Three Mile Lake IA 05-GRA-1371
Union County S32 T73N R29W approximately 3 miles N or Afton.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 10/27/2025 3:10:13 PM
- Updated
- 1/2/2026 10:42:06 AM
The Class BLW use was assessed (monitored) as “fully supported.” The Class C (drinking water) use was assessed (monitored) as "fully supported” based on water quality monitoring data and drinking water compliance monitoring required by the DNR. All other designated uses are “not assessed.” Note: This lake is not designated for Class A1 (primary contact recreation) uses in the Iowa Water Quality Standards.
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2020-2024 22880003 Three
Mile Lake
Creston Water Supply 27 WQ CY 2022-2023 99990213 Three
Mile Creek Lake Public
water Supply 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 22880003 6 Dissolved Oxygen 13 / 5 4.24 9.12 7.04 1 NA / NA 4 NO MONITORED FULL 22880003 6 pH 13 / 5 7.59 9.03 8.1 1 NA / NA 4 NO MONITORED FULL 99990213 27 pH 547 / 2 7.78 8.81 8.28 0 NA / NA 65 NO MONITORED FULL 22880003 6 Temperature 13 / 5 18.3 29 23.6 0 NA / NA 4 NO MONITORED FULL 99990213 27 Temperature 547 / 2 0.55556 27.7778 11.935 0 NA / NA 65 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 22880003 6 3 27.66524543 88.90% 0.545609533 9.79% NO EVALUATED NA Class BLW - Protection of Submerged Aquatic Vegetation: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Median Value Median Value = SAV Assessment Type Support Level 22880003 6 Total suspended solids 13 / 5 2.4 18 8 NO MONITORED FULL 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 22880003 6 Ammonia 13 / 5 0.326 0.1 0.08 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 99990213 27 Fluoride 79 / 2 120 450 311 310 0 NO MONITORED FULL 22880003 6 Inorganic nitrogen (nitrate and nitrite) 12 / 5 0.03 1.53 0.43 0.18 0 NO MONITORED FULL 22880003 6 pH 13 / 5 7.59 9.03 8.1 8.03 1 NO MONITORED FULL 99990213 27 pH 547 / 2 7.78 8.81 8.28 8.28 0 NO MONITORED FULL Class C - Iowa Drinking Water Compliance Report: Compliance monitoring required by the Iowa DNR Water Supply Operations and Engineering Sections did not show violations of finished water caused by source water at the Creston Water Supply facility during the 2022-24 monitoring period. The results of compliance monitoring as reported in annual compliance reports are available at the following location at the Iowa DNR’s home page: https://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Supply-Engineering/Annual-Compliance-Report.
Class HH - No Data