This was the finding of Dr. Salvador Reyes, a structural engineering expert flown in from Manila to look into the collapse of part of a 30-meter-high excavation wall in the Taft Property condominum project site in Cebu City.
His finding was contained in a report titled Evaluation on the Geotechnical Conditions of Taft Property’s Horizon’s 101.
The real estate company, which is owned by Cebu investors, is undertaking a 60-day rehabilitation plan to restore the collapsed area where at least 29 houses were affected.
(See 7-Step Solution table)
Reyes, a professor of UP Diliman-College of Engineering, specializes in geotechnical and structural engineering.
The presence of a creek in the project site was apparenlty overlooked, said Alvin Santillana, head of the Cebu City disaster risk reduction office.
He said the Manila-based contractor told him there was no waterway there, “but we can seen in the map of the GIS (satellite-based Geographic Information Service) that there is a natural waterway passing inside the property.”
At his office, Santillan showed an aerial photo provided by GIS that showed the creek in the project site. The aerial photo was taken in 2009 or 2010 before the excavation of the Taft Property along General Maxilom Avenue.
“There’s a creek that goes out to the ABC Liner terminal in Rahman Street in barangay Cogon-Ramos going to Echavez,” he said explaining the soft ground.
He said the water catchment is in the Theres’s College campus across the planned condominum site. He described the campus as a valley-like struck where water runs through it and passes an underground culvert.
Under the grounds of STC is an “imburnal” where the water enters, he said.
“There’s water there, they just diverted it.”
For now, he said, the contractor of Taft Property has to focus on restoring the damaged portion where at least 29 households nearby are affected “and ensure that if people move back there, the area is safe,” Santillana said.
“The mayor specifically instructed me to ensure that safety and security at the area is maintained by Taft and for Taft to accommodate the basic needs of those affected since they were the ones who caused discomfort to this people.”
A 15-meter buffer zone around the caved-in area was declared off limits to people after Tuesday’s collapse.
On the first day, 24 policemen were fielded in shifts to keep peopleout.
Santillana noted that the contractor of the excavation work who made the slope protection or wall was from Manila.
“They had no one from Cebu who was familiar with the area. Definitely it you’re from Cebu, you would know there used to be a waterway there.”
“Residents here know the soil is pond-like, meaning if you put your feet in it, it’s difficult to get out. It sticks, like quicksand.”
An investigation is underway by the Office of the Building Official (OBO), City Hall engineers and some contractors.
Residents in the buffer zone were evacated. Santillana said they have identified 29 households that will be trasnferred to pension houses at the cost of Taft Property.
Remedial steps and engineering methods will be used to restore the area but houses close to the edge of the excavation “might be affected.”
“It’s natural that during a construction, naay mobigay (something has to give way),” he said.
“On my own assessment, they didn’t look at the history of the place,” he said, where Taft Property plans to build two condominiums as the tallest in Cebu City. Currently work is focused on the first 50-storey tower
Asked if the site is suited for a high-rise strucutre, Santillana said yes “if they don’t economize or scrimp in the materials used.”
He said the slope protection or concrete wall that collapsed “might not be suitable for a very tall structure because there’s a creek, with soft clayish soil.”
Office of the Building Official chief Josefa Ylanan said the site is suited for a high rise structure depending on how it is planned and executed according to proper engineering methods.
She said OBO agreed with Taft Property’s corrective steps
“It was accepted yesterday that there were lapses.”
“Wala makita nga basa ang yuta” (They didn’t see that the soil was wet.) /Tweeny M. Malinao, Correspondent
7 STEP SOLUTION
||Berm the remaining soil; soil nailing and surface concreting resume water and electricity connections in the affected areas.|
||Install a 12-meter soldier pile made of steel; move back residents on the second line|
||Install tie-back anchorages|
||Connect the soldier piles to the tie-back anchors.|
||Backfill the back portion of the soldier piles. Evaluation and preparation of the repair works for the affected houses.|
||Construction of new walkway. Repair the affected houses on the first line|
||Back to houses and affected residents|
Source: Taft Property Venture Development Corp.