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Lower Yakima Valley Groundwater

Local, state, and federal agencies – including the EPA – are working with dairies in Washington's Lower Yakima Valley to address sources of nitrate contamination in groundwater.

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EPA is responding to community concerns in Washington’s Lower Yakima Valley about high nitrate levels in residential drinking water wells and the potential for disproportionate impacts on low income and minority rural populations, local, state, and federal agencies collaborated to develop a Preliminary Assessment and recommendations for moving forward.

One of the recommendations was to develop new projects that could help to identify sources of the contamination in groundwater supplies.

In accordance with this recommendation, EPA conducted sampling in 2010 as part of a study to identify potential sources of nitrate contamination in local groundwater and residential drinking water wells. EPA issued a report in March 2013 entitled, Relation Between Nitrate in Water Wells and Potential Sources in the Lower Yakima Valley. The study concluded that several dairies in the report were likely sources of elevated nitrate levels that were measured in residential drinking water wells downgradient of the dairies.

In December 2012 and January 2013 EPA installed and sampled 10 groundwater monitoring wells in the vicinity of the Yakima Valley dairies that were included in the 2010 study. Data collected by EPA from the monitoring wells confirmed that that the dairies are a source of nitrate contamination to the groundwater beneath and downgradient of these dairies. More recent and extensive data collected by the dairies under the Consent Order affirm this conclusion.

Why is Nitrate a Concern?

Nitrate is an "acute contaminant" meaning that one exposure can affect a person's health. Too much nitrate in your body makes it harder for red blood cells to carry oxygen.

Most people recover quickly after being exposed to nitrate, but it can be very dangerous for infants and some adults. Infants exposed to high amounts of nitrate may develop a potentially fatal condition known as "blue baby syndrome."

EPA's drinking water standard - or “maximum contaminant level” (MCL) - for nitrate is 10 mg/L (parts per million, or ppm). Unlike many other substances for which a standard has been set by EPA, there is no “safety factor” built into the nitrate MCL.

Learn more about nitrate:

Groundwater Management Area (GWMA)

EPA is also working with the Lower Yakima Valley Groundwater Management Area advisory committee to develop a comprehensive plan to reduce nitrate contamination in groundwater to below drinking water standards.

For more information, visit Lower Yakima Valley Groundwater Management AreaExit

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Consent Order

In March 2013, EPA and several dairies in the Lower Yakima Valley area signed a legal agreement called a Consent Order (see Documents below) to address sources of nitrate contamination in groundwater near and downgradient of the dairies’ facilities.

In signing the Consent Order, the dairies agreed to:

  1. Provide an alternate source of drinking water for neighbors within one mile down gradient of the dairies whose wells have levels of nitrate above EPA’s drinking water standard of 10 mg/L, or “parts per million” (ppm).
  2. Conduct soil and groundwater testing at each dairy to evaluate if nitrogen sources are being controlled.
  3. Take steps to control nitrogen sources (manure and commercial fertilizer) at their facilities.

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Additional Documents

Consent Order Plans and Reports

(Please note the new URL for this link as of 8/1/19) EPA-approved plans and reports developed in accordance with the Consent Order, including:

  • Groundwater monitoring data reports.
  • Irrigation water management plans.
  • Manure application field management plans.
  • Soil data reports.
  • Field capacity soil test reports.
  • Cow Palace lagoon work plan.
  • Contractor qualifications.
  • Monthly progress reports.

March 2013 Report Supplemental Information

(Please note the new URL for this link as of 8/1/19) Supplemental information related to EPA's March 2013 assessment report, including public input and EPA's responsiveness summary.

Reports by Other Agencies

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