West Linn's and Oregon City's water supply was compromised after heavy rain Dec. 29, causing West Linn to tap into its emergency intertie with Lake Oswego
The South Fork Water Board (SFWB), which is the water supply agency for both Oregon City and West Linn, was forced to shut down its drinking plant in Oregon City last Thursday afternoon when workers noticed the system was not functioning properly.
Plant officials suspect large debris, such as a tree, in the water damaged a fish screen, according to John Collins, SFWB general manager. The screens are part of the water intake structure and prevent fish and debris from being drawn into the pumping system.
Collins said the plant typically pumps 10 million gallons of water a day and was found to be pumping just seven million a day last week, showing a sign of restriction.
Plant workers fired up a smaller pump and conducted a visual inspection last Thursday evening, finding debris on the top of the wet well, indicating that a screen had been damaged.
A team of divers entered the intake facility's wet well Friday morning, but turbulent water made for dangerous diving conditions and a complete inspection was halted.
Waiting for water levels to recede, divers re-entered the wet well Wednesday morning and confirmed damage to the screens, said Collins, adding that the divers saw no structural damage.
'At this point in time, it is believed the damage is limited to the fish screens,' Collins said. 'By stopping the production of water, the SFWB is minimizing the risk of incurring damage to other parts of the intake system.'
The intake system was constructed in 1996, and this kind of failure has never occurred before, he said. However, West Linn has had to tap into the Lake Oswego in the past during water system repairs, according to Lake Oswego Water Treatment Plant Manager Kari Duncan.
'It's not the first time by any means we've had damage,' Collins said.
'Historically, West Linn relies on Lake Oswego's water every two or three years, usually for a few days at a time,' Duncan said. 'A number of years ago, Lake Oswego provided water for several weeks while West Linn crews performed major maintenance on their only water supply line.'
The water intertie agreement with Lake Oswego was made in 1984, and the pipeline and pumps are located near Lake Oswego's water treatment plant in West Linn's Robinwood neighborhood.
West Linn started receiving the emergency water Dec. 29 around 4 p.m. North Clackamas County Water Commission is also supplying emergency water to Oregon City.
With water demands low this time of year, there have been no problems for either city, which are receiving ample emergency water. West Linn is getting about 2.8 million gallons a day from Lake Oswego, according to Jane Heisler, Lake Oswego-Tigard Water Partnership's director of communications.
'The timing for is good - our demand is low this time of year. We're planning on an indefinite time period - days or even weeks,' Duncan said.
Collins estimated it would take two or three days to repair or replace the screens and another couple of days to clean debris. This work must be completed before water will be restored to Oregon City and West Linn. The SFWB is owned in equal shares by the Oregon City and West Linn and withdraws and treats water from the lower Clackamas River to produce water for domestic and industrial purposes for approximately 65,000 people.