消壓塔 Pressure Relief Tower
Ascending the Guanyinshan Trail in Gongguan, visitors can see a row of four "Chemical Control Tanks," which were formerly used to store purifying chemicals used to sanitize the drinking water. These tanks were built on higher ground so that the chemicals could be injected by gravitational force into the raw water, where they absorbed/eliminated the particles causing turbidity in the water and filtered harmful sludge and bacteria, purifying the water and increasing its safety. These tanks were built in 1971, and retired in 1977 due to the relocation of the water-intake unit to the Qingtan Dam.