Crook County Groundwater Investigation

Overview

Since late summer of 2023, DEQ has been coordinating with Governor Kotek's office, Department of Geological and Mining Industry, Oregon Health Authority and Oregon Water Resources Department to address groundwater issues in Crook County.

Private well owners north of the city of Prineville have submitted concerns to multiple state agencies about their well water quality, including concerns for potential impacts on human health. The reports include concerns about drinking water quality and its impact on their health, household pipes, appliances and suitability for use by livestock and animals.

DEQ's top priorities

To adequately investigate groundwater issues in Crook County, DEQ's priorities are to oversee Knife River's groundwater investigation in partnership with DOGAMI. Additionally, DEQ will continue to support OHA as they complete their public health consultation.

While EPA has established maximum contaminant levels to protect the public against contaminants that present a risk to human health and secondary maximum contaminant levels for aesthetic considerations, such as scaling, taste and odor, that are not considered to present a risk to human health, these enforceable standards are for public water systems only. The quality and safety of drinking water from private domestic wells are not regulated by the Federal or State Government.

Knife River Sampling and Analysis Plan

In September 2024, DEQ and DOGAMI directed Knife River Corporation to conduct a groundwater investigation at the Knife River Woodward Mine. This investigation was to evaluate whether mining operations contributed to groundwater contamination or potential water quality impacts in nearby domestic drinking water wells. Quarterly sampling began in December 2025 and will run through 2026. 

• Read Knife River's state agency-approved Sampling and Analysis Plan.

Q4 2025 sampling results

In December 2025, Knife River's consultant conducted its first split water quality sampling as part of its sampling and analysis plan. DEQ conducted simultaneous split-sampling. Because this is the first data set in a series, it is too early to draw conclusions as to the source of contamination. While this initial sampling is a first step, completing Knife River's sampling and analysis plan is critical to understanding groundwater conditions.

During sampling, DEQ observed multiple instances in which the sampling methods employed by Knife River's consultant deviated from their approved sampling and analysis plan. DEQ and DOGAMI are holding Knife River responsible for implementing their sampling and analysis plan as written, including following sampling protocols for future sampling events.

• Read the Q4 DEQ Split Sample Field Report

Domestic drinking well sampling

Sampling domestic drinking water wells is an important first step in addressing water quality issues. DEQ hired an environmental consultant, Maul Foster and Alongi, to sample private drinking water wells in Crook County in the Fall of 2024 and Spring of 2025. The purpose of the domestic well water sampling was not to identify the source of any contaminants found, but to provide homeowners with drinking water quality information, and to provide the OHA with initial data to develop an area-wide public health consultation.