Hewett Creek IA 01-VOL-307
mouth (S12 T92N R6W Clayton Co.) to south line of S29 T92N R6W Clayton Co.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 12/15/2021 11:19:54 AM
- Updated
- 2/14/2022 7:11:28 AM
The presumptive Class A1 and the Class A2 uses were assessed as “not supported” due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BCW1 use was assessed as "not supported" due to violations of the Class BCW1 criterion for temperature and on biological sampling data. All other designated uses were "not assessed."
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 BIO See Below 435 Hewett Creek Volga – REMAP #133 Iowa DNR 6 WQ CY2012-2014 15220013 Hewett Creek at
Crystal Road HEW20 Site
ID Data
Source ID #
Samples / # Years 2012
Geometric Mean 2013
Geometric Mean 2014
Geometric Mean Annual
Geometric Mean Violation #
Violations %
Violations Significantly
>10% Violations Assessment
Type Support
Level 15220013 6 24
/ 3 655 1569 544 Yes 17 71% Yes Evaluated Not Site ID Data Source ID # Samples / #
Years 2012 Geometric
Mean 2013 Geometric
Mean 2014 Geometric
Mean Annual Geometric
Mean Violation # Violations % Violations Significantly
>10% Violations Assessment Type Support Level 15220013 6 24 / 3 655 1569 544 Yes 5 21% Yes Evaluated Not Site ID Data Source ID # Samples / #
Years Maximum Value Mean Value Median Value # Violations % Violations Significantly
>10% Violations Assessment Type Support Level 15220013 6 24 / 3 8.8 8.38 8.32 0 0% No Evaluated Full 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 15220013 6 Ammonia 16 / 2 0.11 0.06 0.05 0 / 0 0% / 0% No Evaluated Full 15220013 6 Chloride 16 / 2 33 31 31 0 / 0 0% / 0% No Evaluated Full 15220013 6 Dissolved Oxygen 23 / 3 12 9.1 9 0 / 2 0% / 9% No Evaluated Full 15220013 6 pH 24 / 3 8.8 8.38 8.32 0 / 0 0% / 0% No Evaluated Full 15220013 6 Temperature 24 / 3 24.2 14.4 14.5 NA / 5 NA / 21% Yes Evaluated Not Benthic
Macroinvertebrates: BioNet Site ID Date Drainage Area
(mi2) Ecoregion Major Drainage/
Thermal BM Sample Gear CBI score CBI Class CBI BIT CBI Pass/ Fail 435 9/15/14 8 52b MS/CW Hess 55 NA 60 Fail 435 8/4/14 8 52b MS/CW Hess 53 NA 60 Fail 435 9/9/13 8 52b MS/CW Hess 66 NA 60 Pass 435 8/14/13 8 52b MS/CW Hess 53 NA 60 Fail Community Assessment Type Assessment Result Support Level IR Category Reason Benthic
Macroinvertebrates Evaluated Fail (1/4) Not 5bv Assessment was
evaluated because samples used to complete the assessment weren’t collected
in the last five years. Based
on the January 2021 trout reproduction in Iowa streams summary prepared by the
DNR Fisheries Bureau, the Class BCW1 coldwater aquatic life use of Hewett Creek
should be assessed as "fully supported." .According to the updated
summary, this stream was placed in both Category I: streams that exhibit
consistent natural reproduction and maintain a wild population of one or more
trout species without any stocking. Additional
continuous monitoring data collected in 2013 and 2014 for the DNR/SHL coldwater
stream sampling project were examined for DO and stream temperature criteria
violations. The lowest DO concentration recorded in 126 days of continuous
monitoring was 6.7 mg/L. The daily DO minimum concentration failed to meet the
24-hour DO criterion (5 mg/L) and the 16-hour DO criterion (7 mg/L) in 0 of 126
days each. The percentage exceeding the 24-hour and 16-hour criteria (0% for
each) was less than (passing) the 10% impairment threshold used to assess
conventional water quality parameters. The associated statistical analysis
confidence level result was high (>90%). The maximum stream temperature
recorded during the sensor deployment period was 23.8 degrees (C). The BCW1
temperature criterion of 20 (C) was exceeded in 40 of 126 days. The percentage
exceeding (31.7%) was greater than (failing) the 10% impairment threshold with
high statistical confidence (>90%). Based on these data, the BCW1 aquatic
life use was assessed as impaired due to elevated stream temperature levels.
This assessment agreed with the temperature assessment completed using grab
water sampling data from watershed project monitoring in 2012-2014, which also
indicated a thermal impairment.
Presumptive Class A1 - Indicator Bacteria:
Class A2 - Indicator Bacteria:
Class A - pH:
Class BCW1 - Conventional Parameters:
Class BCW1 - Biological Sampling:
Overall Assessment:
Class BCW1 – Trout Natural Reproduction:
Class BCW1 – Continuous Monitoring:
Class HH - No Data