South Fork Catfish Creek IA 01-TRK-130

The Class A1/A3 (primary contact recreation) uses remain assessed (monitored) as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria.  The geometric means of indicator bacteria at all three monitoring stations far exceeded the Class A1/A3 geometric mean criterion of 126 org/100 ml to protect primary contact recreation uses.  In addition, all 33 samples collected at these stations in 2010 exceeded the single-sample maximum criterion to protect primary contact recreation.  The geometric mean of indicator bacteria (E. coli) in the 11 samples collected approximately every two weeks during the recreational season of 2010 at Site WQ-08 of the Catfish Creek Watershed Project (3,983 orgs/100 ml) far exceeded the Iowa water quality criterion to protect primary contact recreation uses (126 orgs/100 ml); all 11 samples (100%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml for primary contact uses.  Similarly, at Station WQ-10, the geometric mean of E. coli  in the 10 samples collected (2,860 orgs/100 ml) also far exceeded the Class A1/A3 geometric mean criterion and all 11 samples exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml.  The geometric mean of the 11 samples collected at Site WQ-14 during 2010 (4,369 orgs/100 ml) also far exceeded the Class A1/A3 geometric mean criterion with, again, all 11 samples (100%) exceeding the Class A1/A3 single-sample maximum criterion.  According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 630 orgs/100 ml., the secondary contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported” based on biological monitoring conducted in 2002 (IR Category 2a).   This evaluated biological assessment was based on data collected in 2004 as part of the IDNR/SHL stream REMAP project.   A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach.   The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 FIBI score was 76 (excellent) and the BMIBI score was 77 (excellent).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.   The FIBI BIC for this ecoregion is 56 and the BMIBI BIC for this ecoregion is 61.

Also, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).