Hewett Creek IA 01-VOL-307
mouth (S12 T92N R6W Clayton Co.) to south line of S29 T92N R6W Clayton Co.
- Cycle
- 2020
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 8/25/2020 8:11:11 AM
- Updated
- 10/15/2020 12:06:11 PM
The presumptive Class A1 and the presumptive Class A2 uses remain 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 "partially supported" due to violations of the Class BCW1 criterion for temperature and on biological sampling data. All other designated uses were "not assessed".
Sources
of Data: 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 Presumptive Class
A1 - Indicator Bacteria: 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 Presumptive Class
A2 - Indicator Bacteria: 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 Class A - pH: 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 Class BCW1 - 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 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 Partial Class
BCW1 - Biological Sampling: 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 Overall
Assessment: Community Assessment Type Assessment Result Support Level Earned IR Category Actual IR Category Reason Benthic Macroinvertebrates Evaluated Fail (1/4) Partial 3bc 5bv Assessment
is evaluated because samples used to complete the assessment weren’t
collected in the last five years. Class
BCW1 – Trout Natural Reproduction: Based
on the January 2020 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. Class
BCW1 – Continuous Monitoring: 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. Class HH - No Data