Assessment Comments

Assessment is based on: (1) results from the IDNR ambient monthly monitoring station from 2010 through 2012 near St. Joseph in Kossuth County (STORET station 10550001), (2) results of IDNR/SHL biological sampling conducted in 2003, 2008, 2011 and 2012 and (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring near Algona in 2002 and 2008.

Basis for Assessment

[Note 1:  Prior to the 2004 assessment, this segment was referred to as IA 04-EDM-0010_2.   It was broken into two segments, now listed as IA 04-EDM-0010_2 and IA 04-EDM-0010_3 to reflect the location descriptions and classifications as described in the Surface Water Classification.   All previous assessments referring to the original segment (IA 04-EDM-0010_2) can now be found listed in the documentation for segment IA 04-EDM-0010_3.]

[Note 2:  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 in 2007,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 "not supported" (IR 4a) due to levels of indicator bacteria (E.  coli) that exceed state water quality criteria.   The Class B(WW1) aquatic life uses are assessed (evaluated) as "partially supported" (IR 3b-u) based on results of biological sampling in 2003, 2008, 2011 and 2012.   Fish consumption uses remain assessed (evaluated) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2002.   The sources of data for this assessment include (1) results from the IDNR ambient monthly monitoring station from 2010 through 2012 near St.  Joseph in Kossuth County (STORET station 10550001), (2) results of IDNR/SHL biological sampling conducted in 2003, 2008, 2011 and 2012, and (3) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring near Algona in July 2002 and 2008.  

[Note 3:  A TMDL for indicator bacteria (E.  coli) was prepared by IDNR and approved by EPA in January 2009.   Thus, the bacteria impairment for this segment is placed in IR Category 4a (impaired; TMDL approved).]

EXPLANATION:  The Class A1 uses are assessed (monitored) as "not supported" based on results of monitoring for indicator bacteria (E.  coli).   The geometric means of indicator bacteria (E.  coli) in the 24 samples collected during the recreational seasons of 2008 through 2010 at IDNR station 10550001 near St.  Joseph were as follows:  the 2010 geometric mean was 219 orgs/100 ml, the 2011 geometric mean was 155 orgs/100 ml, and the 2012 geometric mean was 64 orgs/100 ml.   The 2010 and 2012 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2012 geometric mean is well-below the Class A1 criterion.   Nine of the 24 samples (38%) 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 are "not supported" (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.”  

The Class B(WW1) aquatic life uses are assessed (evaluated) as “partially supporting” based on data collected in 2003, 2008, 2011 and 2012 as part of the IDNR/SHL stream ambient biological and REMAP sampling projects.   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 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 2003 FIBI score was 48 (fair).   The 2008 BMIBI score was 48 (fair), the 2011 BMIBI score was 44 (fair) and the 2012 BMIBI scores were 54 (fair) and 57 (good).   The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008.   The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62.   This segment passed the FIBI BIC 1/1 times in 2003 and passed the BMIBI BIC 0/4 times in the last five years.   This assessment is considered evaluated because the drainage areas (977 and 927 mi2) above the sampling sites were greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed the FIBI BIC (1/1) and failed the BMIBI BIC (0/4), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.   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).  

Despite the results of biological monitoring that suggest “partial support” of the Class B(WW1) aquatic life uses, results of chemical/physical water quality monitoring also from 2010-12 suggest “full support” of these uses.   None of the 36 samples collected during the 2010-2012 assessment period violated Class B(WW1) water quality criteria for dissolved oxygen, pH, ammonia-nitrogen, temperature, chloride, or sulfate.    

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring near Algona in 2002 and 2008.   The composite samples of fillets from channel catfish and walleye in 2002 had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.069 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.154 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   Follow-up sampling of walleye was conducted in 2008.   The level of mercury in the composite sample of walleye fillets in 2008 was 0.14 ppm.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   The fish contaminant data generated from the 2008 RAFT sampling conducted at this river show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.