Groundwater Protection

Groundwater = Drinking Water

Groundwater Protection Area Sign100 percent of Olympia's drinking water comes from groundwater. Activities on the surface of the land have the potential to contaminate and deplete our groundwater.

Drinking Water Protection Areas

Drinking Water Protection Areas (DWPAs) are large areas (of several square-miles) surrounding each of our water supply wells that mark their primary recharge areas. Federal, State, and county regulations, as well as Olympia's municipal code, are in place in these areas to protect our community's drinking water supply.

The City of Olympia has six established and one planned DWPA. Most of the land within our DWPAs is outside the Olympia city limits. The seven DWPAs include:

McAllister Wellfield
The McAllister Wellfield DWPA is located in north Thurston County about nine miles east of Olympia. The Wellfield supplies the City's entire water service area year-round, typically providing about 85 percent of the City's drinking water. The Utility developed the McAllister Wellfield in 2014 to replace the more vulnerable McAllister Springs source.

East Olympia
Three DWPAs in southeast Olympia protect three wells: Shana Park Well, Indian Summer Well, and Hoffman Well. Shana Park Well and Indian Summer Well are both treated and available for year-round use, although they are sometimes not used in the winter months. Hoffman Well is an untreated source, occasionally used on a seasonal basis. Together these wells provide up to about six percent of the City's water supply when they are operating.

Briggs Well
In East Olympia, a DWPA has been delineated for the planned Briggs Well, which is currently scheduled for completion in 2019. The well is planned to be located in the Briggs Village development near Ward Lake.

West Olympia
Two DWPAs in West Olympia protect three wells. Two wells in the Allison Springs DWPA provide about ten percent of the City's total supply, primarily between May and October. Kaiser Well is on standby only as an emergency supply.

How You Can Help Protect Our Groundwater

Report Spills Immediately

In the event of a large spill (such as from a tank truck or storage tank) call 9-1-1. For smaller spills, such as involving automotive, landscape, or household products call Thurston County at 360.867.2099.

Septic Systems

If you have questions about your septic system, call Thurston County at 360.867.2673.

Your Landscape Matters

Using low-maintenance native and drought-tolerant plants to create a sustainable landscape is the easiest way to help protect our groundwater. Download our Landscape Plans Packet for a variety of easily adaptable, pre-made landscape plans and helpful plant lists.

Fertilize Wisely

Nitrate from lawn fertilizers pose a major threat to our drinking water. If you want to fertilize your lawn, it's important to pick the right time and to use the right type and amount of fertilizer for long-lasting results that also protect our water resources.

  1. Pick the Right Time
    For a spring application, wait until mid-May or early June when heavy rains have passed so that less fertilizer will be wasted by seeping unused into the ground. Fertilizing at this time also helps avoid a growth surge when the lawn is already vigorously growing so you won't have to mow as often. In the fall, September or early October is also a good time to fertilize, before the heavy rains start.
  2. Pick the Right Product
    Fertilizer nutrients in slow-release forms are available to plants over a longer period of time, meaning fewer nutrients are wasted or lost as pollutants. Look for products that are organic or polymer-coated or are made from sulfur, isobutylidene diurea (IBDU), methylene urea, and "ureaform" and have at least 50% water-insoluble nitrogen.
  3. Choose the Best N-P-K Ratio
    Numbers like 8-3-1 or 32-3-3 are typically provided somewhere on the back of the bag. The first number tells you the percentage of Nitrogen (N) in the product. Look for a product that has a balance close to a proportion of 3-1-2.
  4. Use the Right Amount
    Compare your lawn's actual square footage with the treatable square footage on the fertilizer bag. Often times you will not need to use an entire bag.
  5. Only Use About 1 Pound of Nitrogen Each Time You Fertilize
    To figure out how to get 1 pound of Nitrogen on your lawn do the following calculation. Look at the first number in the N-P-K ratio on your bag. Divide 100 by this number. This number will tell you how much of the fertilizer needs to be applied to 1,000 square feet to supply 1 pound of actual Nitrogen. For most solid fertilizers, 1 pound equals about 4 cups of product.

    And get this! If you mulch-mow, grass clippings add about 1 pound of Nitrogen, so subtract an application or use 3/4 of a pound of Nitrogen each time.

Rules for New Developments

All non-exempt new developments within a Drinking Water Protection Area are required to meet certain standards to help prevent groundwater contamination.

For complete details or more information about any of the following requirements see OMC 18.32.200-18.32.240

Minimum Mitigation Standards

  1. A hazardous materials management (spill) plan is required if the project will be using, storing, handling or disposing of hazardous materials. The minimum quantity thresholds for this requirement and detailed elements of the spill plan are provided under OMC 18.32.235.
  2. Landscaping and irrigation standards of OMC 18.32.225 include the following:

    a. Restrictions on the use of highly water-soluble fertilizers.

    b. Limitations on total turf area and requirements for the use of native and drought-tolerant plants. See our Landscape Plans Packet for plant options.

    c. Irrigation systems designed and managed to maximize efficient use of water, with an irrigation consultation required when the system is installed.
  3. A report that inventories existing wells on the property and decommissioning procedures if needed.
  4. Granting City access to the property to provide outreach and informational materials, and to ensure compliance with these requirements.

Dedicated Groundwater Monitoring Well
A groundwater monitoring well may be required where storm water is infiltrated, or where other groundwater contamination risks or monitoring needs are identified. View details in the Engineering Design and Development Standards (EDDS)

Hydrogeological Reports
When the City determines that risks from a project or activity are not well known, a hydrogeological report may be required. This report provides City staff with information about site geology, groundwater quality and flow, surface water, and possible effects from the proposed project.

Outside City Limits?

Land within our Drinking Water Protection Areas that falls outside of the Olympia City limits is governed by either Thurston County of City of Lacey Codes.


Contact Donna Buxton at 360.753.8793 or