Volga River IA 01-VOL-290
from confluence with Cox Cr. (S21 T92N R5W Clayton Co.) to bridge crossing in Volga (north line S10 T92N R6W Clayton Co.).
SUMMARY: The Class A1 (primary contact recreation) uses remain assessed (evaluated) as "not supported" (IR 4a) based on levels of indicator bacteria that violate state water quality standards. The Class B(WW1) aquatic life uses are considered “not assessed” (IR 3a) due to the lack of recent water quality data upon which to base an assessment. 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 remains 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. The water quality data upon which these assessments are based are now more 10 years old. Despite the age of the data used for this assessment, the impairment of the Class A1 uses remains until more recent data suggest a good cause for de-listing.
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 was moved from IR Category 5a from the 2004 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2006 cycle; this waterbody remains in IR Category 4a. The fish consumption uses remain "not assessed" due to the lack of recent fish tissue monitoring in this river reach.
EXPLANATION: The Class A1 (primary contact recreation) uses remain assessed (evaluated) as "partially" due to high levels of indicator bacteria. The geometric mean level of indicator bacteria (E. coli) at both Volga River monitoring stations in 2001 exceeded in exceeded the Iowa Class A1 water quality criterion of 126 E. coli orgs/100ml, thus suggesting continued impairment of the Class A1 uses in this segment of the Volga River. The geometric mean of E. coli for the nine samples collected at Volga River station 35 was 276 orgs/100 ml; the geometric mean for the nine samples collected at Volga River station 304 was 245 orgs/100 ml. Both of these geometric means exceed the Iowa Class A1 criterion of 126 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting, if the geometric mean of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "partially supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Although the IDNR assessment/listing methodology requires at least 10 samples collected over a three-year period in order to develop a "monitored" [higher confidence] assessment appropriate for Section 303(d) listing, the numbers of samples at Volga River stations 34 and 35 (nine samples at both stations) are considered sufficient to justify this impairment.
The assessment of support of the Class B(WW1) aquatic life uses is changed from “fully supported” to “not assessed” due to the age of the water quality data (greater than 10 years) upon which the original assessment was based. According to Iowa DNR’s assessment/listing methodology, as data age beyond 10 years, they are no longer considered appropriate for characterizing current water quality conditions. Thus, because the most recent data available for this assessment segment were collected more than 10 years ago, the aquatic life uses of this segment are now considered “not assessed”.