Salinity Intrusion in West Marin System Source Wells
(Posted August 20, 2020) Unprecedented salinity intrusion has occurred in two wells which North Marin Water District uses as sources of drinking water in the West Marin system.
These two wells, located near the former Coast Guard housing property in Point Reyes Station, have experienced periodic and seasonal salinity intrusion for many years. In 2015, NMWD completed permitting and construction of a well and pipeline that brings water from a different source, out of the reach of tides. This third well is situated approximately a mile and a half east of Point Reyes station adjacent to the Gallagher ranch.
Unfortunately, the third well is unable to produce enough water to meet 100% of the volume demands of our customers in the summer months and the salinity intrusion at the Coast Guard wells has continued to worsen, likely due in part to sea level rise.
This year, under dry-year water conditions, we have seen the salt levels in the water produced from the Coast Guard wells rise to unprecedented levels. While there is no direct health concern from the salt for most people at this concentration, it does affect the taste. Customers that may be on sodium restricted diets should consult their physicians to see if the additional sodium is a concern for them.
Additionally, bromide, a component of the salt water that has increased, can also contribute to the formation of disinfection byproducts. We have taken every action available to keep disinfection byproducts as low as possible and continue to monitor their concentrations. If they rise to an unsafe level we will, in consultation with the California Division of Drinking Water, communicate this to our customers.
In order correct the situation, North Marin Water District is actively working to construct additional sources of water that are not prone to salinity intrusion. The acquisition of land, planning and permitting have been going on for two years. We hope to have this new source constructed and available for water supply in 2021.
Emergency water conservation measures remain in place and reduced water use decreases our dependence on wells impacted by the salinity intrusion.
More information about water quality can be found at https://nmwd.com/your-water/water-quality/
If you have questions or concerns that are not addressed here, please call Pablo Ramudo, Water Quality Supervisor at 415-761-8924.