Tongonan

Tongonan geothermal field in Leyte consists of two separate geothermal systems of Tongonan and Mahanagdong. The area was initially mapped in 1972 on a reconnaissance level. Subsequent exploration activites from 1970-‘s to 1980’s included geology, geophysics, and geochemistry surveys, as well as drilling of shallow and deep exploration wells.

The Tongonan geothermal system in the north is a fine example of a water dominated system associated with andesitic volcanism. The resource covers about 16 square kilometers area. The center of the resource at Mahiao sector hosts fluids with temperature of more than 300 degrees Centigrade. The major outflow towards Malibog sector in the south has temperature of up to 240 degrees Centigrade. Impressive thermal features manifests along Bao River, situated further south of the resource.

Mahanagdong geothermal system is also a water-dominated system covering 10 square kilomenters area. The center of the resource also has temperature of 300 degrees Centigrade. The outflow sector has temperature of 250 degrees Centigrade. Aside from deep fluids, there are other type of fluids such as the acidic and cooler fluids in north which constantly pose constrains in field development and production. Full development of Tongonan geothermal field was made possible through a build-operate-transfer scheme (BOT) initiated by EDC. There are three phases of development program: Leyte-Samar, Leyte-Cebu, and Leyte-Luzon grid interconnections.