Spokane County sewage plant coming along

Nearly 5,000 cubic yards of concrete and 15,500 feet of underground pipe have gone into Spokane County’s single-largest construction project, which is a quarter complete.

The $167 million sewage treatment plant at 1004 N. Freya St. will serve most of the Spokane Valley and could go online in 17 months.

The new plant is about 28 percent complete in terms of construction, 37 percent in terms of budget. Officials say the project is on schedule for startup tests in September 2011. If no problems are found and necessary permits are obtained, the plant could begin processing sewage in January 2012.

The construction is within budget, according to the project director, county water reclamation manager Dave Moss.

Thanks in part to a mild winter, two buildings have been completed except for interior finishing.

One is the treatment operations facility, where 10 or so contract-provided operators and a county manager – likely Moss – will have their offices and a laboratory for tests.

The other building will house the water resources center, which will provide public education as well as meeting space. Exhibits may include explanations of the treatment plant, and a model of the Spokane Valley/Rathdrum Prairie Aquifer and the Spokane River.

Moss also envisions an interactive display in which visitors can follow a drop of water through the treatment process. Or maybe a display linked to the plant’s actual control panel, so visitors can see what operators are doing.

However, Moss said visitors and neighbors won’t smell what the operators are doing. All the processes will be covered, and air in each structure will be filtered, he said.

“We will not be a smelly neighbor,” Moss said.

In addition to early completion of the office and training buildings, the mild winter allowed almost half of the planned 9,600 cubic yards of structural concrete to be poured. Also, 15,500 feet out of 40,200 feet of underground pipe were laid.

Seven major structures are to be added this summer.

The construction is being done by local subcontractors working for Denver-based CH2M HILL, an international engineering firm hired to design, build and operate the plant.

The county sold about $126 million in bonds in 2009 for the treatment plant and other projects, and will use a $64.9 million low-interest state loan to finish paying for the wastewater work. User fees will repay the money.

The financial plan assumes the state Department of Ecology will issue a permit to discharge treated effluent into the Spokane River by the time the plant is finished.

The U.S. Environmental Protection Agency recently gave final approval to a river cleanup plan that would allow a permit. However, the plan for reducing oxygen-robbing contaminants from the river imposes a heavy burden on existing dischargers and Long Lake Dam operator Avista Corp.

If Avista or any of eight private and public dischargers or their critics files a lawsuit to block the plan, a judge could delay implementation until the dispute is resolved.

County officials hope a yet-undeveloped program for trading phosphorus-removal credits – which the EPA supports – can be developed in time to prevent litigation.

If there is a lengthy delay, lack of treatment capacity in the Spokane Valley could force the county to develop a $42 million wetland project at Saltese Flats to dispose of treated effluent.

A future project could reduce the need for river disposal by piping treated wastewater to the county fairgrounds and other customers looking for inexpensive water for irrigation or industrial uses. The pipe eventually could be extended to Saltese Flats.

County utilities director Bruce Rawls is confident the treatment plant will meet the new river-discharge standards.

The regulations target phosphorus and ammonia as well as organic materials that remove oxygen from rivers and reservoirs when they decay. Phosphorus and ammonia feed algae and other plants that have the same effect when they die.

Rawls said phosphorus has the largest effect on water quality, and phosphorus removal is the new treatment plant’s strong suit. Also, the county gets phosphorus-removal credits for converting Spokane Valley from septic tanks to sewers.

Moss said “world-class filtering” will remove 99.9 percent or more of phosphorus after extensive processing to remove other contaminants and bring the phosphorus to a semisolid state.

The key is a screen of 6 million porous, strawlike fibers. Each tubular fiber is about 2 1/2 yards long and has an outer diameter of less than eight-hundredths of an inch.

Sheets of the fibrous tubes are dipped in what Moss describes as “soup,” and a pump creates suction on one end of the tubes as though they were straws. But the other end is sealed, so the liquid is drawn in through microscopic holes in the sides of the tubes.

Each hole is just four-hundredths of a micron in diameter, “much, much smaller than a human hair,” Moss said. Water enters the tubes, but phosphorus is trapped on the outer walls.

“There’s almost none of it left in the water,” Moss said.

Another of the plant’s whiz-bang features is a system for using methane gas.

Burning the gas will generate enough electricity to operate part of the plant. The methane also will help heat buildings as well as the tank that extracts the gas in the first place.

The county’s 8-million-gallon-a-day treatment plant is small in comparison with the city of Spokane’s 44-million-gallon plant, which is expected to be expanded and upgraded in a few years.

However, the county will continue to use 10 million gallons of capacity at the city plant, for which it has a long-term contract.

Even with the planned upgrades, the city facility will offer “very cost-effective treatment, compared to a new plant,” Rawls said.

He said at least 2 million gallons a day of county sewage from suburbs north of Spokane will always go to the city plant.

Also, when flow from the Spokane Valley exceeds 8 million gallons, which is expected in 2013 or 2014, some of that area’s sewage will again go to the city plant.

Plans call for the county plant to expand to 12 million gallons a day when the Spokane Valley flow reaches 18 million gallons – expected in about 20 years.

The plant’s design and 20-acre site allow for a maximum capacity of 24 million gallons a day.

“Ultimately, we think we can handle whatever will come from our customer base in the Valley,” Moss said.