Briggs Woods Lake IA 04-UDM-1255
Hamilton County S17T88NR25W near Webster City.
- 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 3:10:05 PM
- Updated
- 11/20/2025 8:10:10 AM
The Class A1 use was assessed (monitored) as "not supported" due to aesthetically objectionable conditions caused by non-algae turbidity and algal blooms. The Class BLW use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) use was assessed as “fully supported” based on fish tissue sampling data. Note: The DNR TMDL prepared for impairments due to algae and low dissolved oxygen (organic enrichment) was approved by U.S.EPA in July 2012. Additionally the DNR TMDL prepared for pH was approved by U.S.EPA in February 2021. Because not all the impairments identified for this lake are covered by this TMDL (Turbidity Secchi disc transparency), this lake remains in IR Category 5a.
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2020-2024 22400004 Briggs
Woods Lake
Iowa DNR 6 FT See Below 1077 Briggs
Woods Lake
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 22400004 6 18 / 5 7.53 9.37 8.6 3 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 22400004 6 Chlorophyll a TSI 18 / 5 28 85 67 YES MONITORED NOT 22400004 6 Secchi TSI 18 / 5 45 79 68 YES MONITORED NOT 22400004 6 Total Phosphorus TSI 18 / 5 49 85 65 NA NA NA 22400004 6 Fixed suspended solids 18 / 5 0.7 13 2 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 22400004 6 Dissolved Oxygen 17 / 5 5.1 17.3 9.3 0 NA / NA 4 NO MONITORED FULL 22400004 6 pH 18 / 5 7.53 9.37 8.6 3 NA / NA 4 NO MONITORED FULL 22400004 6 Temperature 18 / 5 13.6 29.8 22 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 22400004 6 8 39.8469 88.87% 10.5546 42.68% 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 22400004 6 Ammonia 18 / 5 1.46 0.17 0.03 0 / 0 NO MONITORED FULL Class HH - Fish
Tissue Sampling: Site ID Biopart Year Species # in sample / # of samples Avg Length (cm) (Avg) Hg (ppm) Chlordane (ppm) Sum PCBs (ppm) 1077 tissue plug 2019 largemouth bass 11 35.3 0.093
1077 tissue plug 2017 largemouth bass 3 40.4 0.247
Support Level Full