Minnesota Administrative Rules
Agency 167 - Pollution Control Agency
Chapter 7053 - STATE WATERS DISCHARGE RESTRICTIONS
EFFLUENT LIMITS AND TREATMENT REQUIREMENTS FOR DISCHARGES TO WATERS OF THE STATE
Part 7053.0135 - GENERAL DEFINITIONS

Universal Citation: MN Rules 7053.0135

Current through Register Vol. 49, No. 13, September 23, 2024

Subpart 1. Scope.

For purposes of this chapter, the following terms have the meanings given them.

Subp. 2. Terms defined in statute.

The terms "waters of the state," "point source," "sewage," "industrial wastes," and "other wastes," as well as any other terms for which definitions are given in the pollution control statutes, have the meanings given them in Minnesota Statutes, sections 115.01 and 115.41, with the exception that disposal systems or treatment works operated under permit or certificate of compliance of the agency are not "waters of the state."

Subp. 3. Seven-day ten-year low flow or 7Q10.

A. "Seven-day ten-year low flow" or "7Q10" means the lowest average seven-day flow with a once in ten-year recurrence interval. A 7Q10 is derived by identifying the lowest average flow for a seven-consecutive-day period from daily flow records for each year of record, from a continuous flow gauging station. The seven-day average low flow values for each year are arrayed in order of magnitude and fitted to a probability distribution. The 7Q10 is the stream or river flow that is equal to or exceeded by 90 percent of the values in the distribution.

B. The period of record for determining the specific flow for the stated recurrence interval, where records are available, shall include at least the most recent ten years of record, including flow records obtained after establishment of flow regulation devices, if any. Where stream flow records are not available, the flow may be estimated on the basis of available information on the watershed characteristics, precipitation, runoff, and other relevant data. The calculations shall not be applied to lakes and their embayments which have no comparable flow recurrence interval.

Subp. 4. Thirty-day ten-year low flow or 30Q10.

"Thirty-day ten-year low flow" or "30Q10" means the lowest average 30-day flow with a once in ten-year recurrence interval. A 30Q10 is derived using the same methods used to derive a 7Q10, and the guidelines regarding period of record for flow data and estimating a 7Q10 apply equally to determining a 30Q10, as described in subpart 3. The calculations shall not be applied to lakes and their embayments which have no comparable flow recurrence interval.

Subp. 4a. 122-day ten-year low flow or 122Q10. "122-day ten-year low flow" or "122Q10" means the lowest average 122-day flow with a once-in-ten-year recurrence interval. A 122Q10 is derived using the same methods used to derive a 7Q10, and the guidelines regarding period of record for flow data and estimating a 7Q10 apply equally to determining a 122Q10, as described in subpart 3.

Subp. 5. Commissioner.

"Commissioner" means the commissioner of the Pollution Control Agency or the commissioner's designee.

Subp. 5a. Control document. "Control document" has the meaning given in part 7050.0255, subpart 10.

Subp. 6. Effluent limit.

The terms "effluent limit" (equals "effluent limitation"), "point source," and "national pollutant discharge elimination system" have the meanings given them in part 7001.1020.

Subp. 7. Nonpoint source.

"Nonpoint source" means a land management or land use activity that contributes or may contribute to ground and surface water pollution as a result of runoff, seepage, or percolation and that is not defined as a point source under Minnesota Statutes, section 115.01, subdivision 11.

Subp. 8. Physical alteration.

"Physical alteration" means the dredging, filling, draining, or permanent inundating of a wetland. Restoring a degraded wetland by reestablishing its hydrology is not a physical alteration.

Subp. 9. Surface waters.

"Surface waters" means waters of the state, excluding groundwater as defined in Minnesota Statutes, section 115.01, subdivision 6.

Subp. 10. Other terms.

Other terms and abbreviations used in this chapter that are not specifically defined in applicable federal or state law must be construed in conformance with the context, in relation to the applicable section of the statutes pertaining to the matter, and current professional usage.

Statutory Authority: MS s 115.03; 115.44

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