DEPARTMENT of Human Settlements and Urban Development-Davao Region (DHSUD-Davao) wants building developers to conduct soil testing to determine if it is a "sink hole"-prone area.
DHSUD-Davao officer-in-charge Miguel Palma Gil said his office is pushing the inclusion of a karst analysis, a study of a landscape formed from the dissolution of soluble rocks including limestone, dolomite and gypsum. He said it is characterized by sinkholes, caves, and underground drainage systems.
Currently, Palma Gil said requiring a karst analysis is not imposed in the National Structural Code of the Philippines.
He said it is important to include the analysis in the standard of building construction since monitoring the movement of the soil is hard to determine since it lies deeper.
He added developers in the Philippines, which is prone earthquakes, need to consider the karst feature of the area since sink holes are not easily detected.
Palma Gil said other countries are strictly imposing it, especially in first world countries like the United States and Japan.
"Karst analysis is very important because there are areas that need to be included, if it is a sink hole prone area or not," Palma Gil said, adding they will be coordinating with the Department of Environment and Natural Resource (DENR) in mapping these areas.
While there are no reported sink holes that opened up in the previous calamities in the city, he said the city should not be complacent.
He added the sinkholes would be a burden to both the developers and occupants if left unnoticed.
In a study conducted by the University of Texas, nearly all surface karst features are formed by internal drainage, subsidence, and collapse triggered by the development of underlying caves.
The study added rainwater becomes acidic as it comes in contact with carbon dioxide in the atmosphere and the soil. As it drains into fractures in the rock, the water begins to dissolve away the rock creating a network of passages.
Initially, Palma Gil had long proposed it before DHSUD was created, merging the Housing and Urban Development Coordinating Council (HUDCC) and the Housing and Land Use Regulatory Board (HLURB).
The official said he already sent a written proposal to the DHSUD board, but there was no response as of press time.
He said his proposal could "hopefully be pushed as a national directive."
He added it is part of upgrading the structural integrity of both building and the land area it will be built.
"These measures should be looked into and reviewed, and mamitigate ang effect if naa'y bagyo, linog, sunog or any other manmade or natural calamities. Maong naa mi reason to include this (We are strongly pushing these measures, which should be looked into and reviewed, in order to mitigate its effect in times of typhoon, earthquake, fire, and other manmade and natural calamities)," he said.