Water drawn from Las Virgenes Reservoir is filtered and disinfected again at LVMWD's Westlake Filtration Plant, built in 1989. In operation mainly during the summer, it is capable of processing 15 million gallons per day (MGD). Water is pumped from the base of the dam to a clear well tank and then enters the plant for filtration. Using 10 diatomaceous earth (DE) filtration units, each basin can filter 1.5 MGD. Once filtered, the water is disinfected using chloramines (chlorine + ammonia). Disinfection kills bacteria and prevents bacterial growth in the distribution system.