[...] authorities are concerned about the health and environmental risks posed by debris contaminated by oil, asbestos and medical waste sitting on the seafloor off the coast and in 32 unregulated dump sites around the city. "Unsafe disposal of waste will cause further environmental damage in the long term," said Kuntoro Mangkusubroto, who headed the Aceh and Nias Reconstruction and Rehabilitation Agency, which led the massive clean-up effort and was dissolved in 2009 after the job was judged finished. Banda Aceh, located on the northern tip of Indonesia's Sumatra island, was the hardest hit city by the disaster, which devastated hundreds of communities in more than a dozen countries around the Indian Ocean. For weeks, the streets were strewn with rubble, and rescue workers retrieved dead bodies from under houses and in ponds, said Abdul Mutalib Ahmad, who worked at Banda Aceh's only landfill and witnessed the tsunami from atop a three-story building. Three months after the tsunami, the UNDP started a $40.5 million recycling program that employed 400,000 temporary workers to pluck wood and stone from the rubble and use the materials to rebuild roads and houses as well as to make furniture. The UNDP's Tsunami Recovery Waste Management Project cleared about 1 million cubic meters (1.3 million cubic yards) of debris from the city, enough to fill 400 Olympic swimming pools. [...] the mounting tsunami rubbish was cleared.