Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Boyer River IA 06-BOY-1500

mouth (Pottawattamie Co.) to confluence with Willow R. in S28 T78N R44W Harrison Co.

Assessment Cycle
2018
Release Status
Final
Data Collection Period
Overall IR Category
3 - Insufficient data exist to determine whether any designated uses are met.
Trend
Unknown
Created
5/30/2019 1:34:38 PM
Updated
7/30/2019 12:39:55 PM
Assessment conducted in accordance with Iowa's 2018 IR methodology
Use Support
Class A1
Not Assessed
Class BWW1
WINOFI
Biological: low fish & invert IBIs- cause unknown
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2006
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
Class HH
Not Assessed
General Use
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 (primary contact recreation) and Class HH (fish consumption) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting" based on data collected in 2003 as part of the DNR/SHL stream REMAP project.

Assessment Explanation

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting based on data collected in 2003 as part of the DNR/SHL 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 2003 FIBI score was 8 (poor) and the BMIBI score was 37 (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 1994-2008. The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54. This assessment is considered evaluated because the drainage area (1,092 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 segmentfailed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn’t fall in the calibrated watershed size.

According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). 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
8/13/2003 Biological Monitoring
Methods
150 Monitoring data more than 5 years old
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
330 Fish surveys
380 Quantitative physical habitat assessment