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166 www. bus- ex. com August 09 of the wastewater as possible. Then about half of the year the wastewater is chlorinated before it's discharged into the ocean outfall. " We get a pretty good removal rate of suspended solids at about 75 to 80 percent, but not nearly as good as using a biological process." The upgrade- the new secondary treatment facility- is a conventional activated sludge processor with a built- in selector process for nitrogen removal. There are aeration basins, secondary sedimentation tanks, waste- activated sludge and return activated sludge pump stations; a blower building with three blowers; an operations and maintenance building that will house the plant control center for the new plant; two dissolved air flotation thickeners; and an additional unstabilized sludge storage tank. " The design for this plant was actually ready to go 12 years earlier," says Smullen, " when the construction of the advanced primary plant was completed. We had to update it to current now constructing." The project is being constructed by the Tempe Arizona office of PCL Construction, Inc, who won the award last November through a best value procurement process. Smullen is the field office manager at San Diego, the most westerly of field offices in the US section of the IBWC. An engineer by trade, he works in operations; the field offices are for operations and maintenance. But this upgrade project is essentially a construction job, so he answers to both the division engineer of operations and maintenance and the division engineer of engineering services. The engineering department encompasses engineering, environmental management and, in this case, construction-" so I have a couple of bosses and I wear many hats," he says. The current South Bay facility is a physical chemical plant with no biological treatment. It uses ferric chloride and anionic polymer to precipitate as much of the suspended solids out

treatment plants throughout the Southwest. " This project exemplifies our expertise in the construction and upgrading of wastewater treatment facilities," says Luis Ventoza, vice president and district manager for PCL. " It is also important to add that we have a growing portfolio of successfully built water treatment facilities and pipelines." The upgrade project is slated to be complete by March 2011. In terms of how long the plant will continue to operate without another upgrade, it's designed to handle an ultimate buildout of 100 million gallons of wastewater flow per day, but any additional expansion beyond an average of 25 million gallons per day will be at Mexico's cost, according to the agreement made previously. " Mexico is building more secondary treatment plants," says Smullen, " and is working towards developing more reclaimed water sources with eventual indirect reuse of that water." standards, and we had to double the peaking factor with the addition of more tankage. The plant will be able to treat an average daily flow of 25 million gallons per day with a peak flow of 50 million gallons a day. In addition we are enhancing and expanding an existing SCADA system, for remote monitoring and control." Construction will also encompass civil site work including landscaping and irrigation, fire protection, plumbing, heating, ventilation, air conditioning, structural, mechanical, electrical and instrumentation controls. Because of the numerous processes and facilities required to handle these operations, treatment plants are among the most challenging structures to build. PCL Construction was chosen because of its expertise, with billions of dollars worth of projects annually, including the construction of water and sewer pipelines and PCL Construction / International Boundary and Water Commission August 09 www. bus- ex. com 167