Iowa DNR
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Water Quality Assessments

Impaired Waters List

Indian Creek IA 03-SSK-943

mouth (S32 T80N R20W Jasper Co.) to confluence of East Indian and West Indian creeks in S16 T82N R22W Story Co.

Assessment Cycle
2018
Release Status
Final
Cycle Period
2014 - 2016
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
5/14/2019 11:33:49 AM
Updated
7/8/2019 3:20:38 PM
Assessment conducted in accordance with Iowa's 2018 IR methodology
Use Support
Class A1
Partially Supported
Bacteria: Indicator Bacteria- E. coli
Support Level
Partially Supported
Impairment Code
5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Iowa DNR-rivers
TMDL Priority
Tier III
Class BWW2
Partially Supported
Biological: low aquatic macroinvertebrate IBI
Support Level
Partially Supported
Impairment Code
5b-v - Biological - verified
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2016
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
TMDL Priority
Tier IV
General Use
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW2) aquatic life uses are assessed (monitored) as "partially supported" based on results of 2012, 2013 and 2016 biological sampling and on results of ambient chemical/physical water quality monitoring. The sources of data for this assessment are (1) results of DNR/SHL monthly ambient monitoring conducted from 2014 through 2016 on Indian Creek at a bridge 4.8 miles north of Colfax and 1.8 miles east of Green Castle in Jasper County (station 10500001) and (2) DNR/SHL biological sampling near Mingo and Colfax in 2012, 2013 and 2016.

Assessment Explanation

The presumptive Class A1 uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli).The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at DNR station 10500001 near Colfax were as follows: the 2014 geometric mean was 561 orgs/100 ml, the 2015 geometric mean was 585 orgs/100 ml, and the 2016 geometric mean was 570 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Nineteen of the combined 24 samples (79%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported."

Based exclusively on the results of ambient chemical/physical water quality monitoring, the Class B(WW2) aquatic life uses should be assessed (monitored) as "fully supported".Results of chemical/physical water quality monitoring at DNR station 10500001 near Colfax showno violations of Class B(WW2) water quality criteria for 36 Ammonia samples (maximum = 1.3 mg/L), 36 Dissolved Oxygen samples (minimum = 7.3 mg/L), 36 pH samples (range = 7.5 to 8.8), 36 Temperature samples (maximum = 26° c), 36 Chloride samples (maximum = 40 mg/L), or 36 Sulfate samples (maximum = 70 mg/L) occurred during monitoring from January 2014 to December 2016.Thus, these results thus suggest “full support” of the Class B(WW2) aquatic life uses.

In contrast to the assessment of aquatic life uses based on chemical/physical water qualitydata, the biological data collected in 2012, 2013 and 2016 indicate that the Class B(WW2) aquatic life uses be assessed as “partially supporting." A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2012 BMIBI score was 18 (poor), the 2013 BMIBI score was 43 (fair) and the 2016 BMIBI score was 47 (fair). No fish community sampling was conducted at the time of the benthic macroinvertebrate sampling. The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. The segment passed the BMIBI BIC 0/3 times in the last fiveyears. This assessment is considered "monitored" because there were two or more samples (BMIBI) collected in multiple years from 2012-2016.

Monitoring and Methods
Assessment Key Dates
10/1/2012 Biological Monitoring
9/25/2013 Biological Monitoring
1/15/2014 Fixed Monitoring Start Date
12/7/2016 Fixed Monitoring End Date
10/14/2016 Biological Monitoring
Methods
230 Fixed station physical/chemical (conventional plus toxic pollutants)
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
420 Water column surveys (e.g. fecal coliform)
360 HABITAT ASSESSMENT