Assessment Comments

Assessment is based on: (1) IDNR monthly fixed station monitoring near Elkport (station 10220002) from January 2010 through December 2012, results of IDNR TMDL monitoring from May 2011 through November 2012, and (3) results of IDNR/SHL biological sampling in 2006, 2008, 2012 and 2013.

Basis for Assessment

SUMMARY:  The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 4a) due to levels of indicator bacteria (E.  coli) that exceed Iowa’s water quality standards.   The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported" (IR 2a) based on results of IDNR/SHL biological sampling in conducted in 2006, 2008, 2012 & 2013.   Fish consumption uses remain "not assessed" (IR 3a) due to the lack of fish contaminant monitoring in this river reach.   Sources of data for these assessments include results of (1) IDNR monthly fixed station monitoring near Elkport (station 10220002) from January 2010 through December 2012, (2) IDNR TMDL monitoring at Littleport (Site 32; STORET Station 11220008) from May 2011 to November 2012, and (3) based on results of IDNR/SHL biological sampling in conducted in 2006, 2008, 2012 & 2013.  

Note:  A TMDL for pathogen indicators in this segment of the Volga River was prepared by IDNR and approved by EPA in 2006.   Because the primary Section 303(d) impairment identified for the 2006 assessment/listing cycle (indicator bacteria) was addressed by the TMDL, this waterbody was moved from IR Category 5a from the 2004 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2006 cycle.   Subsequent biological monitoring indicated a biological impairment not covered by the TMDL; thus, this waterbody was placed in Category 5b-v of the 2010 Integrated Reporting cycle.   However, recent biological sampling data (2008, 2012 & 2013) indicates that the aquatic life uses of this segment are fully supporting and the aquatic life use impairment is removed for the 2014 IR cycle.  

EXPLANATION:  The Class A1 (primary contact recreation) are assessed as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria.   The geometric means of indicator bacteria (E.  coli) in the 39 samples collected during the recreational seasons of 2010 through 2012 at the IDNR/SHL ambient station near Elkport were as follows:  the 2010 geometric mean was 358 orgs/100 ml, the 2011 geometric mean was 133 orgs/100 ml and the 2012 geometric mean was 174 orgs/100 ml.   All three geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml.   Twelve of the 39 samples (31%) 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.”  This river reach has a history of high levels of indicator bacteria, with assessments of either "partial support" or "nonsupport" of the primary contact recreation uses made since the 1992 Section 305(b) report.  

Note:  the above geometric means of E.  coli at station 10220002 are based on raw data for the 39 samples collected during the recreation seasons of 2010 through 2012 (eight samples in 2010, 15 samples in 2011, and 16 samples in 2012).   If serially correlated samples in these dataa (i.e., bacteria samples collected within one to three days) are averaged, the 2011 geometric mean of the ten independent samples becomes 154 orgs/100 ml and the 2012 geometric mean of the ten independent samples becomes 245 orgs/100 ml.   Ten of the 28 samples (36%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml.   Thus, whether raw data or averaged data are used, the results of monitoring at this station suggest “nonsupport” of the presumptive Class A1 (primary contact recreation) uses.  

Results of IDNR TMDL bacterial monitoring on the Volga River at Littleport (Site 32) also suggest impairment of the Class A1 uses due to geometric means of indicator bacteria that exceed the Class A1 criterion.   The geometric means of indicator bacteria (E.  coli) in the 15 samples collected during the recreational seasons of 2011 and 2012 at the this station were as follows:  the 2011 geometric mean of seven samples was 186 orgs/100 ml and the 2012 geometric mean of eight samples was 282 orgs/100 ml.   Similar to the results from the IDNR ambient monitoring station, both geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml.   Four of the 15 samples (27%) 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.”

The results of IDNR ambient water quality monitoring from 2010 through 2012 suggest "full support" of the Class B(WW1) uses due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the approximately 30 samples during this three-year period.   Results of TMDL monitoring are similar with no violations of water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the approximately 15 samples from May 2011 through November 2012.  

In agreement with the recent water quality results, the aquatic life use assessment based on IDNR/SHL biological sampling conducted in 2006, 2008, 2012 and 2013 as part of IDNR/SHL stream sampling projects, suggest “full support” of the Class B(WW1) aquatic life uses.   A series of biological metrics which 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 that were 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 2006 FIBI score was 78 (excellent) and the 2006 BMIBI score was 75 (good).   The 2008 BMIBI score was 42 (fair).   The 2012 BMIBI score was 75 (good).   The 2013 BMIBI score was 67 (good).   The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.   The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.   This segment passed the FIBI BIC 1/1 times in 2006 and passed the BMIBI BIC 3/4 times in the last eight years.   The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.   This aquatic life use assessment is considered "monitored" because there were two or more BMIBI samples collected in multiple years over a recent five-year period.  

The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.