MGB conducts geohazard assessment near mine site of OceanaGold
To assess the communities near the mining sites, the Mines and Geosciences Bureau Region 02 conducted a rapid geohazard and safety assessment in barangays near or adjacent to OceanaGold Philippines Incorporated particularly Brgys. Alimit and Didipio, Kasibu, Nueva Vizcaya on Sept. 24-27, 2018.
The said assessment was in line with the government’s efforts to reduce, if not totally mitigate the destructive effects and impacts of natural hazards to the community.
The technical team was composed of Geologists Chad Lowe S. Aquino and Jiles Arvin A. Vergara, Engr. Robert Carreon, and Senior Environmental Management Specialist Jose delos Santos.
According to their assessment report, the assessed areas were rated as having low, moderate, high, or very high critical susceptibility to landslides.
The areas assessed were only limited to sitios and puroks that are within or near the mine site of OGPI due to the limited amount of time for the assessment.
The technical team also prioritized the areas that were already identified in the latest geohazard assessment as danger zones.
Based on the 1:10,000-scale geohazard map produced in 2013, majority of the communitiees surrounding the OGPI mine site, including the mining area have moderate susceptibility to landslide, while the surrounding elevated areas where some puroks are situated have high susceptibility to landslides.
“This is due to the area being situated on a mountainous terrain with peak elevations ranging from 800 to 1100 meters above sea level and slopes that are moderately steep to very steep,” Geologist Chad Aquino said.
According to their report assessment, some of the portions of Brgys. Alimit and Didipio that are located near the rivers could still be prone to flash flood even though they are within landslide-susceptible areas.
Meanwhile, majority of the residential areas at Purok 1 in Brgy. Alimit where there is small-scale mining activity are located in low-lying areas.
“The eight households within this portion of the purok are situated downslope of the mining area,” Aquino said.
The old Barangay Health Center and Day Care Center also in Brgy. Alimit has a Very High Susceptibility rating while the abandoned/old small- scale mining area in Purok 2 has also a Very High susceptibility rating to landslide.
The quarry area for backfill materials on the boundary between Purok 2 and Purok 3 has also a High susceptibility rating to landslide.
“The road going to Alimit Elementary School in Purok 6 has also a Very High susceptibility rating to landslide which is very critical,” Vergara said.
According to the assessment report, there are tension cracks generally trending northwest-southeast parallel to the road that started in 2016 and has worsened in 2017. The team assessed that Sitio Dupit is Very High susceptible to landslide.
The road to high school in Sitio Pimmadek has also a Very High susceptibility rating to landslide where the portion of circumferential road is reported to continuously fail even after two times of repair and reconstruction.
Further, the Eastern Nueva Vizcaya National High School is also assessed as having a Very High susceptibility rating.
“Based on the existing 1:10,000 scale landslide and flood hazard map, the area where the National Highschool is situated has a moderate landslide susceptibility, but due on the observed evidences of an impending mass movement, we assessed it as very critical, having a Very High susceptibility rating to landslide same with Didipio Elementary School,” Vergara emphasized.
Didipio Elementary School was also assessed as having a very high susceptibility rating to landslide.
The technical team also conducted a geohazard assessment in Sitio Surong where the small-scale mining hydraulic area is located. The team found out that hill where the small scale mining activity is located is already half mined/cut. The technical team said that this posed a great risk since it is altering a terrain that greatly reduces its structural identity.
“If there will be an event that will trigger this area, for example a strong typhoon or an earthquake, this may induce failure,” Aquino said.
The team recommended for a strict and continuous monitoring of the areas to avoid further hazards. -With Reports from Geosciences Division