Most citizens unaware of the intricate process

When people in Corvallis turn on their tap, they expect a safe and reliable water supply. What they don't know is what it takes for the city to ensure that safety and reliability.

Most people have some understanding about the city's process to treat and filter water to ensure bacteria and contaminants have been removed. But this is only the first step in protecting the water supply. Once the water has been treated to a level that it meets or exceeds all state and federal regulations, it is put into the distribution system of pipelines, pump stations, and reservoirs, where it is available for use by customers.

While in the distribution system, the city continues to monitor the water quality. This continued monitoring is important because the water may remain in the system for several days before it is used. Real-time, on-line monitoring points in the system measure such things as water pressure, pH (acidity), chlorine residual (shows the remaining chlorine in the water for disinfection), and conductivity (an indicator of possible contamination).

If the readings on any of these vary beyond normal limits, the system automatically sounds an alarm resulting in an immediate response from city staff.

The water in pipelines and reservoirs is routinely sampled and monitored for chlorine residual and water age to make sure the water is fresh and free from harmful bacteria. The water levels in the reservoirs are also managed to minimize storage time, but still provide sufficient capacity for emergencies.

Another water quality program is the periodic flushing of the water mains. Water at a high pressure is flushed through the mains to remove rust and sediment from the pipes. The entire city is typically flushed on a four-year schedule. Water mains that dead-end (don't loop back to the rest of the piping system) are flushed more frequently, about once a year, to maintain adequate water quality. Dead-end lines are typically found at the end of cul-de-sacs.

The city also protects against contaminants flowing back into the water system. Devices to prevent backflow are required in specific circumstances where the threat is highest, such as industrial facilities. The device protects the water supply from any dirt, bacteria or chemicals that could back-flow to the water system. On residential properties, a backflow prevention device is required for irrigation systems. The city operates a state-mandated program to ensure appropriate backflow prevention devices are installed and tested annually.

In other ways, the city ensures the drinking water is delivered in the most efficient and cost-effective manner possible. One of these is detecting leaks in the city infrastructure to prevent unnecessary water loss. Every year a contractor is hired to check the water system for leaks.

About 80 miles of pipe or one third of the water system is surveyed annually. Leaks that are found are promptly repaired. One found this year was leaking at a rate that would amount to more than 13 million gallons of water per year if it was not fixed. The leak was not reaching the surface, and could only be detected through the use of specialized leak detection equipment.

Another way the city is enhancing cost-effectiveness is with water meters. Radio-read water meters are being installed that enable the meters to be read without sending a staff person to inspect each water meter. The radios on the meters send a signal to a receiver in a city vehicle and consumption information is automatically recorded. Radio meter reading provides more accurate billing at a lower cost to the customer.

If you have questions about the water system, call the public works department at 766-6916.

Mary Steckel is the administrative division manager with Corvallis Public Works.