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 to cool the steam back into water. This re-condensed water is cleaned and reused again and again in a closed loop and is not released to the environment.
Cooling water from the Columbia River carries the residual heat from the condenser to six mechanical draft cooling towers, where it is dissipated into the atmosphere as clean water vapor which is sometimes visible from many miles away.
Cooling water system chemistry is controlled to minimize algae growth, scaling, and 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. Each of these chemical controls help the station use water efficiently.
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 intake structure is approximately 20 feet long and placed parallel to river flow approximately 350 feet offshore at the seasonally low water level.
Water flows by gravity to the River Pumphouse. The intake structures for Columbia Generating Station were constructed in the late 1970s, and were specifically designed to minimize Columbia Generating Station’s impact on salmonid fry when taking make-up water from the Columbia River.
How do we know there is little impact? Two studies were conducted, both before and after Columbia Generating Station started operating.
In the 1985 study, the monitoring program looked at both impingement (what happens when water pressure pushes a fish against an intake) and entrainment (what could happen when small fish is pulled through the intake screens but can’t get out) between April and September. No juvenile salmonids were found to be affected. This monitoring program was undertaken with a study plan review by the National Marine Fisheries Service.
A second study was undertaken in 2018 to 2019 to update the entrainment data from the 1985 study. The final report found a very low impact on fish from the Columbia Generating Station.
The cooling 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 needs about 20 million gallons of water from the Columbia River each day for cooling. Of that volume, almost 1.9 million gallons a day of clean water, are returned to the river. For reference, about 35 – 40 million gallons of water pass by the station’s intake structure every minute.
What’s in the Water We Return to the River?
Energy Northwest prepares a monthly Discharge Monitoring Report for the Energy Facility Site Evaluation Council that certifies all the water returned to the river meets the requirements of the station’s National Pollutant Discharge Elimination System (NPDES) permit. The NPDES permit requires pH levels to be within specified limits and disinfecting agents like chlorine must be less than or equal to 0.1 mg/L. A milligram is equivalent to 1 part per million. Energy Northwest also monitors chromium and zinc as a condition of the permit, which have permit limits of 8.2ug/L and 53ug/L respectively. A microgram (ug) is equivalent to 1 part per billion.
The station’s NPDES permit does not allow polychlorinated biphenyls (PCB’s) or any of the EPA’s 126 priority pollutants to be above detection levels.
Energy Northwest remains in full compliance with all environmental regulations related to our cooling water discharge.
Columbia Generating Station's NPDES Permit Columbia's NPDES Permit Fact Sheet (PDF)