New waste water plant taking shape
September 13, 2012
The sounds of concrete pumper trucks, cranes, excavators and trucks hangs in the air about SR 4 at Cathlamet.
Pacific Crest Construction and its subcontractors are hard at work building a new waste water treatment plant for the town of Cathlamet.
The $8 million plant will replace Cathlamet's sewer lagoon sewage treatment. The project is scheduled to be complted around the end of 2014. Sewage will flow down to pump stations near the present plant and be pumped uphill to the new plant. There the wastewater will work its way through an oxidation ditch and clarifiers to remove solids, treat bacteria and clean the water, which will flow down another pipeline and into the Columbia through the present site's outfall.
Last Friday, the contractors were pouring the walls of one of two secondary clarifiers. Contractors expected to pour the walls for the second clarifier this week.
The operations building lies between; pouring its walls was expected later this month.
On the lower level of the two storey building will be the pumps for the clarifiers. On the upper level will be the control center, a small office, sample testing lab, and the electrical control room for the plant
The construction schedule calls for having the structures in place by the end of this year. Next year, they'll begin installing piping, electrical systems and other internal operating gear.
The contractor has poured the base of the oxidation ditch. They haven't started on the headworks, which will be located on a terrace above the oxidation ditch.
"It's all gravity flow," commented Larry Hartwick, resident inspector for Gray & Osborne. "The sewage will come into the headworks, go down through the oxidation ditch, then the clarifiers and then the treated water will go out to the river."
The contractor has piled mounds of dirt up on the hill. Much of the material will be pushed into place around the oxidation ditch, control center and secondary clarifiers, bringing the surface level close to the tops of the secondary clarifiers and the top floor of the operations center.
Rainfall and groundwater could present challenges to the project.
"One of our challenges is to have a dewatering plan," Hartwick said. "The contractor will cover the stockpiles of dirt with visquine to protect them."
The contractor encountered a couple of springs when clearing the site.
"We expected to find some," Hartwick said. "We addressed them with minor changes to the drainage system. We were prepared for them; we just didn't know where they were."