Rebuilding filters from the ground up at one of the largest treatment plants in the country

Weymouth Water Treatment Plant Filter Rehabilitation

Some of the filters at the Weymouth Water Treatment Plant were over 70 years old, so the Metropolitan Water District of Southern California (Metropolitan) had a goal to build robust, rehabilitated filters that will last more than 50 more years. At the time, this was one of the largest filtration projects in the United States.

Initially, we supported Metropolitan in a 2.5-year full-scale trial of different filter arrangements. Following this study, our team was engaged for the full rehab design which was constrained by shallow existing filter boxes and effluent piping configuration. To make it work in limited available height, we reconfigured troughs and gullet walls and selected a low-profile underdrain system with a media retaining plate. We did a detailed hydraulics analysis to define the operating range of the filters and effluent channel which gave plant operators new insights into phenomena they had observed in practice.

The final design required intimate familiarity with the facility, custom engineering, engagement of Metropolitan operators, and attention to construction sequencing to allow for continuous operation. All 48 rehabilitated filters are now back in service and operating to Metropolitan’s satisfaction.