A tanker truck spilled 25 tons of caustic soda (sodium hydroxide) into a municipal reservoir for the city of Hancheng in Shaanxi province on Friday. (NY Times/AP 8/27). As a result the water supply for about 100,000 people in the city (total population about 400,000) was cut off for 2 days. After neutralizing with some 10 tons of hydrochloric acid, the water supply was restored on Sunday.