WALLA WALLA — The city’s primary source of water will be shut off for two days.
But not to worry, as city officials plan to rely completely on well water on Tuesday and Wednesday.
Mill Creek generally makes up 80-90 percent of the city’s water, except at times of the year when there isn’t enough water in the creek or there is too much and the water is turbid.
“This occurs during late fall to early spring due to heavy rain or snow melt. In summer when stream levels start declining we also use a higher percentage of ground water,” said Mori Struve, public works manager.
“The maximum use of ground water could be up to 100 percent, which will be the case when we do the intake dam area cleaning July 30 and 31.”
The area to be worked on is about 30 miles up the creek at the base of a 36 square-mile watershed, where crews will clean out silt, rocks and vegetation that have accumulated near the inlet pipe.
During the two days, customers may notice their water will taste or smell different.
According to the United States Geological Survey department, the basalt aquifers in the region were formed from lava flows and melted glaciers thousands of years ago.
Several years ago, the city’s water treatment department had carbon 14 dating performed on water samples from the aquifer and determined the ground water to be 20,000-years-old, but still safe to drink.
The city uses seven wells to collect water from the aquifer, and when it has excess water it recharges the aquifer with water form Mill Creek.
City officials are asking residents to eliminate unnecessary water uses during the two days, like irrigation or washing the car.
For more questions, contact the city’s Water Division at 527-4380.