Site-specific water quality criteria

Site-specific water quality criteria differ from site-specific water quality standards. A water quality criterion (WQC) may be developed when a toxic pollutant in surface water or fish lacks a numeric standard in Minn. R. 7050.0220, 7050.0222, 7050.0227 or 7052.0100. The MPCA is authorized to develop a numeric WQC that applies specifically to the water body or region where the pollutant is found, using data from that water body or region. The methods for developing WQC are in Minn. R. 7050.0217, 7050.0218 (7050.0219 for human health) and 7052.0110. WQC can be used to determine the status of surface waters (impaired or not) and can be applied in permits and at remediation sites following the procedures in Minn. R. 7050.0218, Subp. 2.  

The time to develop and implement a WQC is less than developing a water quality standard (WQS) that applies statewide. A WQC is developed using a smaller dataset specific to the water body or region where the criterion or criteria (e.g., one applicable in water and one in fish-tissue) will be applied, and the public review requirements are less involved than for statewide WQS, which must be adopted and promulgated into Minnesota Rule following Minnesota’s Administrative Procedures Act. In addition, WQC do not require EPA approval.  

WQC are typically developed when a pollutant is identified in surface water that is of local or regional concern, or in situations where a regulatory limit is needed for permitting or at remediation sites. For example, the MPCA developed WQC for PFOS and PFOA, two perfluorinated chemicals that were released in the eastern part of the Twin Cities Metropolitan Area (TCMA) and found in groundwater, drinking water, and the Mississippi River. 

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Water-quality criteria for PFOA and PFOS

From 2006 to 2007, the MPCA, with technical assistance and reports provided by STS Consultants, LTD., developed ambient surface-water quality criteria (WQC) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). The methods that were used to develop these criteria were published in Minnesota Rules, Chapter 7050. This effort led to site-specific WQC for Lake Calhoun (now Bde Maka Ska) and Mississippi River Pool 2.