Storybook Hollow IA 01-TRK-118

Assessment Comments

Assessment based on 2007 IDNR/SHL biological monitoring data (CBI = 57; CW BIC = 60) and on a 2011 survey of trout reproduction prepared by the IDNR Fisheries Bureau.

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, 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 Class A1 (primary contact recreation) uses and the Class A2 (secondary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The Class B(CW1) coldwater aquatic life uses remain assessed (evaluated) as "fully supported" based on 2007 IDNR/SHL benthic macroinvertebrate sampling data and on the February 2011 summary of trout reproduction in Iowa streams prepared by the IDNR Fisheries Bureau.   Fish consumption uses remain "not assessed."  

EXPLANATION:  The Class A1 (primary contact recreation) uses and the 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 assessment of the Class B(CW1) aquatic life uses was based on data collected in 2007 as part of the IDNR/SHL coldwater stream sampling project.   A series of biological metrics which reflect coldwater stream water quality and habitat integrity were calculated from the biological sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa that were collected in the stream sampling reach.   The biological metrics were combined to make a coldwater benthic index (CBI).   The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2007 CBI score was 57.  The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the CBI score with biological impairment criteria (BIC) established for the 2012 Section 305(b) report.  The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011.  The CW BIC is 60 and this segment passed the CW BIC 1/1 times in 2007 with the aid of the 8 point CBI UAV (uncertainty adjustment value) applied to single samples.  

This Class B(CW1) coldwater aquatic life uses are also assessed (evaluated) as “fully supporting” based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in February 2011.   According to the updated summary, Storybrook Hollow 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 are not capable of maintaining a viable population of the listed species at this time.  

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 2007.   Despite this change in assessment methodology and type, this waterbody was placed in IR Category 2a.  

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