Ammonia WQS Variance Tools for Small Communities with Lagoon Wastewater Treatment Systems
In response to needs identified by state co-regulators and lagoon-utilizing communities, the EPA developed the Small Lagoon Community Economic Streamlining (SLCES) Tool and the Individual Lagoon Tool (ILT) as priority actions under the EPA’s 2022-2026 Lagoon Wastewater Treatment Action Plan. Both tools provide a user-friendly, streamlined way for a state, Tribe, or community to determine whether a water quality standards (WQS) variance is appropriate for a small community experiencing lagoon system compliance challenges related to ammonia. The tools are accompanied by an implementation document describing when each tool might be most useful and how to use the tools’ results to construct a WQS variance consistent with the EPA’s regulation.
On this page:
- Overview
- Small Lagoon Community Economic Streamlining (SLCES) Tool
- Individual Lagoon Tool (ILT)
- Applying the EPA’s Economic Analysis Tools to a WQS Variance for Ammonia for Small Lagoon Communities
- SLCES Tool and ILT Supporting Documentation
Overview
Small communities with lagoon wastewater treatment systems typically serve fewer than 3,000 people and frequently lack the necessary financial and technical resources to comply with the Clean Water Act (CWA). Many of these communities utilize lagoon wastewater systems as the only way to treat their community wastewater. Based on an analysis completed in 2022, the EPA found that over 4,500 of these facilities are discharging lagoon wastewater systems that do not rely on more advanced supplemental technology; this is about one-quarter of the nation’s Publicly Owned Treatment Works (POTWs) regulated by the CWA’s National Pollutant Discharge Elimination System (NPDES) program.
A lagoon community may be interested in a WQS variance when they are unable to comply with their ammonia water quality-based effluent limit (WQBEL) in an NPDES permit, and neither technological nor financial assistance is available to remedy the noncompliance issue, but incremental water quality progress can be made.
View the webinar below for an overview of how the ILT and the SLCES Tool can be used to streamline the economic analysis needed to demonstrate the need for a WQS variance. The webinar also provides a demonstration of each tool and discuss the EPA’s guidance on developing an ammonia WQS variance, where appropriate, based on the outputs from the tools.
Small Lagoon Community Economic Streamlining (SLCES) Tool
The SLCES Tool streamlines the information collection process for conducting the economic impact analysis for a WQS variance for publicly owned lagoon wastewater treatment systems for ammonia, following the EPA’s economic guidance for WQS. The SLCES tool can evaluate up to 1,000 lagoon communities at the same time with a minimum of user input.
The SLCES Tool User Manual describes how to use the SLCES Tool, and the tool’s assumptions and limitations.
Individual Lagoon Tool (ILT)
The ILT enables a user to conduct the economic impact analysis for a WQS variance for a publicly owned lagoon wastewater treatment system for ammonia, following the EPA’s economic guidance for WQS, streamlining the cost-estimation while allowing for the use of community-specific economic information. The ILT may be particularly useful where using the SLCES Tool may not accurately reflect community conditions.
Applying the EPA’s Economic Analysis Tools to a WQS Variance for Ammonia for Small Lagoon Communities
The following implementation document for the SLCES Tool and ILT describes when each tool might be most useful and how to use the tools’ results to construct a WQS variance consistent with the EPA’s WQS regulation.
SLCES Tool and ILT Supporting Documentation
Review the EPA’s methodology for developing the cost estimation models and the sources for the performance estimates for the three pollutant control technologies used in the ILT and SLCES Tool:
Learn about the EPA’s process for developing a statistical model that could predict the results of the Secondary Test analysis using readily available data from the United States Census Bureau, for inclusion in the Small Lagoon Community Economic Streamlining (SLCES) Tool: