Semakau Landfill is filled mainly with ash produced by Singapore's four incineration plants, which incinerate the country's waste, shipped there in a covered barge (to prevent the ash from getting blown into the air) every night. Contrary to popular belief that Semakau Landfill would be another dirty and smelly landfill, the care put into the design and operational work at the landfill has ensured that the site is clean, free of smell and scenic. During construction, silt screens were installed to ensure that the corals were not affected during the reclamation works. The landfill is lined with an impermeable membrane, and clay and any leachate produced is processed at a leachate treatment plant. Regular water testing is carried out to ensure the integrity of the impermeable liners.