AWWA JAW18766

The Metropolitan Water District of Southern California recently placed floating covers on two of its finished-water reservoirs in order to improve the microbiological quality of the water. Since xylenes were used as a solvent during installation of the covers, health and aesthetic factors had to be considered before the reservoirs could be returned to service. Monitoring ensured that xylenes leaching from the covers were diluted to a negligible concentration in the effluent. Health requirements were satisfied, and no complaints about the aesthetic quality of the water were received. The bacteriological quality of the effluents remained high throughout the filling and returning to service of the reservoirs. Includes 18 references, tables, figures.