Wolf Creek IA 02-CED-530

mouth (S29 T87N R11W Black Hawk Co.) to confluence with Twelvemile Cr. in S19 T86N R13W Tama Co.

Assessment Cycle

2018

Release Status

Final

Data Collection Period

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.

Overall IR Category: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 5/13/2019 1:17:49 PM
Updated: 7/16/2019 2:37:21 PM

Assessment conducted in accordance with Iowa's 2018 IR methodology

Use Support

Class A1

Recreation

Primary contact

Presumptive Use

Partially Supported

Impairments

Support Level

Partially Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Aquatic Life

Warm Water Type 1

Fully Supported

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 remain assessed (monitored) as "partially supported" due to levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of ambient water quality monitoring conducted from 2012 through 2014 and based on results of biological sampling conducted in 2004. Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this assessment segment. The primary sources of data for this are (1) the results of DNR/SHL monthly ambient water quality monitoring conducted on Wolf Creek near LaPorte City (STORET station 10070002) during the 2014-2016 assessment period, (2) DNR/SHL REMAP biological sampling conducted in 2004 near LaPorte City, and (3) USGS monitoring at station 05464220 near Dysart from September 2012 to September 2013.

Assessment Explanation

The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2014 through 2016 at Iowa DNR ambient station 10070002 at La Porte City were as follows: the 2014 geometric mean was 200 orgs/100 ml, the 2015 geometric mean was 406 orgs/100 ml, and the 2016 geometric mean was 459 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Sixteen of the combined 24 samples (67%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported."

The Class B(WW1) aquatic life uses remains assessed (evaluated) as “fully supporting” based on data collected in 2004 as part of the DNR/SHL stream REMAP 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 45 (fair) and the BMIBI score was 50 (fair). 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 non-riffle site FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52. This site met the BMIBI BIC with the aid of the BMIBI UAV (uncertainty adjustment value applied to single samples) of 8 points. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years in a five year period. Despite this change in assessment methodology and type, this aquatic life assessment still suggests that this waterbody is fully supporting its' aquatic life uses. Also, 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).

Results of chemical/physical water quality monitoring at Iowa DNR ambient station 10070002 at La Porte City also suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.3 mg/L), 36 Dissolved Oxygen samples (minimum = 6.9 mg/L), 35 pH samples (range = 7.4 to 8.4), 36 Temperature samples (maximum = 23.5°C), 36 Chloride samples (maximum = 33 mg/L), or 36 Sulfate samples (maximum = 72 mg/L) occurred during monitoring from January 2014 to December 2016.According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this river segment. Previous assessments were based on results of fish contaminant monitoring conducted by USGS in 1995 as part of the NAWQA project. These data are now considered too old (greater than 10 years) to accurately characterize current water quality conditions.

Monitoring and Methods

Assessment Key Dates

8/19/2004

Biological Monitoring

1/9/2014

Fixed Monitoring Start Date

12/6/2016

Fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

220

Non-fixed station physical/chemical monitoring (conventional pollutant only)

230

Fixed station physical/chemical (conventional plus toxic pollutants)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

380

Quantitative physical habitat assessment

420

Indicator bacteria monitoring