Green Valley Lake IA 05-PLA-1472
Union County S26T73NR31W 2.5 mi NW of Creston.
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2016 | Class BLW | Organic Enrichment: Low Dissolved Oxygen | Ambient monitoring: Iowa DNR-lakes | TMDL preparation and approval |
| 2004 | Class A1 | Algal Growth: Chlorophyll a | Ambient monitoring: Iowa DNR-lakes | TMDL preparation and approval |
| 2016 | Class A1 | Turbidity: Secchi Disk Transparency | Ambient monitoring: Iowa DNR-lakes | TMDL preparation and approval |
The Class A1 uses are assessed (monitored) as “not supported” due to algal and non-algal turbidity. The Class BLW uses are assessed (monitored) as "not supported" due to violations of the Class BLW criterion for DO and a large population of cyanobacteria. The Class C uses are assessed (monitored) as “fully supporting.” Class HH uses are assessed as "fully supported" based on fish tissue sampling. Note: A TMDL for algae, turbidity, and dissolved oxygen at Green Valley Lake was prepared by DNR and approved by EPA in 2019. Because all Section 303(d) impairments identified for the current assessment/listing cycle (algal growth, turbidity, and dissolved oxygen) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved).
Sources of
Data: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2016-2018 21880001 Green Valley Beach (Green Valley State
Park)
Iowa DNR 6 WQ CY 2014-2018 22880001 Green Valley Lake Lake Deep Point Iowa DNR 6 WQ CY 2014-2015 14000156 Green Valley Lake TMDL East Arm Sampling Point Iowa DNR 6 WQ CY 2014-2015 14000157 Green Valley Lake TMDL West Arm Sampling Point Iowa DNR
FT See Below 8 Green Valley Lake
Class A1 -
Indicator Bacteria: Site ID Data Source ID # Samples / # Years 2016 Geometric Mean 2017 Geometric Mean 2018 Geometric Mean Annual Geometric Mean Violation # Violations % Violations Significantly >10% Violations Assessment Type Support Level 21880001 6 32 / 3 11.73 16.8 18.91 No 3 9% NO Monitored Full 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 22880001 6 15 / 5 9.8 8.47 8.5 3 20% 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 14000156 6 Chlorophyll a TSI 27 / 2 62 107 70 YES Monitored Not 14000157 6 Chlorophyll a TSI 27 / 2 65 102 72 YES Monitored Not 22880001 6 Chlorophyll a TSI 43 / 5 36 94 68 YES Monitored Not 22880001 6 Secchi TSI 15 / 5 62 83 71 YES Monitored Not 14000156 6 Total Phosphorus TSI 27 / 2 65 121 79 NA NA NA 14000157 6 Total Phosphorus TSI 27 / 2 47 161 81 NA NA NA 22880001 6 Total Phosphorus TSI 43 / 5 63 98 81 NA NA NA 22880001 6 Inorganic suspended solids 15 / 5 1.05 13.5 5.4 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 22880001 6 Ammonia 15 / 5 0.6041 0.07 0.02 0 / 0 0% / 0% NO Monitored Full 22880001 6 Dissolved oxygen 15 / 5 15.2 7.3 6.8 NA / 5 NA / 33% YES Monitored Not 22880001 6 pH 15 / 5 9.8 8.47 8.5 3 / NA 20% / NA NO Monitored Full 22880001 6 Temperature 15 / 5 26.3 23.4 23.3 0 / 0 0% / 0% 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 Wet Mass = 75th
Percentile Assessment Type Support Level 22880001 6 11 279.933 99.7 % 64.195 96.7 % YES Evaluated 3b Class C -
Conventional Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Violations % Violations Significantly >10% Violations Assessment Type Support Level 14000156 6 Chloride 28 / 2 10 7.9 7.7 0 0% NO Monitored Full 14000157 6 Chloride 28 / 2 10 7.9 7.8 0 0% NO Monitored Full 22880001 6 Chloride 29 / 2 10 7.8 7.6 0 0% NO Monitored Full 14000156 6 Inorganic nitrogen (nitrate and nitrite) 27 / 2 2.1 0.37 0.05 0 0% NO Monitored Full 14000157 6 Inorganic nitrogen (nitrate and nitrite) 27 / 2 2.2 0.43 0.16 0 0% NO Monitored Full 22880001 6 Inorganic nitrogen (nitrate and nitrite) 43 / 5 2.2 0.35 0.05 0 0% NO Monitored Full Class HH - Fish
Tissue Sampling: Site ID Date Species Name Biopart # in sample chlordane result chlordane violation? PCBs result PCBs violation? Hg result Hg violation? Assessment Type Support Level 8 9/13/11 channel catfish fillet 3 <0.03 No <0.09 No 0.0541 No Evaluated Full 8 9/13/11 largemouth bass plug 4
0.200 No Evaluated Full
Additional Notes: A fishery renovation was completed in 2008. Watershed improvements are being installed and other a sediment removal project is scheduled for the winter of 2009/2010. Water quality improvements are expected as this project progresses and the lake is filled. Because of the water quality improvement project activities throughout the assessment period, a limited number of samples were collected in 2008-2012.