Black Hawk Lake IA 04-RAC-1134
Sac County S35T87NR36W at Lake View.
The Class A1 uses are assessed (monitored) as “partially supporting” due to violations of the state water quality criteria for indicator bacteria, poor water clarity caused by algal and non-algal turbidity. The Class BLW uses are assessed (monitored) as “fully supported.” Class HH uses are assessed as “fully supported” based on fish tissue sampling. Note: The TMDL prepared by Iowa DNR for impairments due to algae and turbidity was approved by U.S.EPA in February 2012. Not all Section 303(d) impairments identified for the current assessment/listing cycle (indicator bacteria), however, are addressed in the TMDL. Thus, this waterbody remains in IR Category 5a (impaired; TMDL required) for this assessment/listing cycle.
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 21810001 Denison Beach (Black Hawk State Park)
Iowa DNR 6 WQ CY 2016-2018 21810002 Black Hawk Campground Beach (Black Hawk
St. Park)
Iowa DNR 6 WQ CY 2014-2018 22810002 Black Hawk Lake Lake Deep Point Iowa DNR 6 WQ CY 2014-2017 22810003 Black Hawk Lake West Arm TMDL Sampling Point Iowa DNR
FT See Below 138 Black Hawk 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 21810001 6 46 / 3 114.31 80.02 126.08 Yes 13 28% YES Monitored Partial 21810002 6 44 / 3 30.41 31.53 29.59 No 3 7% 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 22810002 6 15 / 5 9.2 8.5 8.4 2 13% 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 22810002 6 Chlorophyll a TSI 54 / 5 15 80 66 YES Monitored Not 22810003 6 Chlorophyll a TSI 11 / 4 31 78 64 NO Monitored Full 22810002 6 Secchi TSI 15 / 5 47 77 65 YES Monitored Not 22810002 6 Total Phosphorus TSI 54 / 5 47 105 76 NA NA NA 22810003 6 Total Phosphorus TSI 11 / 4 53 89 80 NA NA NA 22810002 6 Inorganic suspended solids 15 / 5 0.3 12.6 3.3 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 22810002 6 Ammonia 15 / 5 0.311 0.06 0.04 0 / 0 0% / 0% NO Monitored Full 22810002 6 Dissolved oxygen 15 / 5 13.8 9.4 10.3 NA / 1 NA / 7% NO Monitored Full 22810002 6 pH 15 / 5 9.2 8.5 8.4 2 / NA 13% / NA NO Monitored Full 22810002 6 Temperature 15 / 5 27.1 22.4 23.9 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 22810002 6 11 90.528 100 % 1.404 6.4 % NO Evaluated NA 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 138 8/26/15 channel catfish fillet 5 <0.02 No <0.06 No 0.04 No Monitored Full 138 8/26/15 walleye plug 5
0.190 No Monitored Full Note: A fishery renovation and lake drawdown was completed in 2012 to remove rough fish from Black Hawk Lake.