EPA Announces Availability Of Draft Guidance For Implementing Water Quality Criterion For Methylmercury

EPA is seeking comments on a draft guidance for implementing the water quality criterion for methylmercury. The document provides technical guidance to states, territories, and authorized tribes exercising responsibility under Clean Water Act (CWA) section 303(c) on implementing EPA's fish tissue-based methylmercury criterion recommendation.

According to an Aug. 9 Federal Register notice, the draft provides various technical and policy approaches to developing water quality standards for methylmercury and implementing these standards in Total Maximum Daily Loads (TMDLs) and National Pollutant Discharge Elimination System (NPDES) permits. EPA states that these approaches are recommendations only. States, territories and authorized tribes may choose to implement other technically sound approaches that are consistent with the CWA and EPA's implementing regulations.

This document describes analytical methods for determining the concentrations of mercury and methylmercury in both fish tissue and water. These methods can detect mercury and methylmercury in tissue and water at very low levels -- well below the levels of the previous criterion for mercury in the water column and the current criterion of methylmercury in fish tissue. This document also provides guidance for field sampling plans, laboratory analysis protocols, and data interpretation that is based on previously published EPA guidance on sampling strategies for contaminant monitoring. This guidance also describes how states can assess the attainment of water quality criteria and protection of designated uses by comparing sampling data to water quality criteria.

The guidance also discusses approaches for the development of TMDLs for waterbodies impaired by mercury. This includes approaches for TMDLs for waterbodies where much of the mercury is from atmospheric sources and suggestions regarding how such TMDLs can take into account ongoing efforts to address sources of mercury, such as programs under the Clean Air Act (CAA) and pollution prevention activities.

In a Jan. 8, 2001, Federal Register notice (http://www.epa.gov/fedrgstr/EPA-WATER/2001/January/Day-08/w217.htm), EPA announced the availability of its recommended water quality criterion for methylmercury. In the notice, EPA stated that it would develop associated procedures and guidance for implementing the criterion, and the draft guidance announced on Aug. 9 is the result.

The deadline for comments on the draft guidance is Oct. 10. The Federal Register notice can be accessed at http://www.epa.gov/fedrgstr/EPA-WATER/2006/August/Day-09/w6803.htm.

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