Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Iowa River IA 02-IOW-628

from Burlington St. dam in Iowa City (Johnson Co.) to Coralville Reservoir dam (Johnson Co.)

Assessment Cycle
2008
Result Period
2004 - 2006
Designations
Class C Class A1 Class B(WW-1) Class HH
Assessment Methodology
Assessment Type
Evaluated
Integrated Report
Category 2b
Legacy ADBCode
IA 02-IOW-0030_2
Overall Use Support
Partial
Aquatic Life Use Support
Partial
Fish Consumption
Fully
Primary Contact Recreation
Fully
Drinking Water
Fully
Documentation
Assessment Comments

Assessment is based on results of (1) routine water quality & fish tissue monitoring as part of the UI/ACOE Coralville Water Quality Study from 2004-06, (2) IDNR/UHL ambient water quality monitoring upstream from Iowa City from 2004-06, (3) statewide assessment of freshwater mussels in 1998-99, (4) freshwater mussel surveys coordinated by the IDNR Fisheries Bureau in 2004, (5) U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2006 at Iowa City, (6) fish contaminant monitoring conducted in 2006 as part of the REMAP program (Site 302), (7) IDNR/UHL TMDL and REMAP biological monitoring conducted at four sites in 2005, (8) fish contaminant monitoring conducted in 2006 as part of the REMAP program, and (9) results of fish kill investigations in 2006 and 2007.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported" based on results of ambient monitoring for indicator bacteria upstream from Iowa City.   The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" based on fish kill investigations on April 13, 2006 and March 17, 2007.   However, results of 2004 survey of freshwater mussels that showed significant recovery of the mussel community in this segment of the Iowa River and ambient water quality monitoring suggests "full support" of the Class B(WW1) uses.   The Class C (drinking water) uses remain assessed (monitored) as "fully supported" based on results of ambient monitoring conducted by both IDNR/UHL and Corps of Engineers.   Fish consumption uses remain assessed as "fully supported" based on results of annual fish contaminant monitoring conducted (1) by the University of Iowa/Corps of Engineers in 2005 and 2006, (2) as part of the 2006 U.S.  EPA/IDNR fish contaminant (RAFT) monitoring program and (3) as part of the IDNR REMAP program in 2006.   The sources of data for this assessment include (1) results of water quality and fish tissue monitoring conducted from 2004-2006 near the Iowa City water treatment plant part of the ACOE-sponsored Coralville Reservoir Water Quality Study, (2) results of a statewide assessment of freshwater mussels in 1998-1999 conducted by Iowa State University (Arbuckle at al.  2000), (3) results of mussel surveys in 2004 coordinated by the IDNR Fisheries Bureau, (4) results of monitoring from the IDNR/UHL ambient city monitoring station upstream from Iowa City at the Dubuque Street bridge from 2004-2006, (5) results of IDNR/UHL TMDL-related monitoring at the following five stations:  below Coralville Dam (11520001), above Burlington Street Dam (11520002), near Iowa City/Site 77 (11520003), near Iowa City/Site 79 (11520004), and in Iowa City /Site 81 (11520005); (6) results of the U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2006 at Iowa City, (7) results of fish contaminant monitoring conducted in 2006 as part of the REMAP program (Site 302), (8) IDNR/UHL TMDL and REMAP biological monitoring conducted at four sites in 2005, and (9) results of fish kill investigations conducted on April 13, 2006 and March 17, 2007.

EXPLANATION:  Results of water quality monitoring at both the ACOE long-term station near the University of Iowa water treatment plant and the IDNR/UHL station upstream from Iowa City at the Dubuque Street bridge suggest that the Class A1 uses should be assessed (monitored) as "fully supported."  Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, E.  coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.  

The geometric mean level of indicator bacteria (E.  coli) in the 18 samples collected as part of UI/ACOE monitoring during recreational seasons of 2004 through 2006 (118 orgs/100ml) is below the Iowa Class A water quality criterion of 126 orgs/100ml.   Two of the 18 samples (11%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if levels of E.  coli exceed the single-sample maximum criterion in more than 10% of the samples, the primary contact recreation uses should be assessed as “partially supported.”  According to IDNR’s assessment/listing methodology, however, these results show that (1) the geometric mean meets the Class A1 criterion of 126 orgs/100 ml and (2) the violation frequency of Iowa’s single-sample maximum criterion is not significantly greater than 10%.   Thus these results do not suggest impairment of the Class A1 uses of this river segment.  

Similarly results of IDNR's ambient city monitoring for indicator bacteria upstream from Iowa City also suggest “full support” of primary contact recreation uses.   Twenty-five samples were collected upstream from Iowa City at the IDNR/UHL station at Dubuque Street during recreational seasons of 2004 through 2006.   The geometric mean of these 25 samples was only 25 E.  coli orgs/100 ml, well-below the Iowa criterion of 126 orgs/100 ml.   Only one of the 25 samples had levels of E.  coli that exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   sample maximum criterion.   According to U.S.  EPA guidelines for Section 305(b) reporting, and according to IDNR’s assessment/listing methodology, these results suggest “full support” of the Class A1 uses of this river segment.  

A comparison of monitoring results from the 2002-04 to the 2004-06 assessment periods suggests that levels of indicator bacteria in this segment of the Iowa River are very low and stable.   At the ACOE stations, the geometric means of the 18 samples collected in 2002-04 versus 2004-06 periods were 117 versus 118 orgs/100 ml, respectively.   At the IDNR (Dubuque Street) station, the geometric means for these two periods were 34 and 25 orgs/100 ml, respectively.   The generally low levels of indicator bacteria in this assessment segment are consistent with monitoring results at other stations located immediately downriver from Iowa’s federal flood control reservoirs.   Typically, these stations show the lowest levels of indicator bacteria of any river monitoring stations in the state.   The somewhat higher levels of bacteria at the downriver (ACOE) monitoring station (approximately 10 miles downriver from Coralville Dam) likely reflect inputs of indicator bacteria from (1) the Iowa River tributaries between these two stations (e.g., Muddy Creek and Clear Creek) and/or (2) the Iowa City/Coralville urban area.  

The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" based on fish kill investigations on April 13, 2006 and March 17, 2007.  Both kills involved only gizzard shad and were attributed to natural causes (temperature fluctuation).   Waters affected by such kills are appropriate for Category 2b of Iowa's Integrated Report and will thus be added to Iowa's list of waters in need of further investigation.   Despite the occurrence of these fish kills, the remainder of the various types of water quality monitoring conducted in this river segment suggest "full support" of the Class B(WW1) (aquatic life) uses.   Results of ambient chemical/physical water quality monitoring at the IDNR/UHL (Dubuque Street) and UI/ACOE (UI Water Plant) stations suggest “full support" of the Class B(WW1) aquatic life uses.   Monitoring at these stations showed no violations of Class B(WW1) criteria for ammonia-nitrogen, and only one violation for dissolved oxygen and pH, in the combined 103 samples collected at both stations during the 2004-2006 assessment period.   According to U.S.  EPA guidelines (U.S.  EPA 1997b, page 3-17), a violation frequency of less than 10% for conventional parameters such as dissolved oxygen nonetheless suggests "full support" of aquatic life uses.   Thus, the percentage of violations of the dissolved oxygen criterion at the ACOE station (1%) does not suggest an impairment of aquatic life uses in this stream segment.

Results of IDNR/UHL TMDL-related monitoring conducted in this assessment segment from March though September 2005 also suggest “full support” of the Class B(WW1) aquatic life uses.   Relatively few samples were collected at these sites:  station 11520001 below Coralville Dam:  six samples; station 11520002 above Burlington Street Dam:  four samples; station 11520003 near Iowa City/Site 77:  two samples; station 11520004 near Iowa City/Site 79:  two samples, and station 11520005 in Iowa City /Site 81:  two samples.   Based on evaluation of data for dissolved oxygen, pH, and ammonia, the only violation of a Class B(WW1) criterion in the combined 16 samples from these five stations was for dissolved oxygen in the sample collected at station 11520001 (below Coralville Dam) on August 29, 2005:  the level in the sample (4.7 mg/l) violated the criterion of 5.0 mg/l/  Thus, these results are consistent with those from the routine ambient stations monitoring by IDNR/UHL and by ACOE that show “full support” of the Class B(WW1) aquatic life uses.  

Results of recent surveys of freshwater mussels in this river segment also suggest "full support" of the Class B(WW1) aquatic life uses.   For the previous (2004) reporting cycle, these aquatic life uses were assessed (monitored) as "partially supported" based on results of the 1998-99 statewide survey of freshwater mussels.   Despite the indications of good water chemical/physical water quality in this segment, results from the 1998-99 statewide assessment of freshwater mussels in Iowa streams had suggested a potential impairment to the aquatic life uses of this stream segment.   More recent monitoring, however, suggests improvement in the status of the mussel community in this segment of the Iowa River, thus suggesting that the impairment based on the 1998-99 survey should be removed.   The rationale for this assessment is as follows.  

As part of a study to reintroduce the endangered Higgins eye mussel into the Iowa, Cedar, and Wapsipinicon rivers in eastern Iowa, a four-day mussel search was conducted in August 2004.   This survey was coordinated by staff of the IDNR Fisheries Bureau from the Guttenberg and Solon fish management stations.   The purpose of the survey was to search for transformed Higgins eye mussels growing in the substrate.   In addition to staff from the Guttenberg and Solon stations, staff from IDNR Fisheries offices in Bellevue, Rathbun, and Manchester also assisted in the effort.   Also, volunteers, county conservation boards and three divers from the U.S.  Fish and Wildlife Service assisted in the effort.   The following is an excerpt from a summary of this study:  

“In total, 54 river stretches were searched by diving, wading, sieving and basket trawling.   Nearly 2,400 mussels were collected of 27 species from the three rivers.   Particularly impressive was the apparent rebound of the mussel community in the Iowa River at Iowa City.   In that reach, 24 species of mussels were collected including some of Iowa's rarer species, the yellow sandshell (Lampsilis teres) and the buckhorn (Tritogonia verrucosa).   This may be the last substantial pistolgrip population left in the state of Iowa.”  

The 1984 mussel survey of freshwater mussels included six sample sites in this stream segment.   The species richness at these six sites was 5, 5, 13, 10, 7, and 12.   In the 1998-99 survey, the corresponding species richness values were 0, 7, 1, 2, 5, and 3, respectively.   A comparison of these two surveys showed an average percent change of minus 56% and thus suggested an impairment of the Class B(WW) aquatic life uses (for more information, see the assessment developed for the 2004 reporting cycle).   Results of the August 2004 survey, however, suggest improved richness of mussel species that likely exceeds that found during the 1984 survey.   Thus, based on this information, the mussel-related impairment of the aquatic life uses of this segment of the Iowa River was removed for the 2006 reporting/listing cycle.

Somewhat contradictory to the WQ sampling and mussel results, the fish and benthic macroinvertebrate results from this segment suggest (evaluated) "partial support" of aquatic life uses.   However, because this segment is almost completely impounded and the drainage areas above the sampling sites are much higher than the IDNR wadeable IBI calibration, the 2008 aquatic life assessment for this segment will rely on the WQ and mussel data and this biological data will be considered strictly supplemental.

This evaluated biological assessment was based on data collected in 2005 as part of the DNR/UHL stream REMAP and TMDL 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 2005 FIBI scores (n=7) ranged from 6 to 22 and the FIBI average was 11 (poor).   The 2005 BMIBI scores (n=13) ranged from 16 to 46 and the BMIBI average was 32 (fair).   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 data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.   This assessment is considered evaluated because the drainage area (average = 3188 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site failed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.

The Class C drinking water uses are assessed (monitored) as "fully supported."  Results of monitoring at the IDNR/UHL station upstream from Iowa City at Dubuque Street show one violation of the atrazine MCL in the 35 samples collected and six violations of the nitrate MCL in the 36 samples collected and analyzed over the 2004-06 period.   Maximum, mean, and median levels for atrazine at this station were 6.3, 0.4, and 0.07 ug/l; 3% of the samples exceeded the atrazine MCL.   The maximum, mean and median levels for nitrate were 12.0, 5.7, and 5.8 mg/l; 17% of the samples exceeded the nitrate MCL.   Based on IDNR’s assessment and listing methodology, these violations of Iowa’s Class C criteria do not suggest impairment of drinking water uses for this river segment.   According to this methodology, if average levels of atrazine are less than the MCL, drinking water uses should be assessed as “fully supported”.   Similarly, if less than 10% of samples violate the nitrate MCL, drinking water uses should be assessed as “fully supported”.   And, based on IDNR’s assessment methodology, these results do not suggest that significantly more than 10 percent of the samples exceed the nitrate MCL and thus do not suggest an impairment of the Class C uses of this river segment.  

Nine of the of 67 samples (13%) collected at the ACOE station near the Iowa City water treatment plant exceeded the 10 mg/l MCL for nitrate (maximum concentration = 13.6 mg/l) (atrazine is not monitored as part of the UI/ACOE program).   The average nitrate level was 6.0 mg/l; the median level was 6.1 mg/l.   Similar to the results for the IDNR/UHL ambient station at Dubuque Street, IDNR’s assessment methodology shows that these results do not indicate that significantly more than 10 percent of the samples exceed the nitrate MCL.  

Fish consumption uses remain assessed (monitored) as "fully supporting."  The results from the UI/ACOE fish contaminant monitoring in 2005 and 2006 show that levels of organochlorine contaminant are very low.   Samples were collected on the Iowa River near the Iowa River Power Dam (Coralville) and at the Iowa City Park.   The duplicate composite whole-fish samples of common carp from this segment of the Iowa River in 2005 and 2006 had low levels of chlordane measured as the sum of cis-chlordane, trans-chlordane, cis-nonachlor, trans-nonachlor, and oxychlordane.   The average level of chlordane in the two composite samples collected in 2005 was 0.023 ppm and was 0.010 ppm in the 2006 samples.   The UI/ACOE fish contaminant monitoring protocol does not include analysis for either mercury or PCBs.  

Results from the U.S.  EPA/IDNR RAFT program also suggest “full support” of the fish consumption uses in this river segment.   The results from RAFT monitoring at Iowa City in 2006 show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite sample of common carp fillets:  mercury:  0.195 ppm; total PCBs:  0.09 ppm; and technical chlordane:  0.021 ppm.  

Similarly, results from the 2006 REMAP fish contaminant monitoring show low levels of the primary contaminants in the composite sample of common carp fillets:  mercury:  0.181 ppm; total PCBs:  0.09 ppm; and technical chlordane:  <0.03 ppm.  

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.   This scenario, however, does not apply to the fish contaminant data generated by either the UI/ACOE monitoring program or the RAFT program for this river segment in 2005 and 2006.:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.

Monitoring and Methods
Assessment Key Dates
3/17/2007 Fishkill
12/6/2006 Fixed Monitoring End Date
10/23/2006 Fish Tissue Monitoring
7/12/2006 Fish Tissue Monitoring
6/22/2006 Fish Tissue Monitoring
4/13/2006 Fishkill
10/29/2005 Fish Tissue Monitoring
9/22/2005 Biological Monitoring
9/21/2005 Biological Monitoring
9/20/2005 Fixed Monitoring Start Date
8/9/2005 Biological Monitoring
8/8/2005 Biological Monitoring
8/1/2004 Biological Monitoring
1/13/2004 Fixed Monitoring Start Date
1/1/1998 Biological Monitoring
Methods
420 Water column surveys (e.g. fecal coliform)
120 Surveys of fish and game biologists/other professionals
230 Fixed station physical/chemical (conventional plus toxic pollutants)
260 Fish tissue analysis
320 Benthic macroinvertebrate surveys
220 Non-fixed station physical/chemical monitoring (conventional pollutant only)
315 Regional reference site approach
330 Fish surveys
140 Incidence of spills and/or fish kills
Monitoring Levels
Biological 4
Habitat 0
Physical Chemistry 3
Toxic 3
Pathogen Indicators 3
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 10
BioIntegrity Fair
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude
Nutrients Aquatic Life Support Not Impairing
  • Agriculture
  • Natural Sources
  • Not Impairing
  • Not Impairing
Nitrate Drinking Water Not Impairing
  • Agriculture
  • Natural Sources
  • Not Impairing
  • Not Impairing
Siltation Aquatic Life Support Not Impairing
  • Agriculture
  • Natural Sources
  • Not Impairing
  • Not Impairing
Flow alteration Aquatic Life Support Not Impairing
  • Hydromodification
  • Not Impairing
Other habitat alterations Aquatic Life Support Not Impairing
  • Habitat Modification (other than Hydromodification)
  • Not Impairing