Iowa River IA 02-IOW-621

The 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 18 samples collected during the recreational seasons of 2014 through 2016 at Iowa DNR station 10580003 Iowa River near Wapello were as follows: the 2014 geometric mean was 10 orgs/100 ml, the 2015 geometric mean was 80 orgs/100 ml, and the 2016 geometric mean was 202 orgs/100 ml. One of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Five of the combined 18 samples (28%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.Additionally, the geometric means of indicator bacteria (E. coli) in the 8 samples collected during the recreational seasons of 2014 through 2016 at USGS station 05465500 at Wapello were as follows: the 2014 geometric mean was 150 orgs/100 ml, the 2015 geometric mean was 6100 orgs/100 ml, and the 2016 geometric mean was 400 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.According to U.S. EPA guidelines for Section 305(b) reporting and Iowa DNR’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). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported."

Both results of chemical/physical water quality monitoring at Iowa DNR station 10580003 Iowa River near Wapello and at USGS station 05465500 at Wapello suggest “full support” of the aquatic life uses. Monitoring at Iowa DNR station 10580003 Iowa River near Wapello showed no violations of Class B(WW1) water quality criteria for 27 Ammonia samples (maximum = 0.2 mg/L), 27 Dissolved Oxygen samples (minimum = 6.9 mg/L), 27 pH samples (range = 7.2 to 8.9), 27 Temperature samples (maximum = 28.2°C), 27 Chloride samples (maximum = 42 mg/L), or 27 Sulfate samples (maximum = 44 mg/L) occurred during monitoring from October 2014 to December 2016. Monitoring at USGS station 05465500 at Wapello showed no violations of Class B(WW1) water quality criteria for 45 Ammonia samples (maximum = 1 mg/L), 43 Dissolved Oxygen samples (minimum = 6.1 mg/L), 45 pH samples (range = 7.3 to 9), 52 Temperature samples (maximum = 27.7°C), 45 Chloride samples (maximum = 74.3 mg/L), or 45 Sulfate samples (maximum = 65.6 mg/L) occurred during monitoring from January 2014 to December 2016.Additionally, Monitoring at USGS station 05465500 at Wapello showed no violations of Class B(WW1) toxics (acute or chronic) water quality criteria 45 Arsenic samples (maximum = 2.1 ug/L) and 45 Selenium samples (maximum = 2.2 ug/L) occurred during monitoring from January 2014 to December 2016. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

Results of Class HH (human health) monitoring at USGS station 05465500 at Wapello suggest “full support” of the human health uses. Monitoring showed no violations of Class HH (human health) criteria for 45 Arsenic samples (maximum = 2.1 ug/L), 1 Cadmium samples (maximum = 0.015 ug/L), 1 Chromium samples (maximum = 0.4 ug/L), 1 Copper samples (maximum = 0.84 ug/L), 1 Dieldrin samples (maximum = 0.004 ug/L), 1 Nickel samples (maximum = 2300 ug/L), 45 Selenium samples (maximum = 2.2 ug/L), 1 Zinc samples (maximum = 3.5 ug/L), or 1 p,p'-DDE samples (maximum = 0.0025 ug/L) occurred during monitoring from January 2014 to December 2016. According to Iowa DNR’s assessment/listing methodology, if the mean level of a toxic metal or pesticide is greater than its respective human health criterion, impairment (“non support”) of the Human Health use is indicated. Thus, these results thus suggest (“full support”) of the Class HH (human health) uses.

Despite the occasional report of a detectable level of dieldrin, results of fish contaminant sampling in this river segment have show very low levels of this now-banned pesticide. Levels of dieldrin in the 2007 composite sample of Common Carp fillets was 6 ppb of dieldrin. Levels in the composite sample of whole-fish common carp analyzed for the 2008 RAFT and were 60 ppb in the composite whole-fish Common Carp sample analyzed in 2014. Although Iowa does not have a consumption advisory trigger level for dieldrin, the levels seen in the 2007 fillet samples and the 2008 and 2014 whole-fish composite samples from Wapello are well below the Iowa’s previous advisory trigger of 300 ppb of dieldrin (i.e., the U.S. FDA action level for dieldrin). Levels of dieldrin in Iowa fish have declined significantly since the early and mid-1980s when levels of 300 ppb to 500 ppb were not uncommon. Due to the low levels of dieldrin in fish tissue samples from this river segment, and due to the low frequency of historic violations of the human health (fish + water) dieldrin criterion that occurred, this assessment is considered appropriate for Iowa’s IR Category 3b (potential impairment). IR Category 3b waters will be added to Iowa’s list of waters in need of further investigation.

Fish contaminant monitoring for toxic parameters other than dieldrin (e.g., mercury, PCBs, and chlordane) suggest “full support” of fish consumption uses. Fish consumption was conducted near Wapello in 2008, 2010, and 2014 as part of the EPA/DNR fish tissue program. This site has been sampled for whole-fish common carp since 1995 on an every-other-year basis as part of RAFT trend monitoring. The 2008 composite whole-fish samples of common carp contained the following levels of common contaminants: mercury: 0.135 ppm; total PCBs: 0.217 ppm; and technical chlordane: 0.067 ppm. Contaminant levels in the 2010 composite whole-fish sample of common carp had similar levels: mercury: 0.0614 ppm; total PCBs: 0.111 ppm; and technical chlordane: 0.091 ppm. The 2014 whole-fish Common Carp sample had similar levels of these contaminants: mercury 0.11 ppm; total PCBs: <0.24 ppm, and chlordane: 0.12 ppm. These results do not suggest the need for issuance of a consumption advisory.

Due, however, to the low frequency with which violations of the human health (fish + water) dieldrin criterion occurs, the assessment of the HH-fish consumption uses in this river segment is considered appropriate for Iowa’s IR Category 3b (potential impairment). IR Category 3b waters are added to Iowa’s list of waters in need of further investigation.