Assessment Comments

Assessment is based on results of (1) IDNR monthly fixed station monitoring near Elkport from 2002-04, (2) IDNR/UHL TMDL monitoring conducted in May 2003 (Site 32), and (3) results of DNR/UHL biological monitoring in 2002.

Basis for Assessment

SUMMARY:  Class A (primary contact recreation) uses were assessed (monitored) as "not supported" due to high levels of indicator bacteria (E.  coli) and frequent violations of Iowa’s water quality standards.   The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported" based on results of DNR/UHL chemical/physical monitoring from 2002 through 2004 and on DNR/UHL biological monitoring in conducted in 2002.   Fish consumption uses remain "not assessed" 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 2002 through December 2004 and (2) results of DNR/UHL biological monitoring in 2002.   Too few samples (one sample for most parameters) were collected at the IDNR/UHL TMDL station (Site 32; STORET Station 11220008) to be of use for developing a water quality assessment for this river segment.

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) is addressed by the TMDL, this waterbody is moved from IR Category 5a from the 2004 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2006 cycle.

EXPLANATION: The Class A (primary contact recreation) uses remain assessed (monitored) as "not supported" due to consistently high levels of indicator bacteria and frequent violations of the relevant Iowa water quality standard.   Thirty-four samples from this station were analyzed for indicator bacteria (E.  coli) during recreational seasons of 2002 through 2004, 2001, and 2002.    Due to recent changes in Iowa’s Water Quality Standards, Iowa’s 2006 assessment methodology for indicator bacteria has changed.   Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses:  the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff."  Due to a change in the Standards in July 2003, E.  coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E.  coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.”  Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E.  coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of the 2006 Section 305(b) assessments and Section 303(d) listings.  

The geometric mean of E.  coli bacteria in the 34 samples was 248 orgs/100 ml, with 12 samples (35%) exceeding Iowa’s single-sample maximum value of 235 orgs/100 ml.   The geometric mean (248orgs/100 ml) is nearly twice the state water quality criterion of 126 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting and the IDNR assessment/listing methodology, if the geometric mean is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses are "not supported" (see pgs 3-33 to 3-35of U.S.  EPA 1997b).   This river reach has a history of high levels of indicator bacteria, with assessments of either "partial support" or "nonsupport" of the Class A uses made since the 1992 report (see assessments for previous Section 305(b) reporting cycles).  

The results of IDNR ambient water quality monitoring from 2002 through 2004 suggest "full support" of the Class B(WW) uses due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the approximately 40 samples during the 2002-2004 period.   In addition, no violations of Class B(WW) chronic criteria occurred in the samples analyzed for pesticides during this period.   Of the ten samples analyzed for toxic metals, only one sample violated a Class B(WW) criterion:  one of the ten samples analyzed for lead exceeded the Class B(WW) criterion of 30 ug/l.  This violation occurred on July 6, 2004; the level of lead in the sample was 60 ug/l.   According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-18), however, one violation of a water quality criterion for a toxic pollutant in an abundant data set (at least 10 samples over at three-year period) does not indicate an impairment of aquatic life uses.  

Results of DNR/UHL biological monitoring in 2002, conducted as part of the DNR/UHL stream biocriteria project, also suggest “full support” of the Class B(WW) 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 (F-IBI) and a benthic macroinvertebrate index (BM-IBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2002 Fish IBI score was unavailable and the BM-IBI score was 56 (good).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the BM-IBI score with biological assessment criteria established for previous Section 305(b) reports.   The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.

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