Dela Cruz said subterranean channels are natural drainages where rainwater is supposed to flow. If this is filled with soil or trash water, it will flow back, resulting to flooding and landslides when soil is saturated.
He said this explains why floods always occur at the City Camp lagoon, despite the construction of a drain tunnel.
According to Dela Cruz, there are numerous natural drainages at City Camp but because there were filled with soil, floods naturally occurred.
He said this also reason why Baguio got flooded at the height of typhoon Feria in 2001. The natural drainages were filled to give way to the construction of buildings.
Made up mostly of limestone, tunnels in Baguio are natural. Dela Cruz said this is why the whole of Baguio is considered a geologic hazard and construction of buildings must undergo a thorough soil study before construction proceeds.
He said this could have avoided the collapse of some houses because of the caving-in of tunnels.
To avoid this, Buildings and Architecture Office head Engineer Oscar Flores said for buildings that are three storeys or higher, a soil test that contain information such as soil pressure test, the extent of diggings to be done and a study showing the presence or absence of aquifers are first required from developers before building permit is issued. (RO)
