Groundwater & Wellhead Protection

Why Wellhead Protection?

Wellhead Protection is a pro-active approach to preventing contamination of groundwater used for drinking water supplies. Cleaning groundwater can often cost 100 times more than preventing the pollution in the first place.

Wellhead Protection (WHP) is a requirement for Group A Water Systems to protect the health of people using groundwater supplies for drinking water. The City of Redmond WHP Program is compliant with Chapter 246-290 of the Washington Administrative Code (WAC) and, therefore, the federal Safe Drinking Water Act.

Redmond’s Wellhead Protection Program staff evaluate and mitigate risks to groundwater by:

  1. Identifying groundwater resources at risk surrounding our municipal supply wells (the Critical Aquifer Recharge Area). 
  2. Identifying existing groundwater impacts and activities that have the potential to contaminate groundwater or reduce groundwater quantity.
  3. Developing strategies to prevent degradation or loss of groundwater resources from occurring.
  4. Monitoring to make sure a condition that could cause an unacceptable risk is not occurring.
  5. Managing existing impacts to ensure appropriate investigation and cleanup of natural resources.
When a potential impact or supply risk is identified, early warning to the Public Works Water Quality Division is issued before a municipal supply well can be adversely impacted. Wellhead Protection Program staff then work closely with the Water/Wastewater Division to meet Source Water Protection regulations.
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What is a Wellhead Protection Zone?

The Critical Aquifer Recharge Area (CARA) is divided into three Wellhead Protection Zones (Zones 1, 2, and 3). The zones are based on the time it takes a drop of water to travel from the point where it enters the aquifer to the point where it enters the nearest drinking water well. In Zone 1 groundwater takes 6 months or less to reach the nearest drinking water well. In Zone 2 it takes 1 year or less and in Zone 3 it takes up to 10 years to travel to the nearest drinking water well.

What Wellhead Protection Zone am I located in?

Wellhead Protection Zones Map

What is Groundwater?

Precipitation that seeps down through the soil filling the spaces between grains of sand and gravel is called groundwater. If there is enough groundwater for agriculture and municipal supply use it is termed an “aquifer”. Groundwater flows through the sand and gravel and eventually discharges into rivers and lakes.

Imagine building a moat for your sand castle at the beach. You do not have to dig very far before the sand is wet. Water pools up at the bottom of the hole. That water came from the small pore spaces between the sand grains. An aquifer is a sandy or gravelly layer in the ground where the pore spaces between the grains are saturated with water.

Hydrologic Cycle

The hydrologic cycle is how water evaporates, gathers in clouds and rains or snows onto the land. After it rains or the snow melts the water then either evaporates, is used up by the plants, runs off to streams, lakes, or the ocean, or infiltrates into the soil. Some of this infiltration will reach the underground water table and will recharge the aquifer. Recharge can also carry contaminants into groundwater from the land surface. Therefore, recharge is at the center of preventing pollution and maintaining supply both for drinking water and for freshwater habitats.

Hydrologic Cycle


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Groundwater in Redmond

About one third of Redmond's drinking water supply comes from a shallow groundwater aquifer located beneath City Center and extending east towards Novelty and Union Hill. In some places, you only have to drill 5 feet below ground surface before reaching groundwater. Our aquifer does not have a confining layer (a layer of material that impedes or prevents infiltration) to prevent potential adverse impacts from the surface from infiltrating.

Redmond operates five shallow municipal wells that pump between 3 and 4 million gallons of clean groundwater from the aquifer daily. This water is then delivered to homes and businesses in Redmond. Because of this valuable resource, Redmond’s water rates are among the lowest on the Eastside.

Groundwater Monitoring Program

In 2007, WHP staff implemented a Groundwater Monitoring Program. The program is designed to meet WHP goals for groundwater quality and quantity by detecting contamination and declines in water table levels before a supply well is adversely impacted. The backbone of the Groundwater Monitoring Program is a network of nearly 90 early-warning groundwater monitoring wells in the City’s 6.5 square-mile Critical Aquifer Recharge Area (CARA), which is centered in the downtown area. Wells have been installed at Municipal Campus, the Skate Park, Anderson Park, Bear Creek Park, Sunset Gardens Park, Perrigo Park, Luke McRedmond Landing Park, and in various right-of-ways.

The first groundwater monitoring event was completed in January 2007. Depth-to-water measurements were collected to measure water quantity and groundwater samples were collected to measure water quality. Groundwater monitoring and analysis continues on a semi-annual basis. The results are continuously analyzed by WHP staff to preserve the availability and suitability of our drinking water resource.

Contact: Jessica Pfundt at 425-556-2709 

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Groundwater Quality

WHP Program staff monitor groundwater wells throughout the Critical Aquifer Recharge Area to meet goals for groundwater quality and quantity by detecting contamination and declines in water table levels before a municipal supply well is adversely impacted.

Staff in Redmond’s Public Works Water Quality Office monitor the municipal supply wells. Check out Redmond's most current Water Quality Report for more detailed reporting on Redmond's drinking water and its latest lead and copper testing.

Contact: John Burtsche, 425-556-2819



A body of rock that is sufficiently permeable to conduct groundwater and to yield economically significant quantities of water to wells and springs.

Confining Layer

A body of impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers.

Critical Aquifer Recharge Area

Critical aquifer recharge areas are those areas with a critical recharging effect on aquifers used for potable water (area in which water reaches the zone of saturation by surface infiltration).


Water in a saturated zone or stratum beneath the surface of the land or below a surface water body.

Group A Public Water System

A water system in Washington State which meets the federal definition of a public water system. This is a water system with ten or more connections, or which serves an average of twenty-five or more persons per day for sixty or more days within a calendar year. WAC 246-290-020.


The movement of water into soil or porous rock.


The physical structure, facility, or device at the land surface from or through which ground water flows or is pumped from water-bearing formations.

Wellhead Protection Zone

Land areas delineated by the City for purposes of safeguarding groundwaters that supply, or potentially supply, drinking water to wells operated by the City.

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Reimbursement for Hazardous Waste Improvements

See if your business qualifies for reimbursement for hazardous waste improvements (including secondary containment).

See if you qualify