Groundwater to be added to Portland supply system

The Portland Water Bureau will begin adding a small portion of water from its Columbia South Shore Well Field into the water distribution system on Tuesday, July 30.

The blending part of a maintenance operation. It is scheduled to end on Aug. 9.

The operation does not mean water behind the dams in the Bull Run watershed have fallen so low that the groundwater must be added to solve turbidity problems.

According to the bureau, the groundwater supply is a complex system composed of electric pumps, chemical feed systems, electronic controls and other equipment that must be operated regularly to identify maintenance needs. By doing so routinely, the bureau helps ensure the reliability of the system when needed, either in an emergency or to meet seasonal supply demands.

The rate of groundwater pumping will vary throughout each day. Groundwater will be pumped at a rate of approximately 18 million gallons per day during work hours. No pumping will occur at night. The rate of groundwater production may decrease toward the end of the operation. It may be extended as necessary.

The average contribution of groundwater to the system will be approximately three percent or less of the total daily water demand, the bureau says. Because of this, the bureau does not expect there to be a large change in water quality. It takes approximately 24 to 60 hours for the blended water to make its way through the distribution system to homes and businesses, depending on location and water demand.