Wisconsin Administrative Code › Department of Natural Resources › NR 100-199 - Environmental Protection - General › Chapter NR 102 - Water Quality Standards For Wisconsin Surface Waters › Subchapter I - General › Section NR 102.07 - Assessing phosphorus concentration

Current through June 24, 2024
(1) DATA
				  REQUIREMENTS.
(a)
Lakes and
				  reservoirs.
The total phosphorus criteria specified in s. NR 102.06
				  (4) apply to samples taken near a lake or reservoir's deepest point, within 2
				  meters of the surface. For assessment purposes samples shall, whenever
				  possible, be taken at least once per month for 3 months during the sampling
				  period of June 1 to September 15. The department shall calculate a lake or
				  reservoir's arithmetic mean total phosphorus concentration using at least 2
				  years of data from the sampling period.
Note:
Reservoirs, multi-lobed lakes, or very
					 large lakes may need more than one sampling station to assess the
					 lake.
(b)
Flowing
				  waters.
The total phosphorus criteria specified in s. NR 102.06 (3)
				  apply to samples taken from the main channel near the area with greatest flow.
				  For assessment purposes samples shall, whenever possible, be taken at least
				  once per month for 6 months during the sampling period of May 1 to October 31.
				  The department shall calculate the median total phosphorus concentration for a
				  stream, river, or impounded flowing water using at least one year of data from
				  the sampling period.
(c)
Assessment timeframe for lakes, reservoirs and flowing waters.
1. In this paragraph, "weather-controlled
				  total phosphorus concentration" means a waterbody's mean or median total
				  phosphorus concentration during the applicable assessment period, estimated
				  from measured data while controlling for weather variability using a method
				  such as the department's Phosphorus Mixed Effects Regression calculation
				  method.
2. All representative data
				  from the most recent 5 years shall be used for assessments, but data from the
				  most recent 10 years may be used if representative of current conditions. If
				  fewer than the recommended number of samples in par. (a) or (b) are available,
				  the department may be able to make an assessment determination on a
				  case-by-case basis. The department may calculate a site's weather-controlled
				  total phosphorus concentration to correct for weather variability and use this
				  value to make an assessment determination in place of the mean or median
				  calculated under par. (a) or (b).
Note:
A mean total phosphorus concentration is
					 used for lakes or reservoirs; a median concentration is used for streams,
					 rivers, or impounded flowing waters. Total phosphorus data may be submitted and
					 weather-controlled concentrations can be obtained by contacting the department
					 at DNRSWIMS@wisconsin.gov for access to the department's SWIMS database. The
					 statistical computer programming script to run the Phosphorus Mixed Effects
					 Regression calculation can be obtained through the department's Water
					 Evaluation Section by contacting the department's call center at 1-888-WDNRINFo
					 (1-888-936-7463) or using options provided on its website at
https://dnr.wi.gov/contact/
.
Note:
The procedures in pars. (b) to (c) are
					 also used for determining upstream concentrations of phosphorus under s. NR
					 217.13 (2) (d) for purposes of calculating a water-quality based effluent limit
					 for a Wisconsin pollutant discharge elimination system (WPDES) permit.