2016 assessment for South Cedar Creek (aka Cedar Cr.)

South Cedar Creek (aka Cedar Cr.) IA 01-TRK-172

north line S7 T92N R3W (Clayton Co.) to north line of S30 T93N R3W Clayton Co.

2016
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

Overall IR

3 - Insufficient data exist to determine whether any designated uses are met.

Trend

Unknown

Created

8/23/2016 2:52:00 PM by

Updated

11/21/2016 2:11:30 PM by

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

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

3b-c - Use potentially biologically impaired based on calibrated IBI metrics.

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2012

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 (primary contact recreation) uses and the Class A2 (secondary contact recreation) uses are "not assessed" (IR Category 3a) due to the lack of information upon which to base an assessment. The Class B(CW1) coldwater aquatic life uses assessed (evaluated) as "partially supported" (IR Category 3b-c) based on results of 2007 benthic macroinvertebrate sampling. Fish consumption uses are "not assessed" (IR Category 3a) due to the lack of fish contaminant monitoring in this assessment segment. The source of data for this assessment remains the results of IDNR/SHL benthic macroinvertebrate sampling in 2007.

Assessment Explanation

The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2007 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 2007 CBI score was 48. The aquatic life use support was assessed (evaluated) 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 0/1 times in 2007.

This aquatic life assessment is now considered "evaluated" 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 in a five-year period to be considered “monitored”. This segment had a single sample collected in 2007. Additionally, these data are now greater than five years old. According to IDNR’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). IDNR 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).

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

Monitoring and Methods

Assessment Key Dates

9/18/2007

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

380

Quantitative physical habitat assessment