Environmental officials held a technical session Thursday to detail the engineering principles of sanitary landfills as recovery efforts continue at the Navotas Sanitary Landfill, which burned for nearly three weeks.

The fire, which broke out earlier this month, has significantly impacted air quality across Metro Manila, prompting the Department of Environment and Natural Resources (DENR) to deploy specialized monitoring and suppression techniques.

Maria Delia Cristina M. Valdez, chief of the Environmental Management Bureau (EMB) Solid Waste Management Division, said sanitary landfills rely on engineering controls — such as base liners, leachate collection and gas management — to prevent the environmental hazards associated with open dumpsites.

“Proper waste disposal planning is crucial,” Valdez said. She cited that without these systems, decomposing waste produces leachate that can contaminate groundwater and toxic emissions that threaten public health.

In Navotas, response teams are currently focusing on soil compaction and cooling operations. Janice R. Pammit, officer-in-charge regional director of DENR-EMB National Capital Region, said authorities are using drones equipped with thermal scanners to monitor subsurface temperatures and evaluate the effectiveness of their interventions.

The disaster response has been bolstered by a relief team from the Japan International Cooperation Agency (JICA). The Japanese experts provided technical guidance to the Bureau of Fire Protection and the Navotas local government, specifically on managing underground fires.

Pammit said the immediate priority was stabilizing the landfill’s slope to prevent oxygen from reaching the subsurface.

“If air enters the slope, it can reignite the fire in the subsurface,” Pammit said. She added that ground crews must cool their equipment every 15 minutes to prevent additional heat buildup during the compaction process.