DEQ: Nitrate found in 65 of 100 domestic wells in southern Deschutes County; county considers targeted sewer and treatment investments

The Oregon Department of Environmental Quality reported Thursday that its 2023–24 sampling of 100 domestic wells in southern Deschutes County detected nitrate in 65 wells; three samples exceeded the Oregon state action level of 7 milligrams per liter, and two exceeded the U.S. Environmental Protection Agency's maximum contaminant level of 10 milligrams per liter, with the highest reading at 23 milligrams per liter.

Those findings, presented at the Deschutes County Board of Commissioners meeting in the Allen Room, are based on raw lab results that DEQ said are still undergoing full quality assurance and analysis before a formal report is published later this year. "Results detected nitrate in 65 of those wells and 3 were above the state action level of 7 milligrams per liter," said Greg Sweeland, who works in DEQ's Bend office and helped lead the sampling project. He said DEQ provides results to well owners and refers exceedances to public health partners.

A nut graf: The data represent a voluntary snapshot of domestic wells and are not yet a full trend analysis, but commissioners and DEQ staff said the results reinforce long-standing concerns about nitrate loading in the La Pine subbasin and the limits of current local and state tools to reduce long-term contamination.

DEQ sampled private domestic wells in spring 2023 through spring 2024; the agency emphasized the sampling was largely voluntary. "The recent sampling event doesn't really show us anything that we didn't expect," said Sean Rochet, DEQ statewide on-site program manager based in Bend, adding that the agency is preparing rulemaking tied to sewer availability, accessory dwelling unit (ADU) issues and technology allowances that could affect nitrate management statewide.

County staff and commissioners noted monitoring design matters: a subset of wells has been resampled across decades, while many new samples are single-event domestic well tests. DEQ said roughly 22 wells in the network have been sampled four times and some up to five times, providing a limited long-term series but not a comprehensive, science-designed monitoring network.

Deschutes County Community Development Director Peter Gutowski and on-site wastewater manager Todd Cleveland reviewed local actions: the county has installed more than 1,200 alternative treatment technology (ATT) systems to reduce nitrate loading and expects to surpass 1,300 by summer; about 6,900 lots in the subbasin are developed and nearly 5,700 still use conventional septic systems, the county said. Gutowski called for annual reporting and said prior investments and partnerships total more than $9 million for groundwater protection projects.

Commissioners and staff discussed ways to accelerate reductions in nitrate loading: narrowed, neighborhood-scale sewer extensions, targeted incentives or loan programs to upgrade septic systems, and potential state or federal funding. Commissioners raised the county's prior effort to seek a Goal 11 exception to enable concentrated sewer projects and said such efforts must be smaller and more economically feasible if pursued again.

DEQ said a full, peer-reviewed report and any trend analysis likely will take nine to 12 months; meanwhile the agency notifies owners of individual exceedances and refers them to county and state public-health partners. DEQ staff noted the agency has limited enforcement tools and said recent state rulemaking and proposed legislation aim to improve monitoring and partnership mechanisms.

Ending: County officials asked DEQ and state partners for follow-up on the highest individual exceedances and urged development of a repeatable, science-based monitoring plan. Commissioners said they will continue to explore targeted infrastructure and funding options and reconvene on new data and legislative opportunities when available.