Case History on Defined Sump Floating Cover System MWD Southern California Skinner Water Treatment Plant

摘要

As part of a potable water reservoir project for the Metropolitan Water District ofSouthern California, Layfield Environmental Systems fabricated and installed aflexible geomembrane defined sump floating cover system. On this project Layfieldoperated as the general contractor with a scope of work that included removing andreplacing the existing floating cover and installing a new 65,000 m2 (700,000 ft2)floating cover system. The project also included an additional 28,000 m2 (300,000ft2) of a chafer reinforcement material around the perimeter of the floating cover, rainwater removal pumps, upgrading of the existing electrical systems, installationof drain pipes, mechanical work and the design and operation of a temporary watertreatment facility.This project encountered some serious installation challenges including a tight 180day installation schedule as this was a critical reservoir with an operational capacityof 130.4 hectares (326 acre feet) providing treated water to Riverside and San DiegoCounties. A special consideration on this project was the requirement to capture allwater that was collected from the construction site. This included the design andoperation of a temporary water treatment facility as the Regional Water QualityBoard had set strict discharge limits on the water released from the site. The watertreatment plant was designed to capture nuisance chemicals or contaminants inrainwater as a result of construction.There was also major water leakage of up to 1,135 litres (300 gallons) per minuteat the influent and effluent gates requiring continuous pumping and dewateringstrategies throughout the duration of the project. The project was further challengedby excessive poor weather as part of an El Nino year in California. This paperdiscusses the various technical challenges and the innovative design and projectmanagement solutions incorporated to help finish the project on schedule.