Five months after Los Angeles officials exclaimed “shade balls away” as they ceremoniously sent 96 million plastic orbs rolling into a reservoir, the four-inch pieces of high density polyethylene will be taken out of three of the four reservoirs where they have been used.
Federal rules call for all drinking water that is open to the air to be covered to prevent sunlight from triggering unhealthy chemical reactions with chlorine and to keep out rain, dust and birds. Shade balls will continue doing the job at the massive Los Angeles Reservoir, which also has a secondary ultra-violet treatment process to disinfect the water.
However, the shade balls will be removed from the other reservoirs. One reservoir is being taken out of service and the other two will get non-permeable floating covers because they do not have a back-up UV treatment process.
The LA Reservoir has a 175-acre surface and it would have been cost prohibitive to blanket it, Ellen Cheng, a spokeswoman for the Los Angeles Department of Water and Power, said in a telephone interview. In that case, the shade balls, which cost about $34.5 million, represented a savings of about $250 million.
“We're very happy with the shade balls for their cost and effectiveness for our large reservoir but for the smaller ones — because of the regulation about open reservoirs — we're continuing to comply by making sure that in places where we can have a non-permeable cover that we do that,” Cheng said.
Open-air reservoirs for drinking water have to be covered to stop a potentially dangerous chemical reaction between bromide, which occurs naturally in groundwater, and chlorine, which is used as a disinfectant. Sunlight turns the mix of bromide and chlorine into bromate, which is a suspected carcinogen.
L.A. a shade ball pioneer