Water Supply Emergency Curtailment Plan
Current City of Corvallis Water Curtailment Plan
This plan is designed to guide water management staff in the event of a water shortage.
System Capacity and Historical Water Shortages
The current maximum production capacity for the Corvallis water system is 24.5 million gallons per day (mgd) – approximately 3.5 mgd from the Rock Creek Water Treatment Plant and 21 mgd from the Taylor Water Treatment Plant. There are nine reservoirs in the distribution system that provide a total of 23 million gallons of treated water storage. Except in emergency situations, these reservoirs must be maintained at minimum levels to provide water for fire suppression.
Maximum daily demand has been as high as 13.4 mgd in July, 1999 and 13.8 mgd in June, 2000. Since 1987, the greatest daily demand recorded was 15.9 mgd. Treatment capacity is greater than historic demand. Should treatment capacity be reduced by some unforeseen circumstance, the production deficit can be supplied from water stored in the system's reservoirs for a limited time. Using stored water to meet maximum daily demands, however, puts the utility at risk for meeting crisis water demands (e.g., a significant fire requiring large quantities of water or a spill in the Willamette River which makes the water unusable for an extended period of time).
The potential for such a scenario prompted the City to develop a water curtailment plan. In 1994, the City Council adopted the city's first water curtailment plan. In July 1994, Stage 1of the curtailment plan was put into effect as daily water demands exceeded production capacity for four consecutive days. This is the only time the curtailment plan has been executed, and since then the treatment capacity from the Taylor plant has been increased from 14.5 mgd to 21 mgd.
Water Shortage Identification
Some situations may occur that create the potential for a supply shortage. These situations include but are not limited to:
- An extended period of dry, hot weather
- Water rights withdrawal limitations
- Contamination of source water supplies (Willamette River and/or Rock Creek)
- Interruption of commercial power supply to a critical part of the City water system (Taylor Water Treatment Plant or water pumping stations)
- Major water transmission line break
- Reservoir failure
- Other major catastrophic event.
If one or more of these scenarios creates the need for water curtailment, the actions taken will vary depending on the time of year and the expected duration of the situation. The following guidelines will be considered during a curtailment event:
- Maximize public health and safety
- Meet Safe Drinking Water Act standards
- Minimize disruption to the public
- Protect and enhance the public's trust in the City
- Be consistent in phasing in curtailment measures as water shortage continues
- Apply measures in a fair and equitable manner in the best interest of the public
- Maximize coordination of responses with other departments within the City
- Minimize impact on the environment
- Limit liability
In general, the response to a water shortage is development of strategies that create a reduction in daily demand for water. This water curtailment plan identifies four stages of water shortage. The first stage is an alert to the potential of a water shortage, and the fourth stage is a critical water shortage that threatens the ability of the City to deliver water to customers for life sustaining and safety needs.
Water Curtailment Measures
These curtailment measures consist of four severity stages, and they can affect the city as a whole or only specified service areas. At each stage, restrictions imposed at the previous level(s) remain in force. The plan provides flexibility and enforcement capability. At any stage, additional restrictions can be imposed if they are deemed necessary. In some extreme cases, some stages can be skipped (e.g., expectation of an extended water production capacity reduction). Should the plan have to be implemented, notification to the general public will be primarily through the local news media. Direct contact will be made with large customers and institutions as the need requires.
