Assessment Comments

Assessment is based on results of (1) IDNR monthly fixed station monitoring near Elkport from 2000-02, (2) IDNR/UHL monthly TMDL monitoring conducted from March to November, 2001 (Sites 33 & 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 and frequent violations of Iowa’s water quality standards.   The Class B(WW) aquatic life uses were assessed (monitored) as "fully supported / threatened" based on results of DNR/UHL biological monitoring 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 2000 through December 2002, (2) IDNR/UHL monthly monitoring conducted from March to November, 2001, near Mederville (Site 33) and Littleport (32) in support of TMDL development for this river reach, and (3) results of DNR/UHL biological monitoring in 2002.  

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.   Of the 28 samples from this station analyzed for indicator bacteria (fecal coliforms) during recreational seasons of 2000, 2001, and 2002, three samples were collected during conditions of high river flow.   These high flows resulted in monitoring at river discharges that exceeded the long-term monthly average flow plus one standard deviation of this average (flow statistics from Fischer et al.  1990 and Fischer and Eash 1998).   For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff.   According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff."  The geometric mean of fecal coliform bacteria in the 25 non-runoff-affected samples was 893 orgs/100 ml, with 17 samples (68%) exceeding the EPA-recommended single-sample maximum value of 400 orgs/100 ml.   The geometric mean (893orgs/100 ml) is over four times the state water quality criterion of 200 orgs/100 ml.   According to U.S.  EPA guidelines for Section 305(b) reporting, if the geometric mean is greater than 200 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).   Results of IDNR monitoring conducted in 2001 in support of TMDL development for this river reach are consistent with this assessment.   The 2001 seasonal geometric mean of the six non-flow affected samples from near Mederville was 294 orgs/100 ml; the geometric mean of the six non-flow affected samples from near Littleport was 264 orgs/100 ml.   Both these geometric means suggest nonsupport of the Class A uses.   The source of the high levels remains unknown.   Additional TMDL-related monitoring was conducted in 2001 on the following Volga River tributaries in river reach:  Bear Creek near Elkport (Site 37) and Doe and Honey creeks near Littleport (Sites 38 and 39, respectively).   Results of this monitoring show extremely high levels of fecal coliform bacteria in these tributaries, with the 2001 recreational season geometric means as follows (N=7; stream flows not evaluated for effects of runoff):  Bear Creek near Elkport:  698 orgs/100 ml; Doe Creek near Littleport:  5,055 orgs/100 ml; Honey Creek near Littleport:  1,465 orgs/100 ml.   Further investigation is needed to determine (1) whether these high fecal levels in these and other tributaries are influencing levels in the Volga River and (2) the sources of the high fecal levels in these tributaries.  

The results of IDNR ambient water quality monitoring 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 44 samples during the 2000-2002 period.   In addition, no violations of Class B(WW) chronic criteria occurred in the samples analyzed for pesticides during this period.   Results of monitoring conducted in support of TMDL development near Mederville and Littleport are consistent with this assessment:  none of the nine monthly samples from these stations violated state water quality criteria for dissolved oxygen or pH.  

Despite the results of IDNR ambient water quality monitoring that suggest “full support” of the Class B(WW) uses, the results of DNR/UHL biological monitoring in 2002, conducted as part of the DNR/UHL stream biocriteria project, suggest a threat to this full support.   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/threatened (=FS/T), 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.