Vashon’s drinking water comes from the rain and snow that falls on our saltwater-bound island. 30% of that precipitation percolates down through the soil to refill the island’s aquifer, an underground reservoir of sand and gravel that is our sole source of fresh water.
Whether you get your water from one of the island’s large suppliers, from a smaller neighborhood system or from your own private well, every drop comes from the same watering hole. There are systems in place to protect our water supply. The Washington State Department of Health (WA DOH) monitors water purveyors large and small. But oversight gets confusing for smaller systems and there are gaps in the safety net.
For example, owners of private residential wells are not required to test their water after an initial assessment from King County has found it potable. There are about 1,000 private wells on the island. If you have one of them, here are three things you can do to safeguard your own well and our collective water supply.
Isolate your well
As direct pipelines into the aquifer, wells can also be express routes for pollutants. Pesticides, fertilizers, gasoline, paint, waste from pets, livestock and humans — you name it. If it’s on the ground near your well it can wind up in your drinking water. To avoid contamination:
- Elevate your wellhead so surface water and runoff can’t pool or flood nearby;
- Create a 100-foot sanitary zone around your wellhead and don’t use, store or dispose of anything in that control area that you wouldn’t want coming out of your kitchen tap;
- Cap your well with a tight-fitting cover so nothing gets inside. Check the sanitary seal and the well casing regularly for any signs of wear and tear;
- Visit Washington State University’s Simple Tips for Well Maintenance online.
Test your water
The three most common well contaminants are coliform bacteria, nitrates and arsenic.
1. Coliform bacteria are unlikely to make you sick, but their presence is a sign that pathogens may be in your drinking water. The likely sources of contamination are at your wellhead or in your plumbing system. Public Health-Seattle & King County (PHSKC) recommends testing well water annually for small public systems. Since there’s no acceptable level of coliform bacteria, test results come back either Present or Absent. To learn what PHSKC advises if your well tests Present, visit this link.
2. Nitrates abound in fertilizers and in human and animal waste. They arrive in wells via surface runoff or underground seepage from nearby septic systems, barnyards or farmland. Nitrate levels above 10 parts per million (ppm) present a serious health risk for infants under six months. PHSKC calls for testing your well every three years — more frequently if nitrate levels exceed five ppm, or if they have jumped since your last testing period.
3. Arsenic occurs naturally in local rocks and soil and also as a result of historic industrial activity in nearby Tacoma. Health effects of ingesting arsenic vary depending on the person, dose and length of exposure. Long-term exposure (more than six months) to smaller levels of arsenic can raise the risk of heart disease, diabetes, nerve damage and many types of cancer (for more on that, see the state department of health website). Washington’s DOH recommends testing twice a year, in summer and winter, and warns that arsenic levels in water used for drinking or preparing food should not exceed 10 parts per billion. For more information, visit this link.
Track your water use and level
Because we all rely on the same water supply, conservation is critical. Install a source meter to track your household consumption. Measure and record the standing water level in your well twice a year (April and October). Consider sharing this data with the Vashon-Maury Island Groundwater Protection Committee.
The Committee is looking for private well owners who can help us get a clearer picture of water use on the Island and its impact on our sole source aquifer. Volunteer opportunities include monitoring your household use and the water levels in your well. If you’d like to participate or learn more, contact Greg Rabourn at 206-477-4805 or Greg.Rabourn@kingcounty.gov. (Subject line: WELL MONITORING PROGRAM.) Better yet, attend our next (virtual) Groundwater Committee meeting from 6:30 to 9 p.m. Wednesday, Oct. 28.
Mary Bruno is the chair of the Vashon-Maury Island Groundwater Protection Committee.