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Groundwater/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 local governments 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:
- Identifying groundwater resources at risk surrounding our municipal supply wells (the Critical Aquifer Recharge Area).
- Identifying existing groundwater impacts and activities that have the potential to contaminate groundwater or reduce groundwater quantity.
- Developing strategies to prevent degradation or loss of groundwater resources from occurring.
- Monitoring to make sure a condition that could cause an unacceptable risk is not occurring.
- Managing existing impacts to ensure appropriate investigation and cleanup of natural resources.
When a potential impact or supply risk is identified, Wellhead Protection Program staff then work closely with the Water/Wastewater Division to meet Source Water Protection regulations before a municipal supply well can be adversely impacted.
Redmond recently updated groundwater/wellhead protection areas using robust computer modeling. The updated areas are called Critical Aquifer Recharge Areas (CARA) and were adopted April 16, 2019.
As part of the update, Redmond convened a Sounding Board of people with diverse perspectives who learned about the groundwater model, participated in a series of meetings and helped make decisions related to some model settings.
CARA I and CARA II are areas are where the aquifer is vulnerable to contamination, and where infiltration is important for replenishing, or recharging, the groundwater supply. These special protection areas are based on the time it takes for groundwater to travel to a municipal supply well.
- CARA I represents the area where groundwater takes up to five years to travel to a municipal supply well.
- This is the area most vulnerable to contamination from pollutants.
- CARA II represents the area where groundwater takes up to 10 years to travel to a municipal supply well, plus additional sensitive areas.
CARA I and CARA II have requirements for development and businesses that help protect groundwater in CARA I and II.
Beneath the Downtown, Avondale Rd and southeast Redmond areas lie sand and gravel that was deposited long ago by glaciers and rivers. Within the tiny spaces of this geologic material flows groundwater that supplies 40% of Redmond’s drinking water. Municipal supply wells pump groundwater from this shallow water resource, called an aquifer. It’s then treated for safety and delivered as drinking water.
The aquifer is replenished by precipitation and surface water that infiltrates down through the soil. Since pollutants such as oil and chemicals can also infiltrate down to groundwater in the aquifer, special protection areas are established to keep municipal supply wells safe from contamination.
Your business can help protect groundwater by:
- Storing hazardous materials in secondary containment and cover.
- Staging spill kits at all hazardous materials storage areas and loading/unloading areas.
- Having a Spill Plan - Train employees what to do and who to call in the event of a spill.
- Cleaning up spills immediately and reporting to the Spill Hotline.
- Minimizing use of toxic cleaning solvents and switching to safer alternatives. Visit the Washington Department of Ecology Safer Alternatives page for more information.
For a FREE spill kit, help creating a site-specific Spill Plan, or help switching to a safer chemical alternative, contact Pollution Prevention Staff.
Since the approval of the Wellhead Protection Program by City Council in 2003, City staff have developed core program elements to protect groundwater through pollution prevention, technical assistance, risk assessment activities and groundwater monitoring.
Groundwater monitoring helps ensure the quality of our drinking water through quality testing and water level measurements in a network of approximately 90 monitor wells. Monitor wells are distributed throughout the Downtown, Avondale and southeast Redmond areas. Twice a year, about a third of these wells are tested for groundwater quality and all of the wells are measured for depth-to-water. These data are evaluated by City staff to understand the health of the aquifer, the groundwater’s elevation below the ground and the direction the groundwater flows.