The L.A. Department of Water and Power officials announced on Friday that 600 million gallons of water will be drained from the Elysian and Silver Lake reservoirs, due to high levels of chemicals that can cause cancer apparition.

The reservoirs will be out of use for three to four months next year, between June and October. Officials announced that the water will be used for other activities that don’t involve human consumption.

According to the Department of Water and Power, the reservoirs have been put out of service two days after the problem was depicted; still they have been highly criticized for not making a public announcement on the matter.

“I praise the swift and quick reaction of the DWP, but I don’t like how long it took the residents of Silver Lake to find out about it […] The ratepayers deserve full information when public health is concerned,” said City Council President Eric Garcetti (Los Angeles Times).

DPW officials said however that they did not wish to go public with the information until they fully understood the nature of the problem. The rest of the reservoirs have immediately been tested and declared safe for human consumption.

The high levels of carcinogen bromate found in the water came as a result of an unusual combination between intense sunlight, the natural bromide in the water and chlorine, used for eliminating the bacteria.

The approximately 600,000 consumers have been exposed to a minimal dangers, say the DWP officials. According to them, the bromate creates a small cancer risk only if consumed daily over a lifetime.

The announcement on the two reservoirs to be drained comes in the middle of a prolonged drought for which Mayor Antonio Villaraigosa already stated the conservation necessity. But the DWP doesn’t consider this to be a major problem, considering that the two reservoirs account for less than 1% of L.A.’s annual water consumption.