Lime Creek IA 02-CED-525

from confluence with unnamed tributary (S1 T87N R10W Buchanan Co.) to confluence with unnamed tributary in SW 1/4 S11 T88N R10W Buchanan 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: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 8/2/2019 1:29:33 PM
Updated: 8/2/2019 1:30:30 PM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study

TMDL Priority

Tier III

Class BWW2

Aquatic Life - Warm Water Type 2

Fully Supported

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 uses remain assessed as “not supported” due to levels of indicator bacteria that violate Class A1 criteria. The Class B(WW2) aquatic life uses remain assessed as "fully supported" based on results of DNR-sponsored monitoring in 2010 and 2011. The sources of data for this assessment remain the results of monitoring at two stations on Lime Creek sampled from May 2010 to July 2011: STORET station 15100007 at 240th Street and STORET station 15100008 at 250th Street.

Assessment Explanation

The presumptive Class A1 uses remain assessed (monitored) as "not supported" based on results of monitoring for indicator bacteria (E. coli) at the two stations. The geometric mean of indicator bacteria (E. coli) in the 12 samples collected at Station 15100007 at 240th Street during the recreational season of 2010 (637 orgs/100 ml), and the geometric mean of the 12 samples collected during 2011 (946 orgs/100 ml) both exceeded the Class A1 criterion of 126 orgs/100 ml. Twenty of the 24 samples (83%) collected at this station exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. Similarly, the geometric mean of indicator bacteria (E. coli) in the 12 samples collected at Station 15100008 at 250th Street during the recreational season of 2010 (677 orgs/100 ml), and the geometric mean of the 11 samples collected during 2011 (957 orgs/100 ml) both exceeded the Class A1 criterion of 126 orgs/100 ml. Twenty-one of the 23 of the samples (91%) from this station 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 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).

The Class B(WW-2) aquatic life uses remain assessed (monitored) as "fully supported" based on results of chemical/physical water quality monitoring from 2010 to 2011 at stations 1510007 and 15100008. No violations of Class B(WW2) water quality criteria for temperature occurred in the combined 48 samples analyzed from May 2010 to July 2011. One of the 24 samples (4%) collected at station 15100007 violated the Class B(WW2) criterion for dissolved oxygen. The sample collected on August 3, 2010, contained 4.0 mg/l of dissolved oxygen, thus violating the criterion of 5.0 mg/l. Similarly, one of the 24 samples (4%) collected at this station violated the Class B(WW2) criterion for pH. The sample collected on June 8, 2011, contained a pH of 6.3 units, thus violating the Class B(WW2) criterion of 6.5 units. According to U.S. EPA guidelines for Section 305(b) reporting, if more than 10% of samples exceed state criteria for conventional parameters such as dissolved oxygen or pH, the aquatic life uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). According to DNR’s assessment/listing methodology, however, the results from station 15100007, however, do not indicate that significantly greater than 10% of the samples exceed the Class B(WW2) criterion. Thus, the results of chemical/physical water quality monitoring in 2010 and 2011 in this segment suggested that the Class B(WW2) aquatic life uses should be assessed (monitored) as “fully supported.”

Monitoring and Methods

Assessment Key Dates

5/19/2010

Fixed Monitoring Start Date

7/29/2011

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