Major upgrades now complete

A $95 million upgrade and expansion project at the city’s Central Treatment Plant brings it up to standards set by the state government and will help protect water quality in Puget Sound.

A major feature is a peak wet weather effluent pump station. It contains five, 900-horsepower Floway pumps. This station can be activated during extreme wet weather events. It greatly increases the plant’s treatment capacity. Previously it could treat 75 million gallons per day. The new station was called into action during heavy rains in January, when it treated about 130 million gallons per day, compared with the average dry season flow of 18 million gallons per day.

In the past, heavy rain would sometimes overload the plant’s capabilities and cause sanitary sewer overflows and the occasional need to discharge partially treated wastewater into Commencement Bay. The plant expansion minimizes the size and frequency of such occurrences.

Eric Johnson, assistant manager of the Science and Engineering Division of the city’s Public Works Department, was project manager for the upgrade. He said a primary reason for the project was to comply with the requirements for a discharge permit from the state Department of Ecology, which prohibits sanitary sewage overflow into Commencement Bay. “That was the primary driver for the upgrade.”

Johnson noted this does not mean the facility will never discharge overflow into the bay, but it does mean this is only likely to happen during extremely heavy storms.

A second reason is the age of the facility. It was built in 1952, and underwent some upgrades in the 1970s and 1980s. The need to meet the permit requirements allowed the city to replace some outdated equipment, according to Johnson.

A majority of funding, about $70 million, came in the form of low-interest loans from a revolving fund managed by Ecology. Ratepayers will pay much of the remaining cost.

Some of the new equipment began operating within the past two years. Much of the work was completed in the past five months, with the last of it finished last month.

The facility has new influent bar screens, a new influent pumping station and aerated grit facility.

Other improvements include replacement of the plant-wide disinfections system, landscaping and new computer controls. A new visitor center was also built.

“This involved a lot of work by a lot of people,” Johnson remarked.

All the work had to be done while the plant continued to operate. “It made for a very unique challenge.”

An open house was held on Oct. 7. Johnson said allowing the public to see the improvements is important as this is one of the largest projects the city has undertaken. Because of the nature of the plant’s function and its location on the Tideflats along Puyallup River, it is not as visible as high-profile facilities like the new convention center.

“To see this come to fruition is very rewarding,” Johnson remarked. “The staff should be very proud.”

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