Wisconsin Administrative Code › Department of Natural Resources › NR 100-199 - Environmental Protection - General › Chapter NR 102 - Water Quality Standards For Wisconsin Surface Waters › Subchapter III - Waterbody Assessments and Reporting › Section NR 102.60 - Combined assessment procedure for phosphorus

Current through June 24, 2024
(1) GENERAL.
(a) This section establishes a combined
				  assessment approach for making total phosphorus attainment determinations for
				  surface waters in cases specified in par. (b). This approach is designed to
				  account for variability in how waterbodies respond to phosphorus. The combined
				  approach evaluates a waterbody's quality by considering the total phosphorus
				  concentration in the surface water in conjunction with an evaluation of the
				  phosphorus response indicators specified in subs. (2) to (4). The phosphorus
				  response indicators characterize the condition or abundance of aquatic
				  organisms that are responsive to total phosphorus to determine whether aquatic
				  life and recreation uses are being met. Together, the total phosphorus criteria
				  and response indicators may be used to determine whether the phosphorus water
				  quality standards are attained or whether the waterbody should be listed as
				  impaired for total phosphorus on the section 303 (d) list.
(b)
1. If a
				  waterbody's calculated total phosphorus concentration exceeds its total
				  phosphorus criterion using the assessment procedure under s.
				  NR
				  102.07 and the waterbody's calculated phosphorus
				  concentration is within the combined assessment range shown in Table 10, the
				  department may make the total phosphorus attainment or impairment determination
				  using phosphorus response indicators specified in subs. (2) to (4) if
				  sufficient biological data are available to conduct these assessments. In that
				  case, the following decision protocols apply:
a. A waterbody that attains all of its
				  applicable phosphorus response indicators under subs. (2) to (4) may be
				  excluded from the section 303 (d) listing of waters impaired for phosphorus.
Note:
If a waterbody is not considered
					 impaired using the combined approach, it may be a candidate for a less
					 stringent phosphorus site-specific criterion under ch. NR 119. If a waterbody
					 attains its phosphorus criterion but one or more phosphorus response indicators
					 are not attained, it may be a candidate for a more stringent site-specific
					 phosphorus criterion under ch. NR 119.
b. If a waterbody does not attain one or more
				  of the applicable phosphorus response indicators in subs. (2) to (4) or if the
				  department does not have sufficient data to evaluate all of the applicable
				  response indicators, then the waterbody shall be considered impaired for total
				  phosphorus and the department shall propose inclusion of the waterbody on the
				  section 303 (d) list as not attaining its phosphorus criterion. As part of the
				  public comment period for the section 303 (d) list, the department shall
				  provide a list of waterbodies needing additional data to determine whether
				  phosphorus response indicators are met. If sufficient phosphorus response
				  indicator data becomes available in the future, the waterbody may be
				  reassessed.
2. If a
				  waterbody's calculated phosphorus concentration exceeds its total phosphorus
				  criterion using the assessment procedure under s.
				  NR
				  102.07 and the waterbody's calculated phosphorus
				  concentration also exceeds the upper limit of the combined assessment range
				  shown in Table 10, then the waterbody shall be considered impaired for total
				  phosphorus regardless of attainment of phosphorus response indicators, and the
				  department shall propose to include the waterbody on the section 303 (d) list.
Table 10
Range for applying combined assessment for total
					 phosphorus1
Waterbody type
Total phosphorus criterion
								  (ug/L)
Combined approach
								  range2 (ug/L total phosphorus)
Stream or its impounded flowing
								  water
75
75 to [LESS THAN]150
River or its impounded flowing
								  water
100
100 to [LESS THAN]200
Unstratified reservoirs, unstratified drainage or
								  seepage lakes
40
40 to [LESS THAN]60
Stratified reservoirs, stratified drainage
								  lakes
30
30 to [LESS THAN]45
Stratified seepage lakes
20
20 to [LESS THAN]30
Two-story fishery lakes
15
15 to [LESS THAN]22.5
1 To determine whether a
					 waterbody falls into the combined approach range, compare the lower confidence
					 limit of the waterbody's two-sided 80% confidence interval around the mean (for
					 lakes/rivers) or median (for rivers/streams) total phosphorus concentration to
					 the ranges in the table.
2 For streams and rivers the
					 combined criteria range is between the applicable total phosphorus criterion
					 and two times that criterion. For lakes, the range is between the applicable
					 total phosphorus criterion and 1.5 times that criterion. If a waterbody has an
					 approved site-specific phosphorus criteria, the combined criteria range for
					 that waterbody shall be calculated using these multiplication factors.