Cox Creek IA 01-VOL-304

Alternate name(s) for this segment: Alderson Hollow

confluence with Kleinlein Cr. (S36 T92N R6W Clayton Co.) to south line of S12 T91N R6W Clayton Co.

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2012 - 2014
Stream/River Water Quality Data	CY 2012 - 2014
Lake Water Quality Data	CY 2010 - 2014
Biological Sampling Data	CY 2010 - 2014*
Fish Kill Data	CY 2010 - 2014
Fish Tissue Sampling Data	CY 2010 - 2014
Continuous Dissolved Oxygen Sampling Data	CY 2010 - 2014
*Biological sites sampled in both 2009 and 2013 were also assessed.

Open Segment Map
View assessment methodology in new window

Cycle: 2016
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 8/25/2016 10:18:34 AM
Updated: 11/29/2016 11:18:27 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class A2

Presumptive Use

Recreation - Secondary contact

Not Assessed

Class BCW1

Aquatic Life - Cold Water Type 1

Partially Supported

Biological: low aquatic macroinvertebrate IBI

Support Level

Partially Supported

Impairment Code

5b-v - Biological - verified

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

Class HH

Human Health -

Not Assessed

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 and the presumptive Class A2 (secondary contact recreation) uses are "not assessed" (IR 3a) due to the lack of data for indicator bacteria upon which to base an assessment. The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "partially supported" (IR 5b-v) based on 2011 and 2013 IDNR/SHL biological sampling data. Fish consumption (Class HH) uses are "not assessed" (IR 3a).

Assessment Explanation

The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2011 and 2013 as part of the IDNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2011 CBI score was 47 and the 2013 CBI score was 42. The aquatic life use support was assessed (monitored) as partially supporting (=PS), based on a comparison of the CBI score with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 0/2 times in the last five years (2010-2014).

This aquatic life assessment is considered "monitored" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.

Monitoring and Methods

Assessment Key Dates

9/20/2011

Biological Monitoring

9/17/2013

Biological Monitoring

Methods

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

380

Quantitative physical habitat assessment