Bridge Creek IA 03-NSK-1898

mouth (T75N R11W Sec18 Keokuk Co.) to headwaters (T77N R12W Sec30 Keokuk 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 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
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Cycle: 2016
Release Status: Final
Overall IR: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Unknown
Created: 9/23/2016 7:23:51 AM
Updated: 9/23/2016 7:23:51 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

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 "not assessed" (IR 3a) due to the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life use assessment was historically based on 1999 Fisheries Bureau data (see below). Due to the age of these data (> 10 years), the aquatic life uses are now considered "not assessed" (IR 3a).

Assessment Explanation

Assessment historically based on 1999 Fisheries Bureau data (see below). Due to the age of these data (> 10 years), the aquatic life uses are now considered "not assessed" (IR 3a).

[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

The presumptive Class B(WW1) aquatic life uses was remain assessed (evaluated) as “fully supporting” based on data collected in 1999 as part of an IDNR Fisheries stream sampling project: Manchester research station. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data. The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 evaluated FIBI was 31 (fair). The aquatic use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 36.

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 over a five-year period to be considered “monitored”. This segment had a single sample collected in 1999. Additionally, because these data are now considered too old (>10 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).

Monitoring and Methods

Assessment Key Dates

None listed

Methods

150

Monitoring data more than 5 years old