Cooling Tower Recirculation Water

​​​​​​​​​Columbia Generating Station produces a tremendous amount of energy from water that is boiled to make steam. To make that happen, there are two separate closed-loop systems at work – reactor recirculation water and cooling tower recirculation water.

The steam generated from the reactor recirculation system is turned back into water after passing through our steam condenser: a giant heat exchanger that uses the cooling tower recirculation water system.

Cooling water from the Columbia River carries the heat from the condenser to six mechanical draft cooling towers where it is dissipated into the atmosphere as water vapor. This is known as a closed-loop or closed-cycle cooling system.

Circulating water system chemistry is controlled to minimize algae growth, scaling and general corrosion. Other chemical additives are used to increase the effectiveness of chlorination, to act as a silt dispersant, and to introduce corrosion inhibitors into the raw water.

Cooling Water Intake Structure

Columbia Generating Station gets its cooling water from the Columbia River through two 42-inch diameter intake structures perforated with 3/8 inch diameter holes, each approximately 20 feet long and placed parallel to river flow approximately 350 feet offshore at low water. 

Water flows by gravity to the River Pumphouse. The intake structures for Columbia were designed and constructed in the late 1970s. The intakes were designed to minimize the impact of make-up water from the Columbia River, with particular emphasis on salmonid fry.

How do we know this? Two studies that were conducted, both pre- and post-operational.

In the 1985 study, the monitoring program looked at both impingement and entrainment between April and September. No juvenile salmonids were found to be affected. This monitoring program was undertaken with study-plan review by the National Marine Fisheries Service.

A new study was undertaken in 2018-2019 to update the entrainment data from the 1985 study. The final report was submitted Feb. 26, 2020, and found very low impact on fish. 

The circulating water system consists of the circulating water basin, three circulating water pumps, six mechanical draft cooling towers, and the necessary valves, piping, controls and instrumentation to continuously transport heat from the main condenser to the atmosphere.​​

Water Quality in the Columbia

Columbia Generating Station uses about 24 million gallons of water from the Columbia River each day for cooling. About 1,700 gallons a minute, or 1.872 million gallons a day, are returned to the river. About 35-40 million gallons of water pass by our intake structure every minute.

What’s in the water we return to the river?

Energy Northwest prepares a monthly Discharge Monitoring Report for EFSEC that certifies all the water returned to the river was in accordance with the site National Pollution Discharge Elimination System (NPDES) permit. The permit requires pH levels to be within limits and halogens near undetectable, at less than or equal to 0.1 milligrams per liter. Energy Northwest also monitors copper, chromium and zinc as a condition of the permit. The acceptable levels for chromium are 8.2 micrograms per liter and 53 micrograms per liter for zinc, while copper does not have a limit. The existing permit set a zero standard for polychlorinated biphenyl and a non-detection standard for 126 priority pollutants. Note: chromium and zinc are already present in the Columbia River.

Energy Northwest remains in full compliance with all environmental regulations related to our circulating water discharge.​

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