Mitigating the Impact of Landslide Hazards in PNOC-EDC Geothermal Fields

Abstract

Landslides and slope failure hazards are common in PNOC-EDC geothermal fields, which are located mostly in steep mountainous terrain. This situation is further aggravated by the presence of inherently weak clay-altered ground and sometimes fumaroles and mud pools above the slopes. From being mere road nuisances, these landslides had become an enormous threat to PNOC-EDC operations because these could cut-off pipelines, and even obliterate a geothermal well pad resulting to plant shutdowns thus, loss of revenue. Various approaches were implemented to address these hazards and were grouped into four main categories, namely: 1) avoidance, 2) protection/prevention, 3) acceptance, and 4) remediation. Some of the remedial measures that were carried out include benching, drainage control, structural barriers and vegetative stabilization. Prior to construct these engineering measures, a hazard assessment is first undertaken to properly address the problem. Regular audit and review of these remedial actions were continually made for each project sites creating checklists to comparatively assess if such measures were adequate. Additional hazard assessments were done if the works were inadequate and or if new slide prone areas were identified. For critical sites such as transmission towers, extensometers and tilt meters were installed for constant monitoring of any slope movement.