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
2010
Result Period
2006 - 2008
Designations
Class A1 Class B(WW-2)
Assessment Methodology
Assessment Type
Monitored
Integrated Report
Category 5p
Legacy ADBCode
IA 03-SSK-0040_0
Overall Use Support
Not supporting
Aquatic Life Use Support
Fully
Primary Contact Recreation
Not supporting
Documentation
Assessment Comments

Assessment is based on: (1) results of IDNR/UHL monthly ambient monitoring conducted from 2006 through 2008 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) IDNR/UHL biological (REMAP) monitoring near Mingo in 2003.

Basis for Assessment

Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses.   The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses).   Thus, for the current (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to levels of indicator bacteria that violate state water quality criteria.   The Class B(WW2) aquatic life uses are assessed (evaluated) as "fully supported" based on results of ambient chemical/physical water quality monitoring and on results of biological monitoring results from a 2003 REMAP site.   The sources of data for this assessment are (1) results of IDNR/UHL monthly ambient monitoring conducted from 2006 through 2008 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) IDNR/UHL biological (REMAP) monitoring near Mingo in 2003.  

EXPLANATION:  The presumptive Class A1 uses are assessed (monitored) as "not supported" based on results of ambient monitoring for indicator bacteria (E.  coli).   The geometric mean level of indicator bacteria (E.  coli) in the 21 samples collected (340 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Ten of the 21 samples (48%) exceed Iowa’s single-sample maximum value of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E.  coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "not supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).  

The Class B(WW2) aquatic life uses are assessed as "fully supported" based on results of ambient chemical, physical, and biological water quality monitoring.   Results of chemical/physical monitoring at the IDNR/UHL station show no violations of Class B(WW2) criteria for dissolved oxygen, pH, or ammonia nitrogen (maximum value = 0.35 mg/l) in the approximately 30 samples analyzed during the 2006-2008 assessment period, neither of the two samples analyzed violated the respective Class B(WW2) chronic criteria for toxic metals.   This assessment is consistent with the assessment developed for this assessment segment for previous Section 305(b) reporting cycles.  

Additionally, the aquatic life assessment remains based on biological data collected in 2003 as part of the IDNR/UHL stream REMAP project.   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 2003 FIBI score was 30 (fair) and the BMIBI score was 57 (good).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), 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 1994-2004.   The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.   The assessment is considered FS-evaluated because both the FIBI and BMIBI scores met the respective BICs with the use of the UAVs (used on single samples): FIBI = 7 points and BMIBI = 8 points.

This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years from 2004-2008.   Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).

Monitoring and Methods
Assessment Key Dates
12/2/2008 Fixed Monitoring End Date
1/11/2006 Fixed Monitoring Start Date
9/30/2003 Biological Monitoring
Methods
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
315 Regional reference site approach
330 Fish surveys
380 Quan. measurements of instream parms-- channel morphology-- floodplain-- 1-2 seasons-- by prof
230 Fixed station physical/chemical (conventional plus toxic pollutants)
420 Water column surveys (e.g. fecal coliform)
320 Benthic macroinvertebrate surveys
Monitoring Levels
Biological 4
Habitat 4
Physical Chemistry 3
Toxic 3
Pathogen Indicators 3
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 0
BioIntegrity N/A
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude
Pathogens Primary Contact Recreation Slight
  • Source Unknown
  • High