Assessment Comments
Assessment is based on: (1) results of fish contaminant monitoring conducted near the Volga River Recreation Area in 2001, 2005, 2007, and 2008 as part of U.S. EPA/IDNR fish contaminant (RAFT) monitoring, (2) results of IDNR/UHL monitoring at TMDL site 36 in 2000, and (3) results of IDNR/Fisheries Bureau biological monitoring in 2000.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), and due to the completion of a Use Attainability Analysis in 2007, this segment is also now designated for Class A1 (primary contact recreation) uses. This stream segment remains designated for aquatic life uses (now termed Class B(WW1) aquatic life uses). Thus, for the current (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The Class A1 (primary contact recreation) uses are "not assessed" due to lack of information on levels of indicator bacteria in this river segment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported" based on (1) the lack of violations of state water quality criteria for pH and dissolved oxygen in the nine samples collected in 2000 from the TMDL monitoring station on the Volga River near at White Pine Forrest Preserve upstream from Volga (Site 36) and (2) results of IDNR/Fisheries Bureau biological monitoring in 2000. Fish consumption uses are assessed (monitored) as “partially supported” based on fish contaminant monitoring in 2001 and 2005. The sources of data for this assessment include (1) results of fish contaminant monitoring conducted near the Volga River Recreation Area in 2001, 2005, 2007, and 2008 as part of U.S. EPA/IDNR fish contaminant (RAFT) monitoring, (2) results of IDNR/UHL monitoring at TMDL site 36 in 2000, and (3) results of IDNR/Fisheries Bureau biological monitoring in 2000.
EXPLANATION: The Class A1 (primary contact recreation) uses were "not assessed" due to lack of information on levels of indicator bacteria in this river segment.
The Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported." This assessment was based on data collected in 2000 as part of an IDNR Fisheries stream sampling project: Manchester research station. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data. The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 evaluated FIBI score was 79 (excellent). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI 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 1994-2004. The FIBI BIC for this ecoregion is 52 and this segment passed the FIBI BIC 1/1 times in 2000.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”. This segment had a single sample collected in 2000. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
Fish consumption uses are assessed (monitored) as “partially supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near the Volga State Recreation Area in 2001, 2005, 2007 and 2008. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. According to IDNR’s assessment methodology, the existence of a one-meal-per-week consumption advisory indicates that fish consumption uses should be assessed as “partially supported”.
For the 2001 RAFT sampling, the composite samples of fillets of smallmouth bass contained 0.326 ppm of mercury. The level of mercury in the sample of 2005 composite sample smallmouth bass fillets was 0.545 ppm. According to the IDNR/IDPH advisory protocol, if two consecutive samplings show that contaminant levels are above the trigger level in fillet samples, issuance of a consumption advisory is justified. This advisory was issued by IDNR and IDPH in January 2006 and covers the segments of the Volga River upriver from the county road C2W bridge at Volga in western Clayton County.
Follow-up sampling was conducted in 2007 and 2008 to better determine the amount of mercury in smallmouth bass in this river segment. For the 2007 RAFT sampling, the composite samples of fillets of smallmouth bass contained 0.241 ppm of mercury. This level is below the advisory trigger level, however, two consecutive samples below the advisory trigger level are necessary to remove a fish consumption advisory. The level of mercury in the sample of 2008 composite sample smallmouth bass fillets was 0.326 ppm, which is again above the advisory trigger level. Therefore the fish consumption advisory remains justified for this river segment and the fish consumption uses remain assessed as "partially supported."
