Assessment Summary
The Class A1 uses are assessed (monitored) as “not supported” due to violations of the Class A1, BLW criterion for pH, and aesthetically objectionable conditions caused by poor water transparency and nuisance blooms of algae. The Class BLW uses are assessed (monitored) as “not supported” due to violations of the Class A1,B(LW) criterion for pH and multiple fish kills due to natural causes. All other designated uses are “not assessed”.
Note: A TMDL for organic enrichment at Crystal Lake was prepared by DNR and approved by EPA in 2002; thus, this waterbody was placed into IR Category 4a (TMDL approved). Because all of the Section 303(d) impairments identified for this assessment/listing cycle, it remains listed as Category 4a (TMDL approved) for this assessment/listing cycle.
Assessment Explanation
Sources of
Data:
|
Data Source
|
Data Source ID
|
Data Type
|
Data Age
|
Site ID
|
Site Name
|
Site Description
|
|
Iowa DNR
|
6
|
WQ
|
CY 2014-2018
|
22410001
|
Crystal Lake Max Depth
|
|
Class A1 -
Indicator Bacteria: No Data
Class A1 - pH:
|
Site ID
|
Data Source ID
|
# Samples / # Years
|
Maximum Value
|
Mean Value
|
Median Value
|
# Violations
|
% Violations
|
Significantly >10% Violations
|
Assessment Type
|
Support Level
|
|
22410001
|
6
|
15 / 5
|
9.25
|
8.76
|
8.7
|
2
|
13%
|
NO
|
Monitored
|
Full
|
- According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore, Crystal Lake will remain listed for the 2020 cycle as "not supported" its Class A1 uses due to pH.
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
|
|
22410001
|
6
|
Chlorophyll a TSI
|
15 / 5
|
36
|
82
|
66
|
YES
|
Monitored
|
Not
|
|
22410001
|
6
|
Secchi TSI
|
15 / 5
|
41
|
77
|
70
|
YES
|
Monitored
|
Not
|
|
22410001
|
6
|
Total Phosphorus TSI
|
15 / 5
|
56
|
86
|
76
|
NA
|
NA
|
NA
|
|
22410001
|
6
|
Inorganic suspended solids
|
15 / 5
|
0.4
|
7.5
|
2.2
|
NA
|
NA
|
NA
|
Class BLW -
Conventional Parameters:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Maximum Value
|
Mean Value
|
Median Value
|
# Acute / Chronic Violations
|
% Acute/ Chronic Violations
|
Significantly >10% Violations
|
Assessment Type
|
Support Level
|
|
22410001
|
6
|
Ammonia
|
15 / 5
|
0.662
|
0.12
|
0.04
|
0 / 0
|
0% / 0%
|
NO
|
Monitored
|
Full
|
|
22410001
|
6
|
Dissolved oxygen
|
15 / 5
|
12.4
|
7.7
|
7.5
|
NA / 3
|
NA / 20%
|
NO
|
Monitored
|
Full
|
|
22410001
|
6
|
pH
|
15 / 5
|
9.25
|
8.76
|
8.7
|
2 / NA
|
13% / NA
|
NO
|
Monitored
|
Full
|
|
22410001
|
6
|
Temperature
|
15 / 5
|
26.4
|
22.7
|
22.9
|
0 / 0
|
0% / 0%
|
NO
|
Monitored
|
Full
|
- According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore, Crystal Lake will remain listed for the 2020 cycle as "not supported" its Class BLW uses due to pH.
Class BLW -
Lake Planktonic Cyanobacteria:
|
Site ID
|
Data Source ID
|
# Samples
|
Maximum Cyanobacteria Wet Mass
|
Maximum Cyanobacteria % Composition
|
Median Cyanobacteria Wet Mass
|
Median Cyanobacteria % Composition
|
Median Cyanobacteria Wet Mass = 75th
Percentile
|
Assessment Type
|
Support Level
|
|
22410001
|
6
|
10
|
273.579
|
99.2 %
|
32.206
|
85.85 %
|
YES
|
Evaluated
|
3b
|
Class BLW - Fish Kill:
The Class BLW) uses are assessed (evaluated) as “partially supported” based on results of a fish kill investigation in August 2009 and another in October of 2015. Because the cause of the fish kill was not identified, or the fish kill was attributed to a non-pollutant cause (e.g., winterkill), the assessment type is “evaluated.” Segments assessed using “evaluated” assessments are placed in Category 3b and are added to the state list of waters in need of further investigation. If no additional fish kills are reported in the segment for a 10 year period, the Category will be changed from 3b to 3a (water not assessed).
Details about the 2009 and 2015 fish kills can be found here:https://programs.iowadnr.gov/fishkill/Events/888,https://programs.iowadnr.gov/fishkill/Events/821
Class HH - No Data
