levy a carbon tax on its largest carbon-emitting corporations producing more than 25,000 tons of carbon dioxide per year, at $5 per ton. To reduce the country's dependence on fossil fuels, it has ramped up deployment of solar panels on rooftops and vertical surfaces of buildings, and other initiatives like building one of the world's largest floating solar farms at Tengeh Reservoir in Tuas. Water supply Singapore considers water a national security issue and the government has sought to emphasise conservation. Water access is universal and of high quality, though the country is projected to face significant water-stress by 2040. To circumvent this, the Public Utilities Board has implemented the "four national taps" strategy – water imported from neighbouring Malaysia, urban rainwater catchments, reclaimed water (NEWater) and seawater desalination. Singapore's approach does not rely only on physical infrastructure; it also emphasises proper legislation and enforcement, water pricing, public education as well as research and development. Singapore has declared that it will be water self-sufficient by the time its 1961 long-term water supply agreement with Malaysia expires in 2061. However, according to official forecasts, water demand in Singapore is expected to double from 380 to 760 million US gallons (1.4 to 2.8 billion litres; 1.4 to 2.8 million cubic meters) per day between 2010 and 2060. The increase is expected to come primarily from non-domestic water use, which accounted for 55% of water demand in 2010 and is expected to account for 70% of demand in 2060. By that time, water demand is expected to be met by reclaimed water at the tune of 50% and by desalination accounting for 30%, compared to only 20% supplied by internal catchments. Singapore is expanding its recycling system and intends to spend $7.4 billion (Sg$10 billion) in water treatment infrastructure upgrades. The Ulu Pandan wastewater treatment was specially built to test advanced used-water treatment processes before full deployment and won the Water/Wastewater Project of the Year Award at the 2018 Global Water Awards in Paris, France. Operation started in 2017 and was jointly developed by PUB and the Black & Veatch + AECOM Joint Venture. Transport Land Singapore has a road system covering , which includes of expressways. The Singapore Area Licensing Scheme, implemented in 1975, became the world's first congestion pricing scheme, and included other complementary measures such as stringent car ownership quotas and improvements in mass transit. Upgraded in 1998 and renamed