Fire could threaten Washington County water supply
The fire burning out of control approximately two miles from Hagg Lake poses a potential threat to Washington County's primary water supply, both now and after it is extinguished.
An team consisting of representatives from the various agencies in the county that use the water are monitoring the situation closely and drawing up plans, according to Tacy Steele, spokeswoman for the Hillsboro Water Department.
"It is not an emergency at this time, but we will be prepared to act, if necessary," says Steele.
According to Steele, the Joint Water Commission Water Treatment Plant that purifies the water from the lake should be able to handle most potential problems.
The biggest threat now is turbidity in the water caused by falling ash and embers. Steele says no ash has been detected in the water so far, but the fire is expected to continue burning.
A similar threat is likely to occur when rains start to fall in coming weeks and months. The fire is burning in the watershed that feeds Scoggins Creek, the primary source of water for Hagg Lake. Rains are likely to wash debris from the fire into the creek and lake, Steele says.
According to Steele, filters at the treatment plant should be able to remove all the sediment from the lake water. That happened in 1996 when heavy rains causes flooding that created turbidity in the lake.
"The filters normally have to be cleaned every 70 hours. In 1996, they were being cleaned every six to eight hours. it slowed the treatment process, but it worked," says Steele.
An unknown problems is what happens if chemical retardants are used to fight the fire. Water from the lake is currently being scooped up and dumped on it by helicopters. Removing chemicals from the water would require a different process than filtration.
"That's something we would have to figure out," says Steele.
The water supply system in Washington County is complicated. The primary source is the Tuaaltin River, which is supplemented with water from Hagg Lake in the summer. Supplemental lake water is not needed in the winter, but the lake occasionally rises so high that it spills into the Tualatin anyway.
The treatment plant is operated by the Joint Water Commission Water, which is comprised of Tualatin Valley Water District and the cities of Hillsboro, Forest Grove, and Beaverton. It also wholesales water to North Plains.