Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Cedar River IA 02-CED-472

from W. Fk. Cedar R. (S4, T90N, R14W, Black Hawk Co.) to lowhead dam at Waverly in NW 1/4, S2, T91N, R14W, Bremer Co.

Assessment Cycle
2010
Release Status
Final
Result Period
2006 - 2008
Designations
Class A1 Class B(WW-1) Class HH
Assessment Type
Monitored
Integrated Report
Category 5a
Legacy ADBCode
IA 02-CED-0070_0
Overall Use Support
Partial
Aquatic Life Use Support
Fully
Fish Consumption
Not assessed
Primary Contact Recreation
Partial
Documentation
Assessment Comments

Assessment is based on results of monthly monitoring from January 2006 through December 2008 at the IDNR ambient monthly monitoring station located near Janesville in Bremer Co. (STORET station 10090001).

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this river segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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), and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria during recreational seasons of 2006 through 2008.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from 2006 through 2008.   Fish consumption uses remain not assessed due to the lack of fish contaminant monitoring in this river segment.   The source of data for this assessment is the results of monthly monitoring from January 2006 through September 2008 at the IDNR ambient monthly monitoring station located near Janesville in Bremer Co.   (STORET station 10090001).    

The Class A1 uses are assessed (monitored) as "partially supported.”  The geometric mean level of indicator bacteria (E.  coli) in the 22 samples collected during recreational seasons of 2006 through 2008 (99 orgs/100ml) is below the Iowa Class A1 water quality criterion of 126 orgs/100ml.   Eight of the 22 samples (36%) contained a level of E.  coli that exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean of E.  coli is less than the applicable state criteria, the contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35of U.S.    EPA 1997b).    Thus, these data suggest that the Class A1 uses should be assessed as “fully supported.”  The geometric mean levels of E.  coli during the previous (2008) assessment/listing cycle (112 orgs/100ml) was also below Iowa’s Class A1 criterion of 126 orgs/100ml.   These guidelines, however, also suggest that if more than 10% of samples exceed the single-sample maximum criterion for indicator bacteria, the primary contact recreation uses should be assessed as "partially supported" (see pgs 3-33 to 3-35 of U.S.   EPA 1997b).   According to IDNR’s assessment/listing methodology, the monitoring data from 2006-08 suggest that significantly greater than 10% of the samples exceed IDNR’s single-sample maximum criterion, thus suggesting that the Class A1 uses should be assessed as “partially supported/impaired.”  

The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of monitoring from the IDNR ambient station near Janesville from 2006 through 2008.   Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the 34 samples collected or for toxic metals in the two samples analyzed during this assessment period.  

Fish consumption uses are not assessed due to the lack of recent fish tissue monitoring in this river segment.

Monitoring and Methods
Assessment Key Dates
12/11/2008 Fixed Monitoring End Date
1/11/2006 Fixed Monitoring Start Date
Methods
230 Fixed station physical/chemical (conventional plus toxic pollutants)
420 Water column surveys (e.g. fecal coliform)
Monitoring Levels
Biological 0
Habitat 0
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
  • Moderate