Iowa DNR

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
Release Status
Result Period
2002 - 2004
Class A Class B(WW)
Assessment Type
Integrated Report
Category 2a
Legacy ADBCode
IA 02-IOW-0010_2
Overall Use Support
Aquatic Life Use Support
Fish Consumption
Primary Contact Recreation
Not assessed
Assessment Comments

Assessment is based on results of (1) 2002 biological (REMAP) data, (2) USGS/NAWQA ambient monitoring at Wapello from 2002-04, and (3) U.S. EPA/IDNR fish tissue (RAFT) monitoring near Wapello in 2001 and 2003.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses are not assessed due to the lack of information on levels of indicator bacteria upon which to base an assessment.   The Class B(WW) aquatic life uses are assessed (evaluated) as "fully supported" based on results of biological (fish)monitoring conducted in 2002.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2003.   Sources of data for this assessment include (1) results of ambient water quality monitoring at Wapello conducted from January 2002 to September 2004 as part of the USGS NAWQA program, (2) results of biological monitoring conducted in 2002 as part of the IDNR/UHL REMAP project, and (3) results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Wapello in 2003.  

EXPLANATION:  The Class A (primary contact recreation) uses remain “not assessed” due to lack of data on indicator bacteria upon which to base an assessments.   The monitoring conducted on the Iowa River at Wapello from 2002 through 2004 by USGS (station 05465500) did not include analysis for indicator bacteria.   Thus, due to this lack of information, an assessment of support of the Class A uses was not developed.  

Regarding support of the Class B(WW) uses, results of the USGS/NAWQA monitoring from January 2002 through September 2004 showed (1) no violations of Class B(WW) water quality criteria for dissolved oxygen (29 samples) or ammonia-nitrogen (26 samples) and (2) no violations of the Class B(WW) chronic water quality criteria for chlorpyrifos, DDE, or dieldrin in the 24 samples analyzed.   Note:  the assessment of aquatic life uses developed for the 2000 report ("partially supported”) was based on two violations of the Class B(WW) chronic WQ criterion for dieldrin in the 52 samples collected between March 1996 and August 1998.   Because no dieldrin was detected in the 34 samples collected between October 1998 and September 2001, this assessment was changed to "fully supported" for the 2002 report.   USGS monitoring conducted from September 2001 through September 2004 have shown no levels of dieldrin above the level of detection (0.005 ug/l) thus confirming the lack of violations of dieldrin criteria in this river reach.

SUMMARY:  This evaluated biological assessment was based on data collected in 2002 as part of the DNR/UHL stream REMAP project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria 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 39 (fair).   The aquatic life use support was assessed (evaluated) as Fully Supporting (=FS), based on a comparison of the FIBI score 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.   This assessment is considered evaluated because the drainage area (12500 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 passed the FIBI BIC, 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.

Fish consumption uses are assessed (monitored) as "fully supported" based on the 2003 EPA/IDNR fish tissue (RAFT) sampling on the Iowa River at Wapello.   This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring.   The results from the 2003 sampling show that levels of the primary contaminants (chlordane, PCBs and mercury) are well below levels of concern.   The composite whole-fish samples of common carp had low levels of the primary contaminants:  mercury: 0.103 ppm; total PCBs: 0.148 ppm; and technical chlordane: 0.073 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 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 from the 2003 RAFT sampling conducted in this assessment segment:  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
9/8/2004 Fixed Monitoring End Date
8/7/2003 Fish Tissue Monitoring
9/24/2002 Biological Monitoring
1/9/2002 Fixed Monitoring Start Date
9/5/2001 Fish Tissue Monitoring
8/20/1999 Fish Tissue Monitoring
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
260 Fish tissue analysis
230 Fixed station physical/chemical (conventional plus toxic pollutants)
Monitoring Levels
Biological 3
Habitat 0
Physical Chemistry 3
Toxic 3
Pathogen Indicators 0
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 1
BioIntegrity Fair
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude