Geologists from the Mines and Geosciences Bureau (MGB) and the Department of Public Works and Highways (DPWH) reiterated the clear and present danger in stressing out and pressuring the absorptive capacity of Shrine Hills.
“Shrine Hills that area is red, it is highly susceptible to landslides,” MGB Geology Division Chief Beverly Mae Brebante told councilors when asked about the Hill’s classification in the geo-hazard map at Tuesday’s regular session.
“The road widening may have triggered the mass movement in the area. The presence of spring may have contributed to the weakening of the slope due to the saturation of the soil, spring was already present prior to road widening activities,” she said.
“Aside from the excavation of DPWH, the primary reason for the landslide was the development which occurred outside the department’s project units which is above the slope,” DPWH geologist Thea Shaira Mae Peguit said.
Peguit said based on the history of Shrine Hills, that area is, in Geology parlance, a “landslide escarpment.” Research shows this means a significant quantity of material has already fallen in the form of landslides.
“There was already an old landslide, so the development we see now from 7th Day Adventist and private properties was old landslide debris. And since it was standing on landslide debris it was already weak,” she said. The diversion of waterway, which did not have a government permit, caused additional weight and became the driving force of the landslide, she added.
Brebante said MGB keeps on reassessing the geo-hazard map even if Shrine Hills is already classified as a red zone because the map is dynamic and needs to be adjusted.
MGB is mandated to provide geological studies which are used as the basis for an in-depth study for the implementation of various projects such as the DPWH in its road construction projects.
Brebante said MGB has recommended several mitigating measures to DPWH such as a lower slope angle, application of riprap or the use of Gabions. Gabions, which is a welded wire mesh, is considered an efficient and cost effective way to manage erosion and retain soil sustainably.
MGB initially detected the crack at Shrine Hills last September 30 and they immediately dispatched one geologist to inspect the area. This was immediately reported to the City Disaster Risk Reduction Management Center and the DPWH. Lovely A. Carillo