work on the 4 km headrace tunnel and the 200 MW power station progressed steadily and the completion of the project will bring urgently needed additional electrical power to the southern-most country of central America, where many towns currently rely on diesel generators.

ARQ was involved in the project from the EPC feasibility stage and designed directly for the contractor as the project implementation progressed. Several of ARQ’s staff spent time on site during the course of the project and we now eagerly anticipate filling to capacity during early July 2011.

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