Assessment Comments
Assessment is based on results of chemical/physical monitoring in 2011 and 2012 and on result of 2001 IDNR/SHL biological sampling data: FIBI = 68 (good), BMIBI = 84 (excellent). Non-riffle habitat FIBI BIC = 44, and natural substrate BMIBI BIC = 70. This assessment is also based on results of fish contaminant monitoring in 2001, 2005, 2007, 2008, and 2012.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) 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(WW2) water quality criteria. Also, although not designated for Human Health-Fish Consumption uses, this stream segment has been covered by a fish consumption advisory since 2006. In the opinion of Iowa DNR Fisheries Biologists, this stream segment supports harvestable populations of game fish (Smallmouth Bass). Thus, the fish consumption use is added to this assessment segment only for purposes of Section 305(b) assessment and Section 303(d) listing.
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” (IR 5p) due to violations of Iowa water quality criteria for indicator bacteria. This is a new impairment for this assessment segment. The Class B(WW2) aquatic life uses are assessed (evaluated) as "fully supported" (IR 2a) based on results of IDNR/SHL biological sampling in 2001. Fish consumption uses are assessed as “partially supporting (IR 5p) due to issuance of a one meal/week consumption advisory for Smallmouth Bass due to elevated levels of mercury. This assessment is also based on (1) results of chemical/physical monitoring from May 2011 to November 2012 at station VRN-10 (STORET station 15330014) and (2) results of Iowa DNR/U.S. EPA fish contaminant monitoring at the Volga State Recreation Area in 2001 and 2005.
EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the seven monthly samples collected during the recreational season of 2011 (416 orgs/100 ml), and the geometric mean of the eight samples collected during 2012 (723 orgs/100 ml) both exceeded the Class A1 criterion of 126 orgs/100 ml. Eleven of the combined 15 samples (73%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).
The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported.” This assessment was based on data collected in 2001 as part of the IDNR/SHL stream biocriteria project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and 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) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2001 FIBI score was 68 (good) and the BMIBI score was 84 (excellent). The aquatic life use support was assessed as fully supported (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 44 and the natural substrate BMIBI BIC for this ecoregion is 70.
This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over a five-year period. 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). Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.
Results of chemical/physical monitoring from May 2011 to November 2012 at station VRN-10 show no violations of Class B(WW2) aquatic life criteria for DO, pH, or ammonia in the 15 samples collected, thus suggesting no impacts to support of these uses.
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 and in 2005. When defining the boundaries for this advisory, Iowa DNR Fisheries Biologists recommended including this segment of the North Branch Volga River. 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. Levels of mercury in samples of smallmouth bass from consecutive samplings in 2001 and 2005 exceeded Iowa advisory trigger levels for a one meal per week advisory. 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 and includes the Little Volga River and the North Branch Volga River. 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”.
Follow-up monitoring was conducted as part of the Iowa DNR/U.S. EPA 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 meal/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.
