Yakima County Wellhead Protection Plan

Yakima County’s water system consists of the former Terraced Estates Water Company (TEWC) and the former Country Club District Water Company (CCDWC). Yakima County assumed ownership and operation of the TEWC system in 1991, and the CCDWC system in 1994. The 2 systems were combined in 1996 and are now called the Terrace Heights Water System.

The County’s system consists of 6 source wells, 3 booster pump stations, 6 pressure reducing stations, 3 reservoirs for a combined storage of approximately 1.65 MG, approximately 134,000 lineal feet of distribution pipe ranging in size from 2- to 16-inch galvanized steel, uncoated steel, cast iron and PVC, and a telemetry system.
  • Well Number 1 is an emergency source and is not normally in use.
  • Well Number 2 was drilled in 1978 and pumps 270 gallons per minute.
  • Well Number 3 was drilled in 1993 and pumps 1,500 gallons per minute.
  • Well Number 4 was drilled in 1925 and pumps 400 gallons per minute.
  • Well Number 5 was drilled in 1946 and pumps 340 gallons per minute.
  • Well Number 6 was drilled in 1983 and pumps 340 gallons per minute.
The County has total certified water rights in the amount of 4,858 acre-feet. The County’s sources have historically provided high quality water.

Wellhead Protection Area Delineations
The County's wellhead protection areas (WHPA) were delineated using an analytical model. The table below summarizes the acreage covered by each WHPA.

Analytical Model Area (Acres)

Source 6-Month 1-Year 5-Year 10-Year
Well Number 1
 2.3 4.8 46.4 182.8
Well Number 2
 2.7 4.7 17.4 36.0
Well Number 3
 1.5 2.2 7.8 15.8
Well Number 4 and 5
 7.1 14.5 129.6 463.3
Well Number 6
 3.9 9.4 111.9 405.6

Inventory of Potential Contaminant Sources


After delineating the WHPAs associated with the County’s wells, an inventory of existing and potential sources of groundwater contamination (PDF) was compiled and mapped. High risk potential contamination sources located near the County's wells include underground storage tanks, leaking underground storage tanks, moderate risk businesses, and agricultural land which may be susceptible to pesticide use.

Contingency Plan


The County's contingency plan consists of the following components:
  • Susceptibility Assessments: The Washington State Department of Health (DOH) has ranked all of the County's wells as having a low susceptibility to contamination except for Well Number 5, which was ranked moderate.
  • Source Deficiencies: The County can currently meet the existing and 20-year projected maximum day demand with all sources in service as required by the DOH. However, if the County's largest well (Well Number 3) becomes contaminated, the County will not be able to meet its 20-year projected maximum day demand by approximately 700 gallons per minute. The County plans to drill a well or increase the pumping capacity of an existing well in the next 6 years to provide for additional source redundancy and source capacity.
  • Emergency Response: The County has developed an emergency response plan that includes an emergency call-up list and response procedures for spills, fires, and water supply contamination.
  • Short-Term and Long-Term Water Supplies: Bottled water and tanker trucks represent the most appropriate short-term alternative water supply for the County in an emergency situation. The County's water system is located 1-half mile from the City of Yakima and this intertie could also be explored as a short- or long-term water supply source. New source development, intertie development, and groundwater remediation are the most appropriate long-term alternatives.

Local Management Plan


Local management efforts adopted by the County include:
  • Posting of street signs at wellhead protection area boundaries
  • Distribution of literature
  • Notification of residences and businesses within the County's wellhead protection areas
View the Regional Management Plan page for more information.