Vashon-Maury Island is an island that lies in the Puget Lowland within the boundaries of King County. This island encompasses about thirty-seven square mile area of which 29.7 square miles is Vashon Island and 7.0 square miles is Maury Island. The two islands are linked by a narrow isthmus and are not therefore, two truly independent islands. The island is bordered on the west by Colvos Passage (across from the Kitsap Peninsula), on the south by Dalco Passage (from Tacoma), on the east by Puget Sound and King County, and on the north by Puget Sound.Vashon Island is about 13 miles long (north to south) and 4 miles across (east to west) in the widest areas. Maury Island is about 5 miles long (northeast to southwest) and about 1 mile across (northwest to southeast).

Vashon-Maury Island ground and surface waters provide all of the water needed for residential, commercial and agricultural needs. Water quality on Vashon-Maury Island is generally excellent. All drinking water sources on the island (springs, surface water, and groundwater) are supplied by local precipitation. Vashon-Maury Island was designated a Sole Source Aquifer by the United States Environmental Protection Agency in June 1994. The majority of the residents of Vashon-Maury Island get their drinking water from public water systems (PWS).

Vashon-Maury Island Groundwater Protection Committee

Groundwater Data

Vashon-Maury Island Groundwater Management Plan

Vashon-Maury Island Groundwater Maps

Vashon-Maury Island Watershed Plan

Groundwater Studies

Vashon-Maury Island Groundwater Monitoring
Learn about monitoring to assessing the status of Vashon-Maury Island water resources

The Vashon-Maury Island Water Resources Evaluation project was completed in 2010. This work assessed the water resources of the island and provided a better understanding of how different activities can adversely affect the island's water quality and quantity that lead to an updated, more accurate water supply budget for the island.

Vashon-Maury Island Marine Recovery Area

The Marine Recovery Area is a specific designation that establishes a goal of protect, preserve and restore shellfish harvest opportunities by assuring that property owners within the Marine Recovery Area inspect, and repair or replace as necessary, their On-Site Sewage (OSS) system.

Quartermaster Harbor Nitrogen Management Study

This 4 year (2009-2012) study evaluated the role of nitrogen in the risk of lethal, low-level dissolved oxygen events in Quartermaster Harbor (QMH), a sensitive marine embayment of Vashon-Maury Island (VMI) in Puget Sound.

Water Suppliers on Vashon-Maury Island
This Groundwater Management Area has 23 Group A and 124 Group B Public Water Systems. The majority of the residents in this GWMA are serviced by the following Water Utility service areas:

This page is produced by the King County Groundwater Protection Program. To learn more about this group and its responsibilities, please read about the Groundwater Protection Program.

Related information  

• Vashon-Maury Island environment

Related agencies

• Department of Natural Resources and Parks
• Water and Land Resources Division

News and announcements

Report Card to the Community

Vashon Island water resources mailer