Green Valley Lake IA 05-PLA-1472
Union County S26T73NR31W 2.5 mi NW of Creston.
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2024 | Class BLW | pH | TMDL monitoring: Iowa DNR | TMDL preparation and approval |
| 2024 | Class C | pH | TMDL monitoring: Iowa DNR | TMDL preparation and approval |
| 2024 | Class A1 | pH | TMDL monitoring: Iowa DNR | TMDL preparation and approval |
The Class A1 use was assessed (monitored) as “not supported” due to algal blooms, non-algal turbidity and violations of the Class A1 criterion for pH. The Class BLW use was assessed (monitored) as "not supported" due to violations of the Class BLW criterion for pH and "WINOFI" due to a large population of cyanobacteria. The Class C use was assessed (monitored) as “not supported” due to violations of the Class BLW criterion for pH. All other designated uses are “not assessed.” Note: A TMDL for algae, turbidity, and dissolved oxygen at Green Valley Lake was prepared by DNR and approved by EPA in 2019. Additionally, a TMDL addendum for pH at Green Valley Lake was prepared by DNR and approved by EPA in 2025. Because all Section 303(d) impairments identified for the current assessment/listing cycle are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved).
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2022-2024 21880001 Green
Valley Beach
Iowa DNR 6 WQ CY 2020-2024 22880001 Green
Valley 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 21880001 6 15/14/15 26 19 16 NO 2 / 4 0 / 4 0 / 4 NO MONITORED 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 22880001 6 15 / 5 7.4 9.7 8.5 6 4 YES MONITORED NOT 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 22880001 6 Chlorophyll a TSI 15 / 5 56 82 71 YES MONITORED NOT 22880001 6 Secchi TSI 15 / 5 56 79 72 YES MONITORED NOT 22880001 6 Total Phosphorus TSI 15 / 5 63 86 73 NA NA NA 22880001 6 Fixed suspended solids 15 / 5 0.7 26 6 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 22880001 6 Dissolved Oxygen 15 / 5 3.1 12.9 7.5 2 NA / NA 4 NO MONITORED FULL 22880001 6 pH 15 / 5 7.4 9.7 8.5 6 NA / NA 4 YES MONITORED NOT 22880001 6 Temperature 15 / 5 17.6 27.4 23.8 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 22880001 6 5 26.27724849 90.71% 19.15001761 69.59% YES EVALUATED WINOFI 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 22880001 6 Ammonia 15 / 5 0.717 0.11 0.04 0 / 0 NO MONITORED FULL Class C - Binomial Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Mean Value Median Value # Violations Violates Significantly >10% Rule? Assessment Type Support Level 22880001 6 Inorganic nitrogen (nitrate and nitrite) 14 / 5 0.03 1.38 0.38 0.15 0 NO MONITORED FULL 22880001 6 pH 15 / 5 7.4 9.7 8.5 8.3 6 YES MONITORED NOT
Class HH - No Data