Turkey River IA 01-TRK-156

The presumptive Class A1 (primary contact recreation) uses are assessed as "partially supported" based on levels of indicator bacteria that slightly exceeded state water quality criteria.  The geometric means of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2012 through 2014 at monitoring station 15450015 were as follows:  the 2012 geometric mean was 284 orgs/100 ml, the 2013 geometric mean was 606 orgs/100 ml, and the 2014 geometric mean was 180 orgs/100 ml.  All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml.  Fourteen of the 23 samples (61%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.” 

Results of chemical/physical water quality monitoring in from 2012 through 2014 do not suggest impairment of the Class B(WW2) aquatic life uses.  Monitoring at station 15450015 (TR90) showed no violations of Class B(WW1) water quality criteria for ammonia (16 samples), dissolved oxygen (24 samples), pH (24 samples), or chloride (16 samples).  Thus, the Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported”.

In agreement with the water quality sampling, this monitored biological assessment based on data collected in 2010, 2011, 2013 and 2014 as part of the IDNR Fisheries Bureau sampling project also suggests that the Class B(WW1) aquatic life uses are "fully supporting".  A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data.  The biological metrics are based on the numbers and types of fish species collected in the stream sampling reach.  The biological metrics were combined to make a fish community index of biotic integrity (FIBI).  The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).  The 2010, 2011, 2013 and 2014 FIBI scores were 69, 69 (both good) and 73, 75 (both excellent).  The aquatic life 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 biological data collected at stream ecoregion reference sites from 1994-2008.  While it is still undetermined if the Fisheries sampling sites contain stable riffle habitat, this segment passed the riffle FIBI BIC (4/4 times).  The riffle habitat FIBI BIC for this ecoregion is 65.

This aquatic life assessment is now considered "monitored" 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 in the most recent five year period (2010-2014) to be considered “monitored”.  This segment had four samples collected in the previous five years (2010-2014).