MPCA Issues SSS Framework for Wild-Rice Sulfate Standard

Originally published in the January/February 2024 issue of Bench & Bar of Minnesota Environmental Law Update, Minnesota State Bar Association.

In December 2023, the Minnesota Pollution Control Agency (MPCA) released its "Framework for Developing and Evaluating Site-Specific Sulfate Standards for the Protection of Wild Rice." The framework is the agency’s latest step to address the implementation of Minnesota’s Class 4A 10 mg/L sulfate water quality standard in Minn. R. 7050.0224, subp. 2, adopted in 1973, which applies to Class 4A waters “used for production of wild rice during periods when the rice may be susceptible to damage by high sulfate levels.” MPCA undertook an expansive rulemaking in the late 2017 to revise the wild-rice sulfate standard and identify waters subject to the revised standard. However, following an adverse administrative-law-judge report, MPCA abandoned the rulemaking in 2018. Since then, MPCA has issued various statements regarding how the agency will implement the sulfate standard and has identified close to 2,400 waters MPCA has determined are “used for production of wild rice” and thus subject to the standard. This list includes 32 water bodies the U.S. EPA in 2021 added to Minnesota’s 2020 Impaired Waters List due to measured sulfate levels in excess of 10 mg/L. Presumably recognizing the current paucity of feasible sulfate treatment technologies, the MPCA in 2023 initiated a series of public meetings to help the agency develop a framework for regulated parties seeking a less stringent site-specific standard (SSS) for sulfate in a particular waterbody.

MPCA’s Framework: (1) outlines the process of applying for a SSS, including state and federal review; (2) describes MPCA’s interpretation of the wild rice beneficial use protected by the sulfate standard; and (3) identifies the monitoring and other information that must be developed to support a SSS application. Each of these is discussed below.

Process Involved in Seeking a SSS

The Framework indicates that MPCA will evaluate SSS applications under the standards of Minn. R. 7050.0220, subp. 7, which require the applicant to demonstrate that the proposed SSS is “more appropriate” then the existing sulfate standard and will protect the Class 4A wild-rice beneficial use. If MPCA determines a proposed SSS should be advanced, it will initiate a public notice and comment period and then send the SSS to the U.S. EPA for review under 40 C.F.R. § 131.21. EPA must then approve (within 60 days) or disapprove (within 90 days) the proposed SSS based on the standards for approving state water quality standards, e.g., whether the SSS protects the designated use and is based on sound scientific rationale. 40 C.F.R. § 131.11(a)(1). The SSS takes does not take effect until after it is approved by EPA.

MPCA’s Interpretation of the Wild Rice Beneficial Use

In the Framework, MPCA sets forth its interpretation of the beneficial use protected by the Class 4A sulfate standard. Under Minn. R. 7050.0224, subp. 2, Class 4A waters of the state “must be such as to permit their use for irrigation without significant damage or adverse effects upon any crops or vegetation usually grown in the waters or area.” The rule then creates a subclass of Class 4A waters to which the 10 mg/L sulfate standard applies, i.e., “water used for production of wild rice during periods when the rice may be susceptible to damage by high sulfate levels.” MPCA’s interpretation of the key phrase “production of wild rice” is that it refers not only to the intentional cultivation of wild rice in agricultural paddies, but also to wild rice in naturally occurring stands; the 10 mg/L sulfate standard, MPCA indicates, is intended “to protect the continued generation of wild rice biomass, and any proposal for a site-specific modification of that standard must demonstrate that the continued generation of wild rice biomass will be protected.” MPCA’s interpretation does not address the standard’s seasonal component, i.e., “during periods when the rice may be susceptible to damage by high sulfate levels.” The Framework notes that MPCA is “taking an expansive approach” to identifying waters that are “used for production of wild rice” and thus subject to the sulfate standard; for example, MPCA indicates that “documentation of current or historical wild rice presence—recorded observations, harvest histories, measurements of population extent or other wild rice growth metrics, or other reliable evidence—is sufficient to consider a waterbody to be a water used for the production of wild rice.”

Note that Minn. R. 7050.0224, subp. 1 creates a separate narrative nondegradation standard for “selected wild rice waters [that] have been specifically identified [WR]” in chapter 7050; the “quality of these waters and the aquatic habitat necessary to support the propagation and maintenance of wild rice plant species must not be materially impaired or degraded.” In the late 1990s, MPCA formally designated 24 waters as [WR] waters protected by this standard. See Minn. R. 7050.0470, subpart 1. In the Framework, MPCA states that it interprets the part 7050.0224 as making the 24 [WR] waters subject both to the narrative standard in part 7050.0224, subp. 1 as well as the 10 mg/L Class 4A sulfate standard.

Information Needed to Support a SSS Application

The bulk of the Framework focuses on the types of information MPCA will accept to support a successful SSS application. Much of the information relates to demonstrating that the beneficial use will be protected, which means that the proposed SSS “will allow wild rice to not only persist in the short term but also to sustain itself—undergo production across multiple growth cycles and generations—into the long-term future.” MPCA anticipates that the most SSS applicants will attempt to demonstrate that the existing ambient sulfate concentrations in a wild rice water above 10 mg/L supports wild rice and that this existing concentration should be the SSS. To make this demonstration, applicants must provide “long-term monitoring of both surface water sulfate concentrations and the wild rice population.” MPCA strongly recommends that “long term” wild-rice monitoring should involve collecting “consecutive annual population data spanning at least the most recent ten years or two boom-bust cycles, whichever is shorter.”

In the 2017 proposed wild rice rule, MPCA embraced a sediment-based equation to predict site-specific sulfate concentration values. The agency has now backed off that approach. The Framework indicates that while the equation as well as other aspects of sediment and porewater chemistry analysis can be considered as part of an SSS application, MPCA “does not support their use as a primary means to derive” the SSS.

The Framework directs SSS applicants to consider other types of wild rice information, including but not limited to:

• Historical data and information concerning the water’s wild rice population and the local water chemistry.
• Chemical, hydrological and biological data from on-site monitoring and recent studies to demonstrate consistency with current scientific knowledge.
• Sulfate levels within a larger geographic context.
• Non-sulfate confounding factors, both natural and anthropogenic, that may interfere with wild rice growth, e.g., modified hydrology, aquatic invasive species, competing vegetation, shoreline development, boat traffic, climate change. Note, however, MPCA’s position that even if these types of confounding factors inhibit wild rice growth, this cannot be a basis for a less stringent sulfate SSS.

While the Framework addresses primarily applications for a SSS that is less stringent than the 10 mg/L sulfate standard, it also notes that the Framework can be used to seek a SSS that is more stringent, which could arise when the wild-rice beneficial use is not being met. In this case, the applicant would need to demonstrate that excess sulfate is a primary cause of the non-attainment.

Finally, MPCA emphasizes that the Framework is simply guidance and should not be construed as a rulemaking proposal or as altering or superseding the statewide 10 mg/L Class 4A sulfate standard. For this reason, MPCA expects to “periodically update this document in response to new scientific findings or the emergence of other relevant information.”