Lake Orient IA 05-NOD-1396
Adair County S20T74NR31W approx 1 mi SW of Orient.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 12/30/2021 2:17:57 PM
- Updated
- 2/17/2022 11:13:39 AM
The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by poor water clarity due to non-algal turbidity and algal turbidity. Violations of the Class A1 criterion for pH also contributed to impairment at this lake. The Class BLW use was assessed (monitored) as “not supported” due to violations of the Class BLW criterion for pH. The Class BLW use was also assessed (evaluated) as “WINOFI” due to cyanobacteria algae blooms. The Class C was assessed as “fully supported.” All other designated uses were “not assessed.” Note: A TMDL for algae and pH at Orient Lake was prepared by DNR and approved by EPA in October 2020. Additionally, a TMDL for siltation at Orient Lake was prepared by DNR and approved by EPA in 2001. Because all Section 303(d) impairments are identified for the current assessment/listing cycle are addressed by the TMDL, this waterbody is placed in 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 2016-2020 22010002 Lake
Orient
Class A1 - Indicator Bacteria: No Data 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 22010002 6 15 / 5 7.8 9.4 8.6 3 4 NO Monitored Full According to DNR's methodology, a lake must meet water
quality standards for two consecutive cycles to suggest
de-listing. Therefore, Lake Orient will remain listed for the 2022
cycle as "not supported" its Class A1 use 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 22010002 6 Chlorophyll a TSI 15 / 5 36 85 68 YES Monitored Not 22010002 6 Secchi TSI 15 / 5 62 93 77 YES Monitored Not 22010002 6 Total Phosphorus TSI 15 / 5 69 108 95 NA NA NA 22010002 6 Inorganic suspended solids 15 / 5 0.7 34.3 11 NA NA NA 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 22010002 6 Ammonia 15 / 5 0.0003 0.6903 0.08 NA 0 / 0 4 NO Monitored Full 22010002 6 Dissolved Oxygen 15 / 5 2.6 14.6 8.4 1 NA / NA 4 NO Monitored Full 22010002 6 pH 15 / 5 7.8 9.4 8.6 3 NA / NA 4 NO Monitored Full 22010002 6 Temperature 15 / 5 20.1 28.2 23.9 0 NA / NA 4 NO Monitored Full According to DNR's methodology, a lake must meet water
quality standards for two consecutive cycles to suggest
de-listing. Therefore, Lake Orient will remain listed for the 2022
cycle as "not supported" its Class BLW use 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 Concentration = 75th Percentile Assessment Type Support Level 22010002 6 5 471.76 99.9% 293.56 89.8% YES Evaluated 3b Class C - Conventional 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 22010002 6 Inorganic nitrogen (nitrate and nitrite) 15 / 5 0.02 3.1 0.5 0.035 0 NO Monitored Full 22010002 6 pH 15 / 5 7.8 9.4 8.6 8.7 3 NO Monitored Full
Class HH: No Data