DEQ reports nitrate in majority of sampled wells; two exceed EPA safe limit in Southern Deschutes County

The Oregon Department of Environmental Quality (DEQ) told the Deschutes County Board of Commissioners on Feb. 3 that a statewide groundwater sampling effort in Southern Deschutes County detected nitrate in 65 of 100 domestic wells sampled and that 3 wells exceeded the state action level of 7 milligrams per liter; 2 of those wells measured above the U.S. Environmental Protection Agency—s maximum contaminant level (MCL) for nitrate of 10 mg/L, the highest at 23 mg/L.

Why it matters: Nitrate is both a direct health concern at high levels and a tracer that can indicate partially treated wastewater reaching drinking water. County and DEQ officials said the data are a snapshot; a full DEQ laboratory analysis and a possible trends analysis are still pending and will be used to put the raw results in context for residents and public-health agencies.

DEQ—s Greg Swayland, regional solutions program, told the board DEQ sampled roughly 100 domestic wells in Southern Deschutes County in the most recent event (spring 2023 to spring 2024) and that prior monitoring in the area includes sampling campaigns in 1995, 2000, 2001, 2014 and other dates. Swayland said DEQ first forwards results and any health implications to affected well owners and refers exceedances to county public health and the Oregon Health Authority; DEQ is producing a laboratory report and expects that more complete analysis to take about nine to 12 months.

Sean Rochet, DEQ statewide on-site program manager, said the most recent sampling results generally 'didn't reveal anything we didn't expect' but confirmed DEQ is pursuing rulemaking to address on-site systems and nitrate concerns. Rochet said the rulemaking received legislative funding tied to sewer-availability and accessory dwelling unit (ADU) topics; the rules advisory committee is meeting and DEQ is considering changes that could allow or more broadly recognize specific on-site technologies that reduce nitrate.

County staff: Peter Gutowski, the county—s community development director, and Todd Cleveland, the county—s on-site wastewater manager, briefed the board on the county—s Southern Deschutes County Groundwater Protection Program annual report. Gutowski outlined long-term work in the La Pine subbasin: federal and state studies, partnerships with Central Oregon Intergovernmental Council (COIC) and NeighborImpact, loans and rebate programs, and investments the county estimates at more than $9 million directed to groundwater protection in the region.

What the county said about on-site systems: The county reported 1,200+ alternative treatment technology (ATT) systems installed to date in the subbasin and estimated the number will exceed 1,300 by summer; staff said that Deschutes County has approved more ATT systems than any other county in Oregon. The county also reported there are nearly 5,700 developed lots that still rely on conventional septic systems, creating a continuing nitrate load to the aquifer. County staff estimated roughly 300 of the ATT systems were upgrades or major repairs rather than new systems, but said that number is an estimate.

Discussion and next steps: Commissioners and staff discussed whether monitoring should focus on a repeat network of dedicated (monitoring) wells rather than voluntary domestic sampling, and raised the long-running policy option of pursuing a localized Goal 11 land use exception that would allow more area to be served by sewer. Commissioners and several speakers emphasized the costs and financing challenges of sewer buildout across widely dispersed rural lots, and suggested a neighborhood-by-neighborhood approach as more realistic than a single, large exception area. County staff said possible future funding sources include proceeds from county-owned land sales in the Newberry neighborhood and federal or state grants, but stressed those sources are not yet secured.

Public-health follow-up: DEQ and county staff said well owners who received nitrate results were notified and given referrals to public-health resources; no additional county-wide health action was announced at the meeting. DEQ emphasized the agency—s intent to complete a laboratory analysis and that a trend analysis (if completed) would provide additional context about long-term change in groundwater quality.

Ending: County and DEQ officials asked for continued partnership among local government, DEQ, state legislators and residents on monitoring, incentives for upgrades, and technical and financial assistance. Both agencies said more analysis is forthcoming and that outreach to residents and health referrals remain priorities.