Groundwater Management Plan

March 2, 2022 Information Session:

Roughly 30 Bainbridge Island residents got an update March 2 on the Groundwater Management Plan (GWMP).

Hydrogeologist Maureen Whalen answered questions that focused on what the GWMP will entail, how the GWMP will connect with the City's water infrastructure projects, and how the City ensures a safe water supply. Prior to answering questions, Whalen shared a presentation on what goes into a groundwater management plan, our current understanding of the groundwater system, and how we use groundwater for the drinking water supply on the island. The City is creating the GWMP to develop a communitywide understanding of our groundwater resources, to reduce and adapt to climate change impacts and ensure clean and sufficient groundwater. Access the meeting recording in the following link: GWMP meeting recording.

As a next step, staff will:

Fill data gaps in our understanding of how groundwater is used for drinking water supply and how land use affects groundwater quality;
Update our water monitoring report, including evaluating/updating the monitoring network; and
Work with advisory committees and stakeholders to draft the GWMP.

Project Overview

Bainbridge Island residents, workers and visitors rely on groundwater for all water supply needs, from drinking water and dishwashers to toilets and garden watering. Groundwater also plays a vital role in supporting healthy streams and wetlands.

The City is developing a Groundwater Management Plan (GWMP) that will take an islandwide approach to managing our precious groundwater resource and will serve as a document that can be adapted as our needs change. The plan will include a summary of what we know about the island’s geology; groundwater systems; streams, lakes, and wetlands; climate and climate change projections; land use; and population projections.

What is groundwater?

Groundwater is water in saturated ground (bedrock or sediments) that flows from recharge areas to discharge into springs, seeps, shoreline or wells or deeper into the subsurface. If you were able to take a giant knife and slice through the water-filled layers of sediment (mixtures of clay, silt, sand, and gravel) underlying Bainbridge Island, you would see four major aquifers.

Most of the island’s residents and businesses take water from those four aquifers which can be as deep as 1,000 or more feet below the ground.

COBI Groundwater Management Program