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Section D: PrnrrT Or$xnTtorrs Page I? <br />that the launders in the secondary clarifiers had <br />notbeenproperlyanchoredwheninstalled. When <br />the clarifiers filled with river water, the buoyant <br />force caused several launders to break loose. <br />Phase two was conducted through February and <br />March of 1984. Equipment was further tested by <br />continuously recycling the river water remaining <br />in the many basins and clarifiers through the plant. <br />Extensive testing also was performed on the return <br />activated sludge pumps and chlorine feed equip- <br />ment. No major problems surfaced to delay the <br />scheduled start-up date. <br />TRANSITION <br />The East Bank Interceptor (EBI), built to convey <br />all the Springfield sewage to the new facility, was <br />^ TREATMENT PROCESS UNITS <br />Each treatment process unit of the regional treat- <br />ment plant serves a unique purpose, contributing <br />to removal of wastewater pollutants and to the <br />production of a stabilized sludge. The main unit <br />processes arepretreatment, primary treatment, sec- <br />ondarytreatment, final treatment, sludge thicken- <br />ing, and sludge handling. <br />The unit processes that contribute the most in <br />achieving optimum reduction of biological oxygen <br />demand (BOD) and total suspended solids (TSS) <br />put into partial operation in January 1984. Until <br />late March, half the Springfield wastewater was <br />conveyed through the EBI into the old Eugene <br />plant and half continued to be treated at the <br />Springfield plant. Immediately before start-up of <br />the new plant, the entire Springfield sewage flow <br />was routed through the EBI to the old Eugene <br />plant, and the Springfield plant was closed down. <br />All its basins and piping systems were flushed and <br />filled with clean water. <br />On Apri12,1984, the new regional plant came on- <br />line. Over the next six months, the operation of <br />the old Eugene plant was gradually phased out. On <br />June 29,1984, the new facility began treating all of <br />the Eugene/Springfield area's wastewater. The old <br />Eugene plant was eventually shut down, and both <br />old plants were demolished in 1989. <br />are primary and secondary treatment. Anaerobic <br />digestion is the method used to reduce volatile <br />solids and pathogens in the sludge produced by the <br />plant. <br />PRETREATMENT <br />The pretreatment complex is the first process unit <br />of the treatment plant. The main process compo- <br />nentsare two raw wastewater receiving points, raw <br />wastewaterpumping, comminution, flow measure- <br />