Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Iowa River IA 02-IOW-622

from south corporate limit of Wapello (S35, T74N, R3W, Louisa Co.) to Long Cr (S1, T74N, R4W, Louisa Co.)

Assessment Cycle
2016
Release Status
Final
Result Period
2012 - 2014
Created
8/25/2016 9:12:58 AM
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Last Updated
9/26/2016 9:41:37 AM
Use Support
Class A1
Recreation
Primary contact

Partially Supporting - Bacteria: Indicator Bacteria, E. coli

Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2012
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: USGS
TMDL Priority
Tier III
Class B(WW-1)
Aquatic Life
Warm Water Type 1

Partially Supporting - Biological: low aquatic macroinvertebrate IBI

Impairment Code
3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2010
Impairment Rationale
Low Biotic Index
Data Source
Beach monitoring: Iowa DNR WQMA
Class HH
Human Health

Partially Supporting - Pesticides: Dieldrin

Impairment Code
3b - Use potentially impaired based on an evaluated assessment.
Cause Magnitude
Slight
Status
Continuing
Source
Agriculture
Source Confidence
N/A
Cycle Added
2012
Impairment Rationale
Potential Impairment
Data Source
Ambient monitoring: USGS
General Use
General Use water

Not Assessed

Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 (primary contact recreation) uses are assessed as “partially supporting” (IR 5a) due to levels of indicator bacteria that slightly exceed state water quality criteria.  The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" (IR 3b-u) based on results of biological monitoring.  Results of ambient physical/chemical water quality monitoring from 2012-2014, however, suggest "full support" of the Class B(WW1) aquatic life uses.  Fish consumption (Human-Health/fish) uses are assessed (evaluated) as "partially supported" (IR 3b) due to violations of Iowa’s human-health/fish criterion for dieldrin.  Results of fish contaminant monitoring in 2007, 2008, 2010, and 2014, however, suggest low levels of common fish contaminants (mercury, PCBs, and chlordane).  Sources of data for this assessment include (1) results of ambient water quality monitoring at Wapello (USGS station 05465500) conducted from January 2012 to December 2014 as part of the USGS NAWQA program, (2) results of IDNR ambient monitoring at Wapello from January 2012 to December 2014, (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2005, 2006, 2007, 2008, 2010, and 2014, (4) results of REMAP fish contaminant monitoring in 2006, and (5) 2002, 2012 and 2013 IDNR/SHL biological sampling data.   

Assessment Explanation

The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supporting” due to levels of indicator bacteria that slightly exceed the Class A1 water quality criteria.  The geometric means of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2012 through 2014 at USGS station 05465500 at Wapello were as follows:  the 2012 geometric mean was 48 orgs/100 ml, the 2013 geometric mean was 33 orgs/100 ml, and the 2014 geometric mean was 108 orgs/100 ml.  All three geometric means are below the Class A1 criterion of 126 orgs/100 ml.  Four of the 20 samples (20%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.  According to Iowa DNR’s assessment/listing methodology, the violation frequency of Iowa’s single-sample maxiumum criterion during the 2012-2014 monitoring period is not significantly greater than 10%.  Bacteria monitoring at the IDNR ambient station at Wapello did not generate sufficient data to recreation season geometric means:  only five samples were collected over the three-year monitoring period.  These data do not meet the IDNR data quantity guidelines and thus too few data are available to calculate a meaningful geometric mean for comparison to the Class A1 criterion. 

According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if all recreation season geometric means meet the respective water quality criterion, the contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  In addition, “full support” of the Class A1 uses is indicated if the percentage of samples that exceed Iowa’s single-sample criterion of 235 orgs/100 ml is not significantly greater than 10%.  Thus, comparison of bacteria data for the 2012-2014 monitoring period to both the geometric mean criteria and the single-sample maximum criterion suggest “full support” of the Class A1 uses.  The IDNR assessment/listing methodology, however, requires that levels of indicator bacteria must show “full support” for two consecutive listing cycles (i.e., five consecutive years) before a bacteria impairment can be de-listed.  Thus, the existing IR Category 5a impairment of the Class A1 uses will remain.  Regardless of this impairment, levels of indicator bacteria in this segment of the Iowa River have historically been and continue to be very low relative to levels in other stream/river segments in Iowa. 

Regarding support of the Class B(WW1) uses, results of USGS/NAWQA monitoring and IDNR ambient monitoring from 2012 through 2014 suggest “full support” of these uses.  Result of this monitoring showed no violations of Class B(WW1) water quality criteria in the approximately 45 samples collected at the USGS station and the nine samples collected at the Iowa DNR station for the following parameters:  dissolved oxygen, ammonia-nitrogen, chloride, sulfate, and temperature.  Violations of Class B(WW1) criteria for conventional parameters occurred in the following:  one of the nine IDNR samples (11%) violated the criteria for pH; and four of 45 USGS samples (9%) violated the criteria for pH.  These monitoring results do not suggest impairment of the Class B(WW1) aquatic life uses.  According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as pH, dissolved oxygen, or temperature, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b).  According to IDNR’s assessment/listing methodology, however, the results from the USGS and IDNR monitoring stations in this river segment, however, do not indicate that significantly greater than 10% of the samples exceed the Class B(WW1) criteria for pH.  Thus, the results of chemical/physical water quality monitoring from 2012 to 2014 in this segment suggest that the Class B(WW1) aquatic life uses should be assessed (monitored) as “fully supported.” 

Results of this monitoring for toxics also suggest “full support” of the Class B(WW1) aquatic life uses.  No violations of Class B(WW1) criteria occurred for the following parameters monitored by USGS:  arsenic (44 samples), chlorpyrifos (19 samples), DDE (1 sample), dieldrin (19 samples) or selenium (44 samples).  Similar to the results of monitoring for conventional parameters, results of monitoring for toxics suggest “full support” as none of the parameter exceed their respective criteria in more than one sample over the three year period (2012-2014).   

However, the biological monitoring conducted in this segment suggests (evaluated) partial support of the aquatic life uses.  This evaluated biological assessment was based on data collected in 2002, 2012 and 2013 as part of the IDNR/SHL stream REMAP and large river benthic macroinvertebrate sampling projects.  A series of biological metrics that 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 2002 FIBI score was 40 (fair).  The 2012 and 2013 BMIBI scores were 14, 20 (both poor).  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 from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008.  The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.  This segment passed the FIBI BIC 1/1 times in 2002 and passed the BMIBI BIC 0/2 times in the last five years.  This assessment is considered evaluated because the drainage area (12490 and 12499 mi2) above the sampling sites is greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.  Even though this site passed the FIBI BIC and failed to meet the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment don’t fall in the calibrated watershed size. 

The Human Health designated use (including the fish consumption use) remains assessed (evaluated) as “partially supporting” (IR Category 3b-potentially impaired) due to levels of dieldrin in water.  For the 2012-2014 monitoring period, all 19 samples were reported by USGS as less than the level of detection of 0.008 ppb. .  For the 2010-2012 monitoring period, one of 50 samples analyzed by USGS for dieldrin during the 2010-2012 monitoring period exceeded this Class HH/fish criterion:  the sample collected on June 6, 2011, contained 0.005 ug/l of dieldrin.   For the 2008-2010 monitoring period, however, none of the 44 samples collected from 2008-2010 at USGS station 05465500 contained detectable levels of dieldrin (detection level of 0.009 ug/l), but two samples contained “estimated” levels of dieldrin (both samples were estimated to have 0.002 ug/l of dieldrin; these samples were collected on June 2, 2008 and June 25, 2009. 

According to IDNR’s assessment/listing methodology, if the average level of a toxic metal or pesticide is greater than its respective human health criterion, impairment ("nonsupport") of the Human Health use is indicated.  However, the samples with detectable levels of dieldrin at this monitoring station are too few (three over seven years of monitoring) and the method detection level (either 0.008 or 0.009 ug/l) is far too high (~16 times the HH criterion for dieldrin) to allow calculation of a meaningful summary statistic (i.e., mean) for dieldrin at this monitoring station.  Regardless, the infrequent occurrence of dieldrin in water is of concern and thus suggests that the Human Health uses should remain assessed as “potentially impaired” and included in Category 3b of Iowa’s Integrated Report.  None of the other Human Health parameters monitored for by USGS during the 2012-2014 monitoring period exceeded their respective water quality criteria:  arsenic (44 samples), DDE (1 sample), and selenium (44 samples).

Despite the occasional report of a detectable level of dieldrin, results of fish contaminant sampling in this river segment have show very low levels of this now-banned pesticide.  Levels of dieldrin in the 2007 composite sample of Common Carp fillets was 6 ppb of dieldrin.  Levels in the composite sample of whole-fish common carp analyzed for the 2008 RAFT and were 60 ppb in the composite whole-fish Common Carp sample analyzed in 2014.  Although Iowa does not have a consumption advisory trigger level for dieldrin, the levels seen in the 2007 fillet samples and the 2008 and 2014 whole-fish composite samples from Wapello are well below the Iowa’s previous advisory trigger of 300 ppb of dieldrin (i.e., the U.S.  FDA action level for dieldrin).  Levels of dieldrin in Iowa fish have declined significantly since the early and mid-1980s when levels of 300 ppb to 500 ppb were not uncommon.  Due to the low levels of dieldrin in fish tissue samples from this river segment, and due to the low frequency with which violations of the human health (fish + water) dieldrin criterion occurred (5%), this assessment is considered appropriate for Iowa’s IR Category 3b (potential impairment).  IR Category 3b waters will be added to Iowa’s list of waters in need of further investigation. 

Fish contaminant monitoring for toxic parameters other than dieldrin (e.g., mercury, PCBs, and chlordane) suggest “full support” of fish consumption uses.  Fish consumption was conducted near Wapello in (1) 2005, 2006, 2007, 2008, 2010, and 2014 as part of the EPA/IDNR fish tissue (RAFT) program and (2) 2006 as part of the IDNR REMAP project (Site 45).  This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring.  Due to a change in the design of the RAFT program, this site was sampled in the consecutive years of 2005 and 2006.  The 2008 composite whole-fish samples of common carp contained the following levels of common contaminants:  mercury: 0.135 ppm; total PCBs: 0.217 ppm; and technical chlordane: 0.067 ppm.  Contaminant levels in the 2010 composite whole-fish sample of common carp had similar levels: mercury: 0.061 ppm; total PCBs: 0.111 ppm; and technical chlordane: 0.091 ppm.  The 2014 whole-fish Common Carp sample had similar levels of these contaminants:  mercury 0.11 ppm; total PCBs:  <0.24 ppm, and chlordane:  0.12 ppm.  These results do not suggest the need for issuance of a consumption advisory. 

Due, however, to the low frequency with which violations of the human health (fish + water) dieldrin criterion occurs, the assessment of the HH-fish consumption uses in this river segment is considered appropriate for Iowa’s IR Category 3b (potential impairment).  IR Category 3b waters are added to Iowa’s list of waters in need of further investigation.

Monitoring and Methods
Assessment Key Dates
8/13/2007 Fish Tissue Monitoring
9/23/2008 Fish Tissue Monitoring
9/8/2014 Fish Tissue Monitoring
2/5/2008 Fixed Monitoring Start Date
12/1/2010 Fixed Monitoring End Date
1/5/2010 Fixed Monitoring Start Date
12/10/2012 Fixed Monitoring End Date
1/11/2012 Fixed Monitoring Start Date
12/11/2014 Fixed Monitoring End Date
9/26/2002 Biological Monitoring
10/8/2012 Biological Monitoring
10/8/2013 Biological Monitoring
9/17/2010 Fish Tissue Monitoring
Methods
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
230 Fixed station physical/chemical (conventional plus toxic pollutants)
260 Fish tissue analysis
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
330 Fish surveys
380 Quan. measurements of instream parms-- channel morphology-- floodplain-- 1-2 seasons-- by prof
420 Water column surveys (e.g. fecal coliform)