Assessment Comments

Assessment is based on results from DNR monthly monitoring station near Elkport, Clayton County.

Basis for Assessment

SUMMARY:  Class A (primary contact recreation) uses remain assessed as "not supported."  The Class B(WW) aquatic life uses are assessed as "fully supported."  Fish consumption uses remain "not assessed."  EXPLANATION:  The assessments of support of beneficial uses are based on results of DNR monthly water quality monitoring conducted on the Volga River near Elkport during the 1998-1999 biennial period.   The Class A (primary contact recreation) uses remain assessed as "not supported."  All 14 samples from this station that were analyzed for indicator bacteria (fecal coliforms) during summers of 1998 and 1999 were collected at conditions of normal to low flow (i.e., the river was not materially affected by surface runoff).   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 14 non-runoff-affected samples was 657 orgs/100 ml, with seven samples (50%) exceeding the EPA-recommended single-sample maximum value of 400 orgs/100 ml.   The geometric mean (657 orgs/100 ml) is more than three 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 above).   The Class B(WW) aquatic life uses were assessed as "fully supported" due to the lack of violations of state water quality criteria for pH, dissolved oxygen, and ammonia-nitrogen in the 24 samples during the 1998-1999 biennial period.   In addition, no violations of Class B(WW) chronic criteria occurred in the two samples analyzed for toxic metals during the biennial period.   The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.