Rock Creek IA 02-CED-493

mouth (S2 T79N R3W Cedar Co.) to confluence with unnamed tributary in SW 1/4 S11 T80N R3W Cedar 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 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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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 12:23:30 PM
Updated: 8/2/2019 1:30:00 PM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Fully Supported

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class B(WW-1) aquatic life uses remain assessed (evaluated) as "fully supported" based on results of DNR/SHL biological sampling in 2008, 2012 and 2016. The Class HH (fish consumption) uses are assessed (monitored) as "fully supporting" based on 2016 DNR fish tissue sampling. The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of data upon which to base an assessment.

Assessment Explanation

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supporting” based on data collected in 2008, 2012 and 2016 as part of the DNR/SHL stream biocriteria project.The 2016 FIBI score was 72 (excellent) and the BMIBI score was 65 (good).The 2012 FIBI score was 65 (good) and the BMIBI score was 50 (fair). The 2008 FIBI score was 61 (good) and the BMIBI score was 74 (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 BIC 3/3 times and passed the BMIBI BIC 2/3 times in the last nine years.

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 over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous nine years (2008-2016).

Class HH (fish consumption) uses are assessed as "fully supported" based on results of DNR fish tissue monitoring near Tipton in 2016. The average level of mercury in the tissue plugs from three smallmouth bass in 2016 was 0.203 ppm (SD=0.068). The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. The levels of contaminants in the tissue samples from fish collected at Tipton do not exceed any of Iowa’s consumption advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.

Monitoring and Methods

Assessment Key Dates

8/20/2008

Biological Monitoring

9/27/2012

Biological Monitoring

9/7/2016

Biological Monitoring

9/7/2016

Fish Tissue Monitoring

Methods

150

Monitoring data more than 5 years old

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

380

Quantitative physical habitat assessment