Tacoma Water officials have refined the cost estimates for new drinking water treatment equipment, and they’re about $10 million to $20 million higher than rough initial numbers.

And the cost-estimation models are based on a very early level of design, because a recommendation on which equipment to use is at least a month away.

The utility must comply with a federal rule, which takes effect in 2014, mandating that drinking water not contain the parasite cryptosporidium, which causes diarrhea. It also is anticipating issues about the long-term safety of water from the Green River, the source of most of Tacoma’s water.

The utility must choose between filtration and UV light disinfection. UV is less expensive but treats only crypto; filtration is more expensive but might be required in the future.

Utility officials plan to make a formal water treatment recommendation to the Public Utility Board on Dec. 16. The board could decide in December, or it could wait until next year.

The decision brings a guaranteed rate increase to the 160,000 residential customers in Tacoma, University Place and other parts of Pierce County, as well as businesses and cities on the system.

Utility officials’ initial estimates were $140 million for filtration and $70 million for UV. Both estimates included constructing storage wells. Utility officials now have included an option without storage because that would cost the least, but they don’t advise it. Storage wells are needed to manage the risks of a UV treatment system, which include dealing with contaminated water if the UV lamps break.

At a meeting last week for the citizens’ stakeholder panel, updated cost estimates for two variations on both approaches were presented, with the caveat that they are based on only a 5 percent level of design. The estimates consider expenses for design, construction and startup, as well as operation and maintenance of the plant for 40 years. They were:

 • UV without storage wells: $47 million capital cost; $1.2 million annually for operation and maintenance

 • UV with storage: $80 million capital cost; $1.5 million annually for operation and maintenance.

 • “Hybrid” filtration – a setup designed for maximum use in the winter – with storage: $169 million capital cost; $4.1 million for operation and maintenance.

 • Conventional filtration with storage: $187 million capital cost; $5.1 million for operation and maintenance.

Utility officials believe a filtration system is a better investment because it not only treats crypto but also has other benefits, including removing the dirt and other debris currently in the water.

Officials said about a third of the construction costs will be paid by Tacoma Water’s regional partners: the Regional Water Supply Partners, the City of Kent, the Covington Water District and the Lakehaven Utility District.

Those partners also will cover about a quarter of the operating expenses. But Tacoma Water ratepayers will foot the bulk of the bill in the form of rate increases starting in 2011. Increases are estimated at between 6 percent and 20 percent, depending on which treatment option is chosen.

Utilities spokeswoman Sonja Hall told the stakeholders group the utility has received some feedback and welcomes more.

“The majority of folks outside our largest customer were in favor of filtration,” she said.

That customer, Simpson Tacoma Kraft, makes industrial-use paper on the Tideflats and is the largest user of Tacoma water.

To control expenses, Simpson is considering sources beyond Tacoma Water, said Dave McEntee, vice president of operational services and external affairs.

“We’re looking at all our alternatives,” McEntee said, “what’s the city required to do, what’s the cost-benefit required to do something above and beyond what’s required, what are our conservation opportunities in the mill, are there other water substitutions out there.”

Kathleen Cooper: 253-597-8546

kathleen.cooper@thenewstribune.com

WHAT’S NEXT

Today: Public Utility Board

 • Study session: 3 p.m., Public Utilities Building Ground Floor Conference Room, 3628 S. 35th St., Tacoma

 • Public meeting: 6:30 p.m. Public Utilities Building Auditorium, 3628 S. 35th St.

Thursday: Tacoma City Council’s Environment and Public Works Committee

4:30 p.m., Tacoma Municipal Building, 747 Market St., Conference Room 248

More Information: www.tacomawater.com/decision