North Cedar Creek IA 01-YEL-431

Assessment Comments

Assessment based on results of (1) IDNR/UHL biocriteria sampling data in 2007 & 2008: 5/8, 7/8, 5/8, 6/8 coldwater indicators met and (2) water quality and biological monitoring conducted in 2000-01 as part of the Sny Magill / Blood Run project.

Basis for Assessment

Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) aquatic life 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 also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses.   This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption) uses.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses and presumptive Class A2 (secondary contact recreation) uses remain "not assessed" due to the lack of data for indicator bacteria upon which to base an assessment.   The Class B(CW1) coldwater aquatic life uses remain assessed (monitored) as "fully supported" based on the results of biological monitoring conducted in 2007 and 2008, results of ambient water quality monitoring conducted from 2000-2001 and on the May 2006 summary of trout reproduction in Iowa streams as prepared by the IDNR Fisheries Bureau.   Fish consumption uses remain "not assessed."  The sources of data for this assessment are results of (1) IDNR/UHL biological monitoring conducted in 2005 as part of the stream biocriteria project, (2) water quality monitoring conducted at IDNR station 15220003 from January 2000 to September 2001 as part of the Sny Magill Creek Nonpoint Source Pollution Monitoring Project and (3) the May 2006 summary of trout reproduction in Iowa streams as prepared by the IDNR Fisheries Bureau.   Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach.    

EXPLANATION:  The Class B(CW1) aquatic life assessment was based, in part, on data collected in 2005 as part of the IDNR/UHL stream biocriteria project.   A series of eight (8) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data and supplemental IDNR Fisheries Bureau data.   The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach.   Sites that score 5-8 are Fully Supporting (FS), sites that score 2-4 are Partially Supporting (PS), and sites that score 0-1 are Not Supporting (NS).   The 2007 coldwater biological indicator scores were 5/8 and 7/8.   The 2008 scores were 5/8 and 6/8.   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for this Section 305(b) report.   The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2008 and with assistance from the IDNR Fisheries Bureau.  

This aquatic life use assessment is considered "monitored" because there were two or more samples collected in multiple years from 2004-2008.

In addition, the B(CW1) aquatic life assessment was based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, the Class B(CW1) uses are assessed as "fully supported".   According to the updated summary, North Cedar Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout.   Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population for the resident trout species at this time.   This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.  
  
The results of the chemical monitoring conducted on this stream segment in from 2000 through 2001 as part of the Sny Magill Creek Nonpoint Source Project also suggest "full support" of the Class B(CW1) uses.   No violations of Class B(CW1) water quality criteria for dissolved oxygen or temperature occurred in the approximately 90 samples analyzed during this period.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.