Turkey River IA 01-TRK-154

Assessment Comments

The source of data for this assessment include results of monitoring at station TR80 SE of Cresco (STORET station 15450014) from April 2011 to November 2012.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this river segment was designated only for Class B(WW) aquatic life uses, including fish consumption uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008 and due to the completion of a Use Attainability Analysis, this segment is also now designated for Class A1 (primary contact recreation) uses.   This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported” based on results of bacterial in 2011 and 2012.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" based on results of water quality monitoring in 2011 and 2012.   Fish consumption uses remain “not assessed”.   The source of data for this assessment include results of monitoring at station TR80 SE of Cresco (STORET station 15450014) from April 2011 to November 2012.

EXPLANATION: The Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported".   The geometric means of indicator bacteria (E.  coli) in the 15 samples collected during the recreational seasons of 2011 and 2012 at station TR80 (STORET station 15450014) were as follows:  the 2011 geometric mean was 40 orgs/100 ml and the 2012 geometric mean was 74 orgs/100 ml.   Two of the 15 samples (13%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.   Both the  recreation season geometric means are well below the Class A1 criterion of 126 orgs/100 ml.   In addition, the percentage of samples that exceed Iowa’s single-sample maximum criterion is not significantly greater than 10% (see IDNR assessment/listing methodology).   According to U.S.  EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if recreation season geometric means are below Iowa’s water quality criterion, and the percentage of samples exceeding Iowa’s single-sample maximum criterion is not significantly greater than 10%, the contact recreation uses should be assessed as "fully supported" (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).  

Results of chemical/physical water quality monitoring in 2011 and 2012 do not suggest impairment of the Class B(WW1) aquatic life uses.   Monitoring at station TR80 showed no violations of Class B(WW1) water quality criteria for conventional pollutants or ammonia, dissolved oxygen, or pH in the approximately 15 samples analyzed at each station.   Thus, the Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported”.

The fish consumption uses remain “not assessed” due to the lack of information upon which to base an assessment.