Middle Fork Little Maquoketa River IA 01-TRK-138

Assessment Comments

Assessment remains based on 2004 IDNR/UHL biological monitoring data: 4/8, 4/8, and 3/4 coldwater biological indicators met the criteria - partially supporting (PS).

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 (evaluated) as "partially supported" based on based on results of REMAP stream biological monitoring in 2004.    Fish consumption uses remain "not assessed."  

EXPLANATION:  The assessment of the Class B(CW1) aquatic life uses was based on biological data collected in 2004 as part of the IDNR/UHL stream REMAP 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).    When fish sampling is not conducted, assessments are based on benthic macroinvertebrate data only.    Non-fish sampled sites that score 3 or 4 are fully supporting (FS), sites that score 1 or 2 are partially supporting, and sites that score 0 are not supporting (NS).    The 2004 coldwater biological indicator scores were 4/8, 4/8, and 3/4.    The aquatic life use support was assessed (evaluated) as partially supporting (=PS), 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 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 between 2004 and 2008 to be considered “monitored”.   This segment had multiple samples collected in 2004; however, the samples were not collected in multiple years.   According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report).   IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).   However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.

In partial contrast to the biological sampling data, the updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, indicates the Class B(CW1) uses should be assessed "fully supported".    According to the updated summary, Middle Fork Little Maquoketa River (a.k.a.   Bankston Cr.) 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.  

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.