so the hot spring remained untouched and forgotten. Water properties According to local geologists, the exact source of the spring remains unknown, but it is believed that its origin may be southwest of its actual location, possibly at Bukit Timah. Hot springs are formed when underground water comes into contact with hot rock masses. The resulting high pressure causes the water to seep upwards through cracks, forcing itself out of the ground as a spring. A series of tests conducted by the PSB Corporation and SGS Testing & Control Services found the spring water contains 420 mg of chloride per litre, an amount which is substantially higher than the 35 to 100 mg in the water from Choa Chu Kang and Bedok waterworks. It was also found that the sulphide content is three times more than tap water and the spring water is also slightly alkaline due to the presence of minerals. Natural spring waters may have health benefits, similar to the hot springs of other countries near tectonic plates with volcanoes, in a search for cures for some skin conditions, as well as debilitating ailments like rheumatism and arthritis. Although local rheumatologists conceded that hydrotherapy is an accepted treatment that can be helpful for mild forms of rheumatism or muscle strain, they, along with dermatologists, remain skeptical of claims about the alternative healing of the natural spring water. Hot hard water bubbles continuously in the well, releasing a slightly unpleasant sulphur mud-like odour together with steam. The temperature of the spring water is measured by precision instrument to be constant . In an investigation carried out by the Nanyang Technological University in 1994, the hot spring was found to have an estimated yield of approximately per minute at ground level through installed steel casings. Land acquisition by MINDEF In 1998, the Ministry of Defence (Mindef) acquired the land containing the spring for the expansion of the nearby Sembawang Air Base, leaving F&N with less than 4 hectares (10 acres) of land. Its water-bottling plant survived until the early 1990s, however. In January 2002, local interest in the hot spring caught the attention of Singaporeans after the surrounding land had been cleared to begin the RSAF air base extension. Sembawang community leaders gathered signatures to petition Mindef, which was going to fence off the area, to preserve and develop the hot spring for the general public. Mindef gave the green