Assessment Summary
The Class A1 use was assessed (monitored) as “fully supported.” The Class BLW use was assessed (evaluated) as “WINOFI” due to nuisance blooms of algae and re-suspension of sediment based on historical information from fisheries. Current water quality results indicate full support of the use, therefore, the Class BLW "WINOFI" will remain implace for the 2024 assessment cycle. All other designated uses were “not assessed.”
Note: A TMDL for algae and turbidity at Trumbull Lake was prepared by DNR and approved by EPA in 2006. Because all Section 303(d) impairments identified for the current assessment/listing cycle (algal growth, turbidity, and pH) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved.)
Assessment Explanation
Data Sources:
|
Data Source
|
Data Source ID
|
Data Type
|
Data Age
|
Site ID
|
Site
Name
|
Site
Description
|
|
Iowa DNR
|
6
|
WQ
|
CY 2018-2021
|
22210001
|
Trumbull
Lake Max Depth
|
|
Class A1 - Indicator Bacteria: No Data
Class A1 - pH:
|
Site ID
|
Data Source ID
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Mean Value
|
# Violations
|
Violations needed for impairment
|
Violates Significantly >10% Rule?
|
Assessment Type
|
Support Level
|
|
22210001
|
6
|
10 / 2
|
7.8
|
8.7
|
8.2
|
0
|
3
|
NO
|
Mon
|
Full
|
Class A1 - Lake TSI’s:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Median Value
|
Median TSI Violation?
|
Assessment Type
|
Support Level
|
|
22210001
|
6
|
Chlorophyll a TSI
|
16 / 4
|
37
|
84
|
54
|
NO
|
Mon
|
Full
|
|
22210001
|
6
|
Secchi TSI
|
15 / 3
|
55
|
80
|
70
|
NA
|
NA
|
NA
|
|
22210001
|
6
|
Total Phosphorus TSI
|
16 / 4
|
57
|
89
|
77
|
NA
|
NA
|
NA
|
|
22210001
|
6
|
Inorganic suspended solids
|
5 / 1
|
0.06
|
15
|
3.5
|
NA
|
NA
|
NA
|
The TSI value for Secchi depth is not used to evaluate the
attainment of aquatic life goals in shallow lakes. Due to the depth of these
shallow lakes, TSI values for Secchi depth can be misleading. In some
instances, the Secchi disk remains visible at the bottom of the lake and the
depth of the lake is recorded as the Secchi depth. In these instances, water
clarity may be sufficient to support the Class B(LW) uses, but the index value
is limited by the depth of the lake. Thus, the combination of total suspended
solids and chlorophyll a will be used to determine whether or not the Class BLW
uses are impaired in these shallow systems.
- The 4a turbidity impairment will be removed based on the inappropriate
of Secchi results in shallow lake systems. Additionally, the results of the Submerged
Aquatic Vegetation information show attainment.
- DNR's assessment methodology indicates that a TSI value less
than or equal to 63 are necessary to suggest de-listing of an impairment.
The chlorophyll a TSI value for the 2002 assessment listing cycle was 80, which
based on DNR's assessment/listing methodology indicated an impairment based on
the narrative criteria protecting against aesthetically objectionable conditions.
Because the TSI value for the 2024 assessment/listing cycle is less than or
equal to the delisting trigger of 63 (median TSI value for chlorophyll a was
54), based on DNR's methodology, these values suggest "full support"
of the Class A1 uses protecting against aesthetically objectionable conditions
and the impairment (5a) for chlorophyll a is suggested for delisting for the
2024 assessment/listing cycle.
Class BLW - Binomial Parameters:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Mean Value
|
# Violations
|
# Acute / Chronic Violations
|
Violations needed for impairment
|
Violates Significantly >10% Rule?
|
Assessment Type
|
Support Level
|
|
22210001
|
6
|
Dissolved Oxygen
|
15 / 3
|
4.37
|
16.05
|
9.82
|
1
|
NA / NA
|
4
|
NO
|
Mon
|
Full
|
|
22210001
|
6
|
pH
|
10 / 2
|
7.8
|
8.7
|
8.2
|
0
|
NA / NA
|
3
|
NO
|
Mon
|
Full
|
|
22210001
|
6
|
Temperature
|
15 / 3
|
11.8
|
26.7
|
20.5
|
0
|
NA / NA
|
4
|
NO
|
Mon
|
Full
|
Class BLW - Protection of Submerged Aquatic Vegetation:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Median Value
|
Median Value = SAV
|
Assessment Type
|
Support Level
|
|
22210001
|
6
|
Total suspended solids
|
16 / 4
|
0.6
|
70
|
9.2
|
NO
|
Mon
|
Full
|
Guidelines for wetland assessment from the Upper Mississippi
River Conservation Committee’s Water Quality Technical Section (2003) state
that the overall median suspended solids concentration during the growing
season of less than 30 mg/L is necessary to provide sufficient water clarity to
support the growth of submersed aquatic vegetation in wetlands and shallow
lakes. High levels of total suspended solids impede the growth of submersed
aquatic vegetation (SAV). Submersed aquatic vegetation is critical to the
health of wetland and shallow lake ecosystems. The elimination of SAV can
degrade habitat quality such that undesirable aquatic species such as
cyanobacteria, common carp, and fathead minnows dominate. As such, the
suppression of SAV constitutes a violation of Iowa’s narrative water quality
criteria protecting against undesirable or nuisance aquatic life.
- The 4a turbidity impairment will be removed based the results of the median Submerged Aquatic Vegetation of 9.2mg/L. This if well below 30 mg/L required to delist based on the SAV.
Class BLW - Toxic Parameters:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Maximum Value
|
Mean Value
|
Median Value
|
# Acute / Chronic Violations
|
>1 Acute / Chronic Violation
|
Assessment Type
|
Support Level
|
|
22210001
|
6
|
Ammonia
|
5 / 1
|
0.025
|
0.02
|
0.02
|
0 / 0
|
NO
|
Evaluated
|
Full
|
Class HH - No Data
