Let’s learn more about our wells

Published 1:30 am Tuesday, June 2, 2026

Vashon’s water supply, as many may know, derives entirely from rainfall, mostly harvested from wells drilled into the underground aquifers it percolates down into. To ensure the health of this resource long into the future, monitoring our withdrawals and any related changes in abundance is critical.

The island’s seven large water purveyors — District 19 and Heights, for example — keep track of both the quantity and quality of the water they extract from streams and wells, along with any changes in source water levels. These “Group A” providers serve most island users, but there are over 1,000 private wells here about whose performance and health very little is known.

The Vashon-Maury Island Groundwater Protection Committee has, since 2001, pursued what its name implies: working to make sure that the supply of water we depend on continues long into the future. Currently, two initiatives are underway to further this aim, designed to assist and involve private well owners on Vashon:A free, open public meeting with local well experts explaining how a private well works and how to keep it performing smoothly, and answering any questions attendees may have about their own system’s performance and other issues they’re concerned about. The meeting is upcoming on June 17, and will take place at the Land Trust Building on Bank Road from 6 to 7:30 p.m.

An outreach program to enlist private well owners to volunteer for periodic monitoring of their well’s water depth, which can help provide a broad view of any changes in water levels around the island. So far, 20 islanders have signed up; staff from King County’s Groundwater Program visit these Vashon properties once a quarter to take measurements. Less frequent pump tests, which measure the flow a well can provide, how much its water level lowers when used, and how long it takes to refill to its usual depth, are being considered for the future.

Ongoing water depth measurements let the participants know how their wells are doing, but a comprehensive, islandwide picture of well performance cannot be easily obtained from the relatively small number of monitoring sites we are currently attending to. An additional challenge is that although we speak of “the aquifer” that’s available here, there is no one large body of underground water at a predictable depth into which numerous wells can be drilled — a well in a particular site may be a reliable producer, while another drilled only a short distance away comes up dry.

This is because, in the island’s scrambled geology, the water-bearing layers of sand and gravel can be separated by other less porous materials and vary according to both distance and depth, leaving a scattered complex of smaller aquifers.

To sort out this geologic puzzle, it makes sense that the more wells we’re able to measure, the better understanding we’ll gain of how stable the overall supply appears over time, as well as where useful water is located. Toward this goal, the Groundwater Protection Committee would like to expand this community-driven source of well health, and is currently reaching out to the public for sign-ups. Potential volunteers may ask for details via rabard@comcast.net or (206) 463-3439.

Richard Bard is a member of the Vashon-Maury Island Groundwater Protection Committee.