Assessment Comments
Assessment remains based on results of fish contaminant monitoring conducted near the Volga River Recreation Area in 2001, 2005, 2007, 2008 and 2012 as part of U.S. EPA/IDNR fish contaminant (RAFT) monitoring.
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, 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 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 remain "not assessed" (IR 3a) due to lack of information on levels of indicator bacteria in this river segment. The Class B(WW1) aquatic life uses are now considered “not assessed” (IR 3a) due to lack of recent data upon which to base an assessment. Fish consumption uses remain assessed (monitored) as “partially supported” (IR 5a) based on fish contaminant monitoring in 2001, 2005, 2007, 2008 and 2012. The source of data for this assessment is the results of fish contaminant monitoring conducted near the Volga River Recreation Area in 2001 and 2005, 2007, 2008 and 2012 as part of U.S. EPA/IDNR fish contaminant (RAFT) monitoring.
EXPLANATION: The Class A1 (primary contact recreation) uses remain "not assessed" due to lack of information on levels of indicator bacteria in this river segment.
While the Class B(WW1) aquatic life of this segment were previously assessed (evaluated) as "fully supported" based on results of TMDL monitoring and IDNR biological monitoring in 2000, these data are now considered too old (greater than 10 years) for assessing current water quality conditions. Thus, the Class B(WW1) aquatic life uses are not considered “not assessed”. As water quality data age, they become less able to represent current water quality conditions. Thus, according to IDNR’s assessment/listing methodology, waterbodies with assessments based on data older than ten years will be considered “not assessed” unless the previous assessment indicated impairment of the assessed use.
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, 2008 and 2012. Results from these samplings demonstrated elevated levels of mercury in smallmouth bass fillets such that a restricted consumption advisory was issued by Iowa DNR in 2006; this advisory remains in effect. This advisory recommends consumption of no more than one meal per week of smallmouth bass from this river segment. 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 which also exceeded the IDNR/IDPH advisory trigger level of 0.3 ppm for a one meal per week advisory. 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 covered the segments of the Volga River upriver from the county road C2W bridge at Volga in western Clayton County. Follow-up monitoring was conducted as part of the RAFT program in 2007 and 2008. The 2007 samples of smallmouth bass fillets contained 0.24 ppm of mercury; the 2008 sample of smallmouth bass fillets contained 0.33. Because the level of mercury in the 2008 sample exceeded the IDNR/IDPH advisory trigger level of 0.3 ppm, the advisory issued in 2006 continued. Results of from the 2012 RAFT showed that levels of mercury in the five smallmouth bass sampled ranged from 0.16 to 0.27 ppm with an average level of mercury of 0.214 (standard deviation of 0.051 ppm). This level of mercury is below Iowa’s threshold for a one mean/week advisory of 0.3 ppm of mercury. According to Iowa’s consumption advisory protocol, however, two consecutive samplings that show levels of fish contaminants are below the advisory threshold are needed to rescind an existing advisory. Thus, follow-up monitoring will be conducted in 2014 to better define levels of mercury in this segment of the Volga River and to determine whether the existing advisory should be rescinded.
