The Lulu Island Wastewater Treatment Plant provides secondary treatment to wastewater from approximately 172,000 residents in Richmond, British Columbia. CWA was selected by Metro Vancouver to provide a method to individually isolate each of the five raw sewage pumps for periodic preventative maintenance.
The work area in the wet well is classified as a confined space with limited access, making safety for maintenance personnel a priority. To maintain the focus on safety, CWA held multiple safety review meetings focusing on the principle of prevention through design throughout the course of the project.
In order to safely isolate the pumps for maintenance, isolation gates on the suction side of the raw sewage pumps were required. The original frames, which were intended to act as the gates, were no longer suitable for isolating the influent pumps from the wet well and needed to be replaced with a safer and more convenient method. Furthermore, the new system needed to allow for regularly-scheduled maintenance and emergency repairs that would not alter the existing process functionality.
Other constraints required that the solution be readily available, affordable, easy to install, and quick to implement.
CWA produced a 3D model using 3D scan results and associated record drawings that were used to verify the arrangement of the existing wet well facility and associated equipment. The model of the 3D scan was inserted into 3D models of each concept to confirm model accuracy and check for interferences and other potential issues.
CWA presented two concepts to Metro Vancouver for review. The preferred solution consisted of five manually-actuated slide gates installed against an existing wall of the wet well that block each influent pump’s suction inlet when maintenance is required.
The criteria for the slide gate was identified and meticulously specified for this application. The gate component, materials, and design remained standard in order to provide a short lead time, reduced unit cost, and efficient installation. CWA also supplied construction and engineering capital cost estimates and a full tender package.