How was the water supply disrupted?
The water is believed to be contaminated by Indulin AA86, an asphalt emulsifying agent.
The chemical seeped into the water during a backflow incident — when water flows in the opposite direction — in the industrial district of Corpus Christie. A faulty valve triggered the incident.
"In the simplest terms, someone was careless when they were injecting chemicals with a pump and (...) when the injection occurred it crossed over into our water system," city spokesperson Kim Womack told KRIS-TV, a local TV station.
Can the contaminating chemical harm people?
Indulin AA86 is a viscous, dark amber liquid that is used to combine different substances, particularly asphalt with water. It is hazardous on its own or when it comes into contact with water as it is an insoluble substance.
Exposure can lead to skin irritation, a burning sensation in the eyes, and damage to the respiratory tract and digestive system.
How are people getting water?
Residents have been advised to use only bottled water and avoid tap water for their daily needs.
They have been cautioned against treating tap water since "boiling, freezing, filtering, adding chlorine or other disinfectants, or letting the water stand will not make the water safe."
Some schools in the city have been closed. Those which remain open are providing bottled water and antibacterial sanitizer as long as supplies last.
The water ban has been lifted from certain neighbourhoods in the city. Other residents are still waiting for free-flowing clean water.
Has anyone been held responsible?
Two restaurants have obtained a restraining order against Valero Energy, an oil manufacturing company, and Ergon Asphalt & Emulsions Inc, an asphalt production company. The order prohibits Valero and Ergon from destroying any evidence which shows they contaminated the water supply.
Valero has responded, saying that they do not believe that the city's water supply was affected. "We do not believe this issue is being caused by Valero's Corpus Christi refineries," Valero spokesperson Lillian Riojas said made in a statement to the Corpus Christi Caller-Times.
Has this happened before?
The city has a history of poor water infrastructure. The cast iron pipes carrying the city's water are 362 kilometres long and were built between 1950 to 1959. Plans to rebuild the pipes, drafted in 2015, are costly.
Three water advisories have been issued since 2015, one of them over E.Coli concerns in July last year.
Another advisory in September 2015 warned of low chlorine levels. The third was in May 2016, over the presence of non-harmful bacteria.
The town of Flint, Michigan recently suffered from the contamination of lead in their water supply.