A chemical spill kept Owairaka residents indoors on Tuesday morning. At about 5.30am workers on the billion dollar Waterview tunnel project discovered a 1000 litre container of hydrochloric acid inside an industrial building on Hendon Ave had been punctured, leaking its contents and creating an acidic cloud. Hydrochloric acid is colourless but is corrosive and can burn. Fumes from the spill drifted towards Methuen Rd, Batkin Rd, Bollard Ave and New Windsor Rd. Residents were advised to stay indoors and some were evacuated. Police and multiple fire crews attended. Caustic soda was applied to the acid at around 11am to neutralise it.