Hannen Lake IA 02-IOW-704
Benton County S34T82NR11W 4 mi SW of Blairstown.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 12/21/2021 5:38:50 PM
- Updated
- 2/17/2022 9:54:55 AM
The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by algae. The level of inorganic suspended solids was relatively low and does not suggest water quality problems due to non-algal turbidity. The Class BLW use was assessed (monitored) as “not supported” due to violations of the Class BLW criterion for DO. All other designated uses were “not assessed.” NOTE: A TMDL was prepared for and approved by the U.S. EPA in 2013 for pH and algae. Because all of the impairments at this lake are addressed by the TMDL, Hannen Lake will be categorized as category 4a; water impaired but no TMDL needed for the current assessment/listing cycle.
Class A1 - Indicator Bacteria: Site ID Data Source ID # Samples per Year (2018/ 2019/2020) 2018 Geometric Mean 2019 Geometric Mean 2020 Geometric Mean Violates Annual Geometric Mean? # 2018 SSM violations / SSM Violations needed for impairment # 2019 SSM violations / SSM Violations needed for impairment # 2020 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 22060001 6 3/3/3 1 12 10 NO 0 / NA 0 / NA 0 / NA NO Evaluated Full 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 22060001 6 15 / 5 7.3 9.3 8.4 1 4 NO Monitored 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 22060001 6 Chlorophyll a TSI 15 / 5 36 82 64 NO Monitored Full 22060001 6 Secchi TSI 15 / 5 43 83 69 YES Monitored Not 22060001 6 Total Phosphorus TSI 15 / 5 33 85 74 NA NA NA 22060001 6 Inorganic suspended solids 15 / 5 0.3 8 2.5 NA NA NA Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, the Class A1 use of Hannen Lake remains listed as "not supported" due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Chlorophyll a must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Hannen Lake will remain listed as "not supported" for the 2022 assessment/listing cycle. Class BLW - Conventional 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 22060001 6 Ammonia 15 / 5 0.0003 0.609 0.1 NA 0 / 0 4 NO Monitored Full 22060001 6 Dissolved Oxygen 15 / 5 2.88 26 8.17 4 NA / NA 4 YES Monitored Not 22060001 6 pH 15 / 5 7.3 9.3 8.4 1 NA / NA 4 NO Monitored Full 22060001 6 Temperature 15 / 5 20.7 27.6 23.6 0 NA / NA 4 NO Monitored Full 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 Concentration = 75th Percentile Assessment Type Support Level 22060001 6 6 35.59 88.5% 5.56 44.5% NO Evaluated NA
Class HH: No Data