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Oregon Health Authority

Nitrate testing, treatment, and water delivery for the Lower Umatilla Basin

The Oregon Health Authority (OHA) is working with its partners the Oregon Department of Human Services, Morrow County Public Health Department, Umatilla County Health Department, and community based organizations to provide free safe water services to households in northern Morrow and northwestern Umatilla counties. This is the area known as the Lower Umatilla Basin Groundwater Management Area (LUBGWMA). The maps below show the results of laboratory tests for nitrate in well water. The tables lower on the page provide the same information by the numbers, along with tables listing the number of households that have had water treatment systems installed, and households receiving bottled water deliveries.

For more information about the data that OHA is collecting related to domestic well testing in the Lower Umatilla Basin, please read this memo from Gabriela Goldfarb, OHA’s Environmental Public Health Section Manager.


All nitrate test results

All Nitrate test reults

Nitrate test results at or above 10 mg/L

Nitrate test results at or above 10 mg/L

Nitrate test results 5 mg/L to 9.99 mg/L

Nitrate test reults 5 mg/L to 9.99 mg/L

Nitrate test results below 5 mg/L

Nitrate test reults below 5 mg/L  

Summary tables updated September 30, 2024

Household Nitrate Test Results

Nitrate Range Morrow Umatilla Total
0 to 4.99 mg/L 226
725
951
5 to 9.99 mg/L 123
296
419
10 to 24.99 mg/L106
212
318
At or above 25 mg/L 125
 69
194
TOTALS 580
1302
1882

Households with Nitrate Test Results At or Above 10 mg/L

Nitrate Range Morrow Umatilla Total
10 to 24.99 mg/L 106
212
318
At or above 25 mg/L 125
69
194
TOTALS 231
281
512
Total high results as percent of all samples 40% 22% 27%

Water Treatment Installations

Important note: The table below shows all treatment systems installed by OHA vendors based on test results from OHA contract laboratories starting in 2023. In addition to the systems installed in Morrow County reported below, as of August 31, 2024, OHA's treatment vendors have also installed four treatment systems in households tested only for nitrates by a laboratory contracted by Morrow County in 2022.

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October 1, 2024:  We are working on an update for reporting installs of reverse osmosis systems. These numbers will be updated later this month. 
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Morrow Umatilla Total
82
55
137
100% of eligible
30% of eligible
52% of total eligible
Additional Notes
  • Reverse osmosis water treatment systems are certified to remove nitrate only up to approximately 25 mg/L, so are only effective in households testing between 10 to 25 mg/L nitrate. Households with water testing at or above 25 mg/L must rely on bottled water delivery. Plumber workforce constraints have limited the pace of installations.
  • The table above shows that 100% of households tested by OHA laboratories to date that are eligible for treatment system installation because their nitrate levels tested between 10-24.99 mg/L have had treatment systems installed. We are aware of a number of households tested by Morrow County in 2022 that may be eligible for treatment systems but have not yet responded to multiple efforts to contact them.
  • For additional information on numbers reported above, please click here to see a memorandum of explanation. 

Households Receiving Water Delivery

Morrow Umatilla Total
292
231
523



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