- Westminster Membrane Water Treatment Plant
Burns & McDonnell/Garney LLC was selected to provide design-build services for the new 15-million-gallon-per-day (MGD) Westminster Northwest Water Treatment Facility. The process design utilizes enhanced conventional treatment with plate settlers followed by microfiltration membrane units. This alternative was proposed by the design-build team to increase by 50 percent the allowable flux of the membrane units, which had been pre-purchased by the city. Plant piping is organized with the flexibility to bypass pretreatment and utilize the raw water pressure for direct microfiltration during periods of low turbidity in the raw water.
The design-build team also substantially modified the original building layout to produce a more cost-effective project. Originally, the city had a conceptual cost estimate of $18 million for a 10-MGD water treatment plant. As the project was at 30 percent design, the budget increased to approximately $27 million for a 10-MGD plant. With costs rising substantially, the City of Westminster decided to pursue a design-build procurement option and solicit proposals from prequalified firms. The Burns & McDonnell/Garney team was selected to design and construct the facility for a cost of $20 million at a rated capacity of 15-MGD. The unit price per gallon was reduced from $2.70 per gallon to less than $1.33 per gallon. As indicated by the City of Westminster, “The Design/Build team of Burns & McDonnell and Garney Construction is building a 15 million gallon per day (MGD) plant for 75 percent of what we had originally anticipated spending on a 10-MGD facility.”
The new Westminster plant was sized for a hydraulic capacity of 20 MGD and provides space to accommodate future process equipment. The membrane system was designed to utilize one skid for either secondary recovery or to recycle membrane backwash water to the pretreatment process. This allows the city to operate either in a high recovery mode or higher process flow mode incorporating flexibility into the system. The project design also included a 2-MG clearwell with a 15-MGD high service pump station (expandable to 20 MGD).
- Backwash water recycle
- Cost per gallon reduced from $2.70 to $1.33