Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Silver Creek IA 01-WPS-363

from Crystal Cr. (aka Clear Cr.) (S23 T81N R3E Clinton Co.) to confluence with Negro Cr. in S27 T82N R3E Clinton Co.

Cycle
2018
Release Status
Final
Overall IR
2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend
Unknown
Created
5/13/2019 9:02:11 AM
Updated
5/13/2019 9:04:41 AM
Use Support
Class A1
Recreation - Primary contact
Not Assessed
Class BWW2
Aquatic Life - Warm Water Type 2
Fully Supported
General Use
General Use water -
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported” based on results of DNR/SHL biological sampling in 2004 and 2012.

Assessment Explanation

The Class B(WW2) aquatic life uses remains assessed (evaluated) as "fully supported" based on data collected in 2004 and 2012 as part of the DNR/SHL stream biocriteria project. A series of biological metrics which 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 2004 FIBI score was 44 (fair) and the BMIBI score was 54 (fair). The 2012 FIBI score was 57 (good) and the BMIBI score was 69 (good). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of 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 and BMIBI BICs 2/2 times in the last 13years.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years between over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 13years (2004-2016); however, the multiple samples were not collected during a five-year period. Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.

Monitoring and Methods
Assessment Key Dates
7/14/2004
Biological Monitoring
7/17/2012
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