The Department of Environment and Natural Resources (DENR) on Thursday explained how sanitary landfills are designed and managed, as response operations continue following the fire at the Navotas Sanitary Landfill.

Environment Management Bureau (EMB) Solid Waste Management Division chief Maria Delia Cristina Valdez said sanitary landfills are engineered facilities built to minimize environmental impact through strict controls in design, operation, and maintenance.

Key features include base liners, daily soil cover, leachate collection and treatment systems, and gas management systems to ensure safe waste containment.

Valdez warned that improper waste disposal, such as open dumpsites, can lead to groundwater contamination, toxic emissions, and the spread of disease.

She said decomposing waste produces leachate, a liquid that can seep into the ground and contaminate water sources if not properly managed. In sanitary landfills, leachate is collected and treated before being discharged.

The briefing comes amid concerns over the Navotas Sanitary Landfill, which caught fire and burned for nearly three weeks, affecting air quality in parts of Metro Manila.

EMB National Capital Region officer-in-charge regional director Janice Pammit said soil compacting, covering, and cooling operations remain ongoing as of 29 April.

Thermal scanning using drones is being conducted to monitor subsurface temperatures and assess whether affected areas are cooling, as well as to evaluate response measures.

The agency is also issuing daily Air Quality Index advisories to inform the public and provide health guidance.

Pammit said response efforts have been strengthened with technical assistance from the Japan International Cooperation Agency, in coordination with the Bureau of Fire Protection, the Navotas local government, and the city’s disaster risk reduction office.

She said responders are using a phased approach to suppress the fire, beginning with stabilizing the landfill slope.

“The first task carried out was to stabilize the slope. Because if air enters the slope, it can reignite the fire in the subsurface,” Pammit said.

She added that JICA experts stressed the importance of limiting oxygen intrusion to prevent underground fires.

Pammit said responders were also trained on proper soil covering, compaction, and cooling techniques to manage heat buildup.

“The equipment also needs to be cooled down every 15 minutes or so. Otherwise, it could generate additional heat,” she said.

The EMB has also held talks with landfill operator Phil Ecology Systems Corp. following the incident. Pammit said the company has committed to submit required documents and provide additional soil cover.

She stressed that proper soil covering is critical in both landfill operation and closure, noting that minimum thickness requirements must be met to ensure environmental safety.