North Branch Volga River IA 01-VOL-330

[Note: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 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.]

The presumptive Class A1 (primary contact recreation) uses remain 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 24 samples collected during the recreational seasons of 2012 through 2014 at the station VRN-10 (STORET station 15330014) were as follows: the 2012 geometric mean was 723 orgs/100 ml, the 2013 geometric mean was 964 orgs/100 ml, and the 2014 geometric mean was 345 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Twenty-one of the combined 24 samples (88%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if the geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should remain assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).

The Class B(WW2) aquatic life uses areassessed (monitored) as “fully supported.” This assessment was based on data collected in 2001 as part of the DNR/SHL stream biocriteria project and fish sampling data collected by the DNR Fisheries Bureau in 2013, 2014, 2015 and 2016. 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 Fisheries Bureau FIBI scores were76, 78 (both excellent) and 60,64 (both good). 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 now considered "monitored" because there were two or more samples (Fisheries Bureau FIBI samples) collected from this segment in multiple years over a recent five-year period (2012-2016).

Results of chemical/physical water quality monitoring from 2012 through 2014 do not suggest impairment of the Class B(WW2) aquatic life uses. Monitoring at station VRN-10 showed no violations of Class B(WW2) water quality criteria for ammonia (15 samples), dissolved oxygen (24 samples), pH (24 samples), temperature (23 samples), or chloride (19 samples). Thus, the Class B(WW2) aquatic life uses remain assessed(monitored) as “fully supported”.

Fish consumption uses are assessed (monitored) as “partially supported” based on results of U.S.EPA/DNR fish contaminant (RAFT) monitoring near the Volga State Recreation Area in 2001, 2005, 2007, 2008, 2012, and 2014. Results from these samplings have shown elevated levels of mercury in edible tissue of smallmouth bass 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. This advisory extends from the town of Volga upriver to the headwaters of the Volga River near Hawkeye in Fayette County and incudes the Little Volga River and 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. According to DNR’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 DNR/DPH advisory trigger level of 0.3 ppm for a one meal per week advisory. According to the DNR/DPH 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 DNR and DPH 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 0.241 ppm of mercury; the 2008 sample of smallmouth bass fillets contained 0.326. Because the level of mercury in the 2008 sample exceeded the DNR/DPH 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 0.158 to 0.274 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 was 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. The average level of mercury in tissue plugs from three smallmouth bass was 0.287 ppm (0.160-0.430). This level of mercury is sufficiently close to the advisory threshold of 0.3 ppm to justify continuing the existing consumption advisory and mercury impairment.