Cebu City Vice Mayor Tomas Osmeña questioned whether Monterrazas’ detention facilities can contain water from an extreme rainfall event during the Sept. 15 City Council session, citing a required capacity of 26,701 cubic meters, a current capacity of 62,710.5 cubic meters, and an estimated demand of at least 300,000 cubic meters.
Developer Mont Property Group told the council that Monterrazas has 24 operational detention ponds across the 118.4-hectare development with a current capacity about 235 percent of the requirement, while Osmeña based his 300,000-cubic-meter figure on historical rainfall over the property's roughly 1.18 million square meters.
The City Council referred the Technical Infrastructure Committee report back to committee to clarify the engineering basis for the required figure, the design storm used, how the 62,710.5-cubic-meter capacity was calculated, and how the system handles major rainfall, with no review timeline set.
CEBU City Vice Mayor Tomas Osmeña has questioned whether Monterrazas’ detention facilities can contain water from an extreme rainfall event, pitting the project’s reported storage capacity against his own calculation based on historical rainfall.
At the Sept. 15 City Council session, Osmeña cited three figures: 26,701 cubic meters as the required detention capacity per the Technical Infrastructure Committee (TIC) report, 62,710.5 cubic meters as current capacity, and at least 300,000 cubic meters as what he said an extreme event demands.
Reported capacity vs. required capacity
Monterrazas has 24 operational detention ponds serving 14 catchment areas across the 118.4-hectare development, developer Mont Property Group told the council. Its current capacity is about 235 percent of the requirement; 13,520 cubic meters in proposed additions would bring the total to 76,230.5 cubic meters.
Historical rainfall as basis for higher demand Osmeña based his 300,000-cubic-meter figure on historical rainfall over the property’s roughly 1.18 million square meters. Pagasa Visayas’ Al Quiblat, in an earlier interview, said typhoon Ruping produced 200 millimeters (mm) of rain in 1990 versus Tino’s 183 mm in 2025, a gap he attributed to urbanization and drainage loss rather than rainfall alone.
Osmeña calculated that a Ruping-scale event could dump about 319,000 cubic meters on the site, which he compared against both capacity figures.
“If they are going to put detention ponds, they have to increase the capacity to 300,000 cubic meters have drainage so you can pump it out,” Osmeña said, urging the council to weigh a cease and desist order pending further review.
That comparison does not by itself settle how much storage is needed. Not all rainfall becomes runoff requiring simultaneous storage; the actual figure depends on drainage layout, infiltration, land cover and the storm design standard used.
The TIC report, which recommended letting the project proceed after a joint inspection with city offices, does not appear to address Osmeña’s benchmark directly, and no independent engineer has publicly weighed in on which storm standard should apply.
Design questioned
Osmeña also disputed the developer’s use of the June 3 rainfall, just 4.2 mm per Pagasa, as proof the drainage works, and criticized the ponds’ elevated, sand-embankment design for lacking a pump-out mechanism, unlike Bonifacio Global City’s underground system in Taguig.
The developer said its terraced ponds let water move gradually between basins as each fills; the mayor’s chief of staff, Kenneth Siasar, said this allows runoff to release gradually downhill.
Councilor Harry Eran asked which office set the 26,701-cubic-meter requirement. The council referred the TIC report back to committee to clarify the engineering basis for that figure, the design storm used, how the 62,710.5-cubic-meter capacity was calculated, and how the system handles major rainfall. No review timeline was set. / CAV