Assessment Comments
Assessment is based on results of IDNR/UHL monitoring in 2001 in support of TMDL development.
Basis for Assessment
SUMMARY: Class A (primary contact recreation) uses were assessed (evaluated) as "not supported" based on levels of indicator bacteria that violate state water quality standards. The Class B(WW) aquatic life uses were assessed (evaluated) as "fully supported" based on results of ambient physical/chemical monitoring. Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment. The source of data for this assessment is the results of IDNR/UHL monthly monitoring conducted from March to November, 2001, near Osborne (Site 34) and Volga (Site 35) in support of TMDL development for this river segment.
EXPLANATION: The Class A (primary contact recreation) uses remain assessed as "not supported." Of the 14 total samples from these two Volga River stations analyzed for indicator bacteria (fecal coliforms) during the recreational season of 2001, only one sample (site near Osborne) was collected during conditions of high river flow. This high flow 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 means of fecal coliform bacteria at the three sites were as follows: Osborne: 359 orgs/100 ml (N=7); 1.5 miles SE Volga: 546 ors/100 ml (N=7); downstream from the Volga wastewater treatment plant: 625 orgs/100 ml). These geometric means are well above 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. 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: Cox Creek NW of Mederville (Site 40) and Hewitt and Pine creeks near Volga (Sites 41 and 42, 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): Cox Creek near Mederville: 1,926 orgs/100 ml; Hewitt Creek near Volga: 546 orgs/100 ml; Pine Creek near Volga: 982 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 Class B(WW) aquatic life uses were assessed as "fully supported" due to the lack of violations of state water quality criteria for pH and dissolved oxygen in the nine samples collected from each of the two Volga River TMDL monitoring stations during 2001. These samples were not analyzed for either ammonia, toxic metals, or toxic organic compounds.
The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.
