Mad Creek IA 01-NEM-81

mouth (S36 T77N R2W Muscatine Co.) to confluence with unnamed tributary in SE 1/4 S13 T77N R2W Muscatine 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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

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Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 9/17/2020 7:54:55 AM
Updated: 10/12/2020 2:56:36 PM

Use Support

Class A3

Recreation - Children's contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2010

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A3 use remains assessed as “not supported” due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. All other designated uses were "not assessed".

Assessment Explanation

Data Sources:

The source of information for this assessment remains the results of bacteria monitoring during recreational seasons of 2004 through 2009 at three stations in this segment of Mad Creek monitored as part of an IDALS/Division of Soil Conservation watershed project: (1) station 50 near the mouth of Mad Creek, (2) station 66 in the city of Muscatine, and (3) station 49 downstream from Hwy 38 north of Muscatine.

Class A3 - Indicator Bacteria:

The Class A3 (children’s recreation) use remains assessed as "not supported" based on levels of indicator bacteria during the recreational seasons of 2004 through 2009 that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) at all three monitoring stations of the IDALS/DSC project exceeded the Iowa water quality criterion to protect children’s recreation uses. The geometric means of E. coli bacteria at these stations were as follow: Station 50 (near mouth): 702 orgs/100ml in 7 samples with 71% of the samples greater than the single sample maximum criterion of 235 orgs/100 ml.; Station 66 (in Muscatine): 601 orgs/100 ml in 10 samples with 70% of the samples greater than the single sample maximum criterion of 235 orgs/100 ml.; Station 49 (north of Muscatine, dstr Hwy 38): 980 orgs/100ml in 11 samples; all 11 samples exceeded the single sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, the Class A3 uses are assessed (monitored) as not supported; this impairment will be added to Iowa’s 2010 Section 303(d) list of impaired waters.

Class BWW2 - No Data

Monitoring and Methods

Assessment Key Dates

5/18/2004

Non-fixed Monitoring Start Date

10/2/2009

Non-fixed Monitoring End Date

Methods

150

Monitoring data more than 5 years old

220

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

420

Indicator bacteria monitoring