Denali Water Solutions agreed to pay $610,000 civil penalty — the first judicial biosolids-only settlement in EPA history — and implement a Soil Sampling and Agronomic Rate Calculation Protocol if resuming land application operations in Arizona or California.

Denali Water Solutions, LLC — Biosolids Over-Application (First Judicial Biosolids Settlement) (2024)

Outcome: Denali Water Solutions agreed to pay $610,000 civil penalty in the first-ever judicial settlement in the United States involving biosolids violations exclusively, and agreed to implement a documented Soil Sampling and Agronomic Rate Calculation Protocol if resuming operations in Arizona or California within five years.

Denali Water Solutions, LLC, a company providing biosolids (treated sewage sludge) land application services for wastewater utilities, violated Clean Water Act Section 405(e) at land application sites in Arizona and California. The violations involved applying biosolids to fallow fields above agronomic rates — the maximum amount of biosolids a field can absorb based on crop nutrient uptake — and failing to obtain or use reasonable site-specific information to determine appropriate application amounts. Over-application of biosolids at rates exceeding agronomic uptake causes excess nitrogen and phosphorus to leach into groundwater or run off into surface waters.

The settlement, announced November 12, 2024, required Denali to pay a $610,000 civil penalty and imposed a mandatory Soil Sampling and Agronomic Rate Calculation Protocol as a condition of any resumed operations in Arizona or California within the next five years. EPA characterized this as the first judicial settlement focused exclusively on biosolids violations under the Clean Water Act — a landmark in a regulatory space that had historically relied on administrative actions rather than court-entered consent decrees.

Biosolids land application is a widespread practice that benefits agriculture by returning nutrients to farm soil, but the practice requires precise management to avoid nutrient over-loading. Denali's violation reflects the tension between the economics of biosolids disposal — land application is far cheaper than landfilling — and the scientific precision required to apply biosolids within agronomic limits. The settlement establishes a precedent that biosolids applicators can face substantial federal civil penalties for agronomic rate violations.

Primary Source: Denali Water Solutions, LLC Clean Water Act Settlement Summary | US EPA