An explosion demolished a thin rock wall that separated two sections of a tunnel Thursday, thereby advancing the Proyecto Hidroeléctrico Reventazón in Siquirres, Limón.
The person pushing the button was President Laura Chinchilla, but the heroes of the day were the 400 workers who had carved the 1,350 meters (4,429 feet) of tunnel. It is the tunnel with the biggest diameter in Costa Rica.
Workers on either side of the blast climbed over rubble to congratulate members of the opposite crew.
The power project will produce 305.5 megawatts of electricity sufficient for 525,000 homes, said the Instituto Costarricense de Electricidad.
Excavation crews removed 106,000 cubic meters (138,642 cubic yards) of rock. Officials said the tunnel will be ready to go into service in the first few months of 2012.
Although there are 400 persons working on the tunnel, the workforce at the site number 1,700. Also being constructed is a dam to hold back the Río Reventazón. The dam is to be 130 meters (427 feet) high and 527 meters (1,729 feet) long. The water diverted into the tunnel at the dam will turn four turbines at the other end.
The electrical institute said that an archaeological survey has been completed on the 200 hectares (494 acres) that will be inundated by the dam.
About 60 percent of the total workforce in the canton of Siquirres is on the job for this project, the institute estimated.