Naga, Cebu execs informed of landslide-prone areas as early as 2008

Landslide-hit Sitio Sindulan in Barangay Tinaan in Naga City, Cebu, has been classified as having "moderate landslide susceptibility" as early as 2008 by the Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources.

This contradicts the claim of Mayor Kristine Vanessa Chiong that the site of the September 20 landslide was never described as landslide-prone by experts, even following an inspection conducted by MGB Region 7 (MGB-7)

Based on documents obtained by GMA News Online, MGB-7 conducted a Geohazard Mapping in Barangay Tinaan, including Sitio Sindulan, on August 28, 2008.

With this, the agency classified Barangay Tinaan as having moderate landslide susceptibility and recommended that residents located at the footslope of the active area in Sitios Sindulan and Taylorville be relocated. However, there was no relocation site identified for the affected residents in Sitio Sindulan.

In Sitio Taylorville, relocation was recommended for some households in an area identified to have a steep slope. A relocation site was identified at the Philippine National Railway in Sitio Lower South, Barangay Tinaan.

Barangay Tinaan was identified as having "high susceptibility" to flooding.

At least 300 households along Pangdan River will be affected in a possible flooding that may reach neck-deep or one meter especially during heavy rains, and that flooding could be aggravated during high tide when seawater enters the river.

The agency further observed that the river bed is already shallow.

The MGB Central Visayas regional office then recommended the dredging and riprapping of low-lying rive banks and to monitor the progress of mass movement and presence of mass movement such as landslides and tension cracks.

The MGB-7 also recommended the development of an early warning device system and the identification of an evacuation site.

GMA News Online has contacted the local government of Naga City but it has yet to respond as of posting time.

Advisory on Typhoon Ompong

Before Typhoon Ompong hit northern Luzon earlier this month, MGB-7 sent a Threat Advisory to the Office of Naga City Mayor.

A joint follow-up Investigation Assessment on the cracks/fissures in limestone within Apo Land and Quarry Corp. (ALQC) Tenement in Sitio Tagaytay, Barangay Tinaan, was conducted two days before the September 20 landslide.

On September 19, the city administrator addressed to National Grid Corporation of the Philippines (NGCP), telling them that "in coordination with the Mines and Geosciences Bureau, and APO Land Quarry Corp (ALQC), [they] are currently monitoring the ground cracks/ fissures found in sitio Tagaytay, barangay Tinaan."

Past landslides

On May 31, 2011, a landslide occurred at the foot slope of a mountain located across Pangdan River, on the left side of the road going to Toldeo City in Sitio Tagaytay in Barangay Tinaan.

A rockfall, which  hit four houses, was attributed to the lithology or characteristics of the rock formation that is "inherently porous coralline limestone," and the very steep slope, and heavy rainfall prior to the incident, according to the MGB documents.

"Some residents also reported seeing cracks on the area near the ridge. The overhanging slab left by the recent rockfall still poses an imminent threat to the residents down the slope," the agency said.

MGB-7, again, recommended evacuation and permanent relocation of the residents of 26 houses located along the foot slope and continued observation for tension cracks and fractures on a "regular/ daily basis especially during the rainy season."

The agency also noted that the “temporary” relocation site is located on the floodplain of Pangdan River and is "susceptible to flooding."

By June 2011, a copy of the "Geohazard Investigation of the Reported Landslide Incident in Barangay Naalad, City of Naga" was given to the Barangay Chairman of Naalad, then-Naga City Mayor Valdemar Chiong, DENR Regional Executive Director Maximo Dichoso, and MGB Acting Director Leo L. Jasareno.

Threat advisories

In 2011 alone, MGB-7 issued landslide threat advisories to officials of Barangays Mainit and Cabungahan, as well as Flooding Assessment and Mapping to Barangays North Poblacion, East Poblacion, Colon, Mainit, Naalad, and Tinaan.

Geohazard Threat advisories were also sent to incumbent Mayor Kristine Vanessa Chiong on November 27, 2017,  August 13, 2018, and again on August 22, 2018.

It was on August 29, 2018, that the MGB-7 conducted a Geological Investigation/ Assessment on the cracks/ fissures in linestone within ALQC Tenement in Sitio Tagaytay, Barangay Tinaan.

In this particular inspection, the agency found that "[f]racturing of the materials is a natural phenomenon. It happens and will always happen in different locations and elevations and at different rates and scales, and with or without mining operations, and with or without vegetation."

Recommendations included continuous close monitoring during times of heavy rainfall and longer rain periods, comprehensive study of the area and close coordination and open communication with local government units.

ALQC was advised to conduct an Information Education Campaign (IEC) to allay the concerns of the residents.

ALQC has denied conducting quarrying operations at Sitio Tagaytay, Barangay Tinaan, but admitted that there was a road development at the area near the barangays hit by the landslide.

In the run up to the landslide that occurred early morning September 20, the MGB-7 sent the following documents:

• Aug. 29, 2018 — “Geological Investigation/ Assessment R: Cracks/ Fissures in Limstones within Apo Land and Quarry Corporation (ALQC) Tenement in Sitio Tagaytay, Barangay Tina-an, Naga City, Cebu” sent to ALQC Quarry Leader Engr. Romeo P. Igot. Transmittal letter signed by Atty. Gerardo V. Mahusay, In-charge of the Office of the Regional Director at the time.
• Aug. 29, 2018  — “Geological Investigation/ Assessment R: Cracks/ Fissures in Limstones within Apo Land and Quarry Corporation (ALQC) Tenement in Sitio Tagaytay, Barangay Tina-an, Naga City, Cebu” sent to Naga City Mayor Kristine Vanessa Chiong. Transmittal letter signed by Atty. Gerardo V. Mahusay, In-charge of the Office of the Regional Director at the time.
• Sept. 4, 2018 — A copy of the above-mentioned report was again furnished to the Office of the Mayor. The transmittal letter was signed by MGB-7 Regional Director Loreto B. Alburo. "
• Sept. 13, 2018 — Threat Advisory sent to the Office of Naga City Mayor at the onset of Typhoon Ompong. Email sent at 12:58 p.m. Another email sent 1:52 p.m.

Following the September 20 landslide, Environment Secretary Roy Cimatu fired top officials of the MGB-7 and ordered a  temporary stop on all quarrying activities in at least eight regions. —KBK, GMA News