West Fork Cedar River IA 02-WFC-801

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 24 samples collected during the recreational seasons of 2014 through 2016 at station 10070003 at Finchford were as follows: the 2014 geometric mean was 74 orgs/100 ml, the 2015 geometric mean was 168 orgs/100 ml, and the 2016 geometric mean was 146 orgs/100 ml. Two of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Seven of the combined 24 samples (29%) 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 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."

Results of chemical/physical water quality monitoring at station 10070003 at Finchford suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.1 mg/L), 36 Dissolved Oxygen samples (minimum = 6.4 mg/L), 35 pH samples (range = 7.6 to 8.5), 36 Temperature samples (maximum = 24.1° c), 36 Chloride samples (maximum = 21 mg/L), or 36 Sulfate samples (maximum = 48 mg/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.

According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/DNR fish contaminant (RAFT) monitoring near Allison, Iowa, in 2011 and 2012. In the 2011 samples, the composite samples of fillets from channel catfish had low levels of contaminants: mercury: 0.136 ppm; total PCBs: 0.091 ppm; and technical chlordane: <0.03 ppm. The average level of mercury in the tissue plugs from four smallmouth bass was 0.415 ppm (SD=0.099 ppm). This level of mercury exceeded Iowa's threshold for a one-meal per week consumption advisory of 0.3 ppm. According to Iowa’s fish consumption advisory protocol, however, two consecutive samplings that show contaminant levels above an advisory threshold are needed to confirm that an advisory should be issued. Thus, follow-up sampling was conducted in 2012. The results of this follow-up sampling showed that the average level of mercury in the tissue plugs from four smallmouth bass (0.182 ppm; SD=0.077 ppm) was well below the advisory threshold of 0.3 ppm, thus suggesting no justification for issuance of a consumption advisory for this river segment. These results suggest continued full support of the fish consumption uses.