Message from Metropolitan Water District of Southern California
Notice: Regarding Taste and Odor Production and Treatment in Lake Skinner

Metropolitan Water District of Southern California reported a recent sampling indicates that concentrations of the taste and odor compound methylisoborneol (MIB) are increasing in Lake Skinner. The MIB concentrations in the lake were up to 36 ng/L on September 9, 2024. To control the naturally-occurring cyanobacteria responsible for MIB production, Metropolitan has scheduled a copper sulfate treatment for Lake Skinner on Wednesday, September 18, 2024.  

Rainbow Water receives water from the Robert A. Skinner Treatment Plant in Temecula. It is important to note that MIB poses no health risks and that your water supplies remain safe. Most consumers can detect MIB in their drinking water at levels above 10 ng/L; however, some consumers can taste or smell MIB at 5 ng/L or less. Consumers who detect MIB in their treated water supplies may describe it as a musty odor.

San Diego raw water pipelines No. 3 and No. 5, and the Skinner Plant will be transitioned from 0% to 50% lake bypass on Monday, September 16, 2024, and will be transitioned to 100% lake bypass for a short period during lake treatment, starting on Tuesday, September 17, 2024. The bypass may be adjusted as needed to accommodate water quality and operational needs. Throughout this period, the raw water pipelines and the Skinner Plant will continue to maintain a State Water Project blend of approximately 25%.

The Skinner Plant is currently using ozone and hydrogen peroxide to enhance MIB removal. 

Key Points for Customers

• The taste and odor changes do not create any health risks; all water being delivered meets state and federal safety standards.
• Algae growth is a common challenge at lakes around the world when air and water temperatures are elevated for long periods, typically the late summer and early fall.
  • High temperatures this summer have created additional opportunities for algae growth.
• Certain freshwater algae produce organic compounds (such as geosmin and methylisoborneol) that give water an earthy or musty smell.
• Refrigerating drinking water can help reduce aesthetic issues.

Additional updates will be provided as new information becomes available.

If you have inquiries, please notify Metropolitan’s Water Quality Line at 1.800.354.4420 to report the issue.