This article was published on: 11/22/10 12:00 AM

Bend mulls purification options for city’s water

By Nick Grube / The Bulletin
Published: November 12. 2010 4:00AM PST

City of Bend water customers should soon get a glimpse of how much their monthly bills will increase over the next several years as a result of a planned $73 million upgrade to the Bridge Creek water system.

That increase is on somewhat of a sliding scale right now — between 37.5 and 45.5 percent over the next five years — because city councilors still need to make a number of choices on construction options that will impact the overall cost of the project.

The average residential water customer pays about $66.95 a month in the summer.

Councilors, who voted to move ahead with the $73 million over- haul, are expected to discuss their upcoming options for the project on Wednesday. In particular, they will focus on a water treatment option for the Bridge Creek system that is needed to meet federal clean water mandates.

Bend currently gets about half of its annual water supply from Bridge Creek, which is a tributary of Tumalo Creek. The rest of the city’s supply comes from wells that pump groundwater.

The city is upgrading and expanding its Bridge Creek system to meet the future demands of a growing population and also to replace aging pipelines that officials say could fail at any time.

Bend must also add a treatment system to comply with U.S. Environmental Protection Agency rules that require municipalities to treat for Cryptosporidium and other microorganisms that can lead to human illness.

The city currently has two treatment options to choose from. One uses ultraviolet lights to basically change the DNA structure of microorganisms so they can’t reproduce and therefore make people sick. The other is to use membrane filtration, which basically acts like a super-efficient colander to strain Cryptosporidium and other debris from the water.

Ultraviolet lights would be a cheaper option for the city, costing around $24.9 million as compared to nearly $30 million for the membrane filtration.

But city officials have been pushing hard for councilors to choose the membrane filtration option because it can filter debris from possible wildfires in the watershed, something a UV system cannot do.

Even if councilors choose to go with the UV treatment method, the city would build what would basically amount to a hole in the ground that would be in place so a membrane filtration system could be added should a wildfire occur.

Councilors will also have to make a decision on whether to add a $13 million hydropower plant to the water system in an attempt to generate green energy. They can also wait to include that component until later when more funds are available, or abandon the possibility altogether.

For many, this hydropower plant has been a major selling point for the project because it could possibly generate revenue to offset future rate increases. If councilors waited on this hydropower option, the estimated cost of the water system overhaul would be between about $55 million and $60 million reduced from the $73 million.

There is a nearly $30 million cost included in the overall project price tag no matter which treatment option councilors choose or if they decide to include a hydropower plant. That $30 million would be to replace about 10 miles of aging pipeline that runs from the Bridge Creek water intake facility near Tumalo Falls north of Bend down to another facility before being dispersed throughout the city.

City councilors are expected to make their decisions on the various components of the Bridge Creek project next month.

Nick Grube can be reached at 541-633-2160 or at ngrube@bendbulletin.com.