Blue Lake IA 06-WEM-1728
Alternate name(s) for this segment: Lewis and Clark Lake
Monona County S35T84NR46W 2 mi. W of Onawa.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 10/27/2025 3:10:37 PM
- Updated
- 11/24/2025 2:16:35 PM
The Class A1 use was assessed (monitored) as “not supported” due to high levels of indicator bacteria and due to the occurrence of aesthetically objectionable conditions caused by poor water transparency related to non-algal turbidity and algal blooms. The Class BLW use was assessed (monitored) as “WINOFI.” All other designated uses were “not assessed.” Note: A TMDL for the algae and turbidity impairments at Blue Lake was prepared by DNR and approved by EPA in January 2009. Because not all Section 303(d) impairments identified for the current assessment/listing cycle (algae) are addressed by the TMDL, this waterbody was placed in IR Category 5a (impaired; TMDL needed).
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2022-2024 21670001 Blue
Lake Beach
Iowa DNR 6 WQ CY 2020-2024 22670002 Blue
Lake
Class A1 - Indicator Bacteria: Site ID Data Source ID # Samples per Year (2022/ 2023/2024) 2022 Geometric Mean 2023 Geometric Mean 2024 Geometric Mean Violates Annual Geometric Mean? # 2022 SSM violations / SSM Violations needed for impairment # 2023 SSM violations / SSM Violations needed for impairment # 2024 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 21670001 6 15/13/15 35 43 106 NO 2 / 4 2 / 4 4 / 4 YES MONITORED NOT 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 22670002 6 12 / 4 8.1325 9 8.41 0 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 22670002 6 Chlorophyll a TSI 15 / 5 57 87 68 YES MONITORED NOT 22670002 6 Secchi TSI 15 / 5 66 97 77 YES MONITORED NOT 22670002 6 Total Phosphorus TSI 15 / 5 66 92 75 NA NA NA 22670002 6 Fixed suspended solids 15 / 5 1.9 182 18.5 NA NA NA 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 22670002 6 Dissolved Oxygen 12 / 4 6.2 13.7 9.3 0 NA / NA 4 NO MONITORED FULL 22670002 6 pH 12 / 4 8.1325 9 8.41 0 NA / NA 4 NO MONITORED FULL 22670002 6 Temperature 12 / 4 17.3 29.1 24.6 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 22670002 6 6 271.1051391 66.50% 3.503031556 17.91% NO EVALUATED NA 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 22670002 6 Ammonia 12 / 4 0.276 0.09 0.08 0 / 0 NO MONITORED FULL Class BLW - Additional Information: Information from the DNR
Fisheries Bureau suggests that Blue Lake has a poor recreational fishery and a
large carp population. The Class BLW use was assessed (evaluated) as “WINOFI”
based on information from the DNR Fisheries Bureau.
Class HH - No Data