Little Cedar River IA 02-CED-574

The Class A1 uses remain assessed as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The overall geometric mean level of indicator bacteria (E. coli) in the 48 samples collected from April 2001 through (631 orgs/100ml) exceeded the Iowa Class A1 water quality criterion of 126 orgs/100ml. (Note: multiple samples were collected on selected sample dates during summer seasons; these multiple samples were averaged into a single daily value for purposes of developing this assessment.) Thirty-two of the 48 samples (67%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to DNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 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). Other approaches to summarizing the bacterial data for this station also suggest nonsupport of the Class A1 uses. For example, all yearly recreational season geometric means far exceed the Class A1 criterion of 126 orgs/100 ml: 2001: 8 samples with geometric mean of 269 orgs/100 ml; 2002: 16 samples with geometric mean of 644 orgs/100 ml; 2003: 10 samples with geometric mean of 530 orgs/100ml; 2004: 14 samples with geometric mean of 1,136 orgs/100 ml. Due to age of these data (greater than five years), the assessment type was changed from “monitored” (higher confidence assessment) to “evaluated” (lower confidence assessment). Despite the aging of the data upon which this assessment is based beyond 10 years, the assessment remains in IR Category 5a. Age of data is not a sufficient justification for removal of an impairment.

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supported” based on results of chemical/physical water quality monitoring conducted near Ionia in support of TMDL development from 2002 through 2004. The results of this monitoring showed no violations of Class B(WW1) criteria for dissolved oxygen or pH in the 41 samples collected, or for ammonia-nitrogen in the 32 samples collected and analyzed. The parameter coverage at this station was somewhat limited (i.e., no analysis for toxic metals or pesticides). This assessment was consistent with previous assessments of aquatic life uses (“fully supported”) based on results of DNR/SHL biocriteria sampling in 1995 and on results of DNR stream use assessments in 1995 (see assessment developed for the 2000 cycle). Due to age of these data (greater than five years), the assessment type was changed from “monitored” (higher confidence assessment) to “evaluated” (lower confidence assessment).

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of DNR fish contaminant monitoring at Chickasaw Park in 2015. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. Fish contaminant data generated from the 2003 RAFT sampling conducted in this assessment segment showed that levels of contaminants were sufficiently high for concern and thus justified follow-up monitoring. The levels of at least one contaminant from past monitoring at this station approached one or more advisory trigger levels, thus suggesting the need for additional (follow-up) monitoring to determine whether a consumption advisory should be issued.

The 2015 composite sample of fillets from golden redhorse and tissue plug samples from smallmouth bass had generally low levels of contaminants. Levels of primary contaminants in the composite sample of golden redhorse were as follows: mercury: 0.14 ppm; total PCBs: <0.06 ppm; and technical chlordane: <0.02 ppm. The average mercury concentration found in the tissue plug samples from five smallmouth bass fillets was 0.140 ppm (SD = 0.089). The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. Because levels of all these contaminants from the 2015 fish tissue monitoring are below Iowa’s advisory trigger levels, the fish consumption uses in this segment of the Little Cedar River are assessed as “fully supported.”