Assessment Comments
Assessment is based on: (1) the results of monthly monitoring from January 2006 through December 2008 at the IDNR/UHL ambient city monitoring station located at the Highway 30 bridge downstream from Cedar Rapids (station 10570001) and (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2006.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria that violate state water quality criteria. The Class B(WW1) aquatic life uses are assessed (monitored) as "fully supported” based on results of ambient chemical/physical water quality monitoring. Fish consumption uses are assessed (monitored) as “fully supported” based on results of fish contaminant monitoring in 2006. The sources of data for this assessment include (1) the results of monthly monitoring from January 2006 through December 2008 at the IDNR/UHL ambient city monitoring station located at the Highway 30 bridge downstream from Cedar Rapids (station 10570001) and (2) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2006. This is the same assessment as that developed for the adjacent downstream segment of the Cedar River (IA 02-CED-0020-3).
Note: A TMDL for indicator bacteria in this segment of Cedar River was prepared and approved by EPA in February 2010. The approval of this TMDL moves the bacterial impairment for this segment from Iowa's list of Section 303(d) waters (Category 5a of the Integrated Report) to IR Category 4a (impaired; TMDL not required).
EXPLANATION: The Class A1 uses are assessed as "not supported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the 22 samples collected (363 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Ten of the 22 samples (45%) 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 IDNR’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 are "not supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
The Class B(WW1) aquatic life uses are assessed as "fully supported " based on results of monitoring from the IDNR/UHL ambient station at Highway 30 from 2006 through 2008. Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the approximately 33 samples collected. None of the five samples analyzed for toxic metals exceeded the relevant Class B(WW1) criteria.
Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Cedar Rapids in 2006. 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. The composite samples of fillets from channel catfish and freshwater drum had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0803 ppm; total PCBs: 0.091 ppm; and technical chlordane: 0.03 ppm. Levels of primary contaminants in the composite sample of freshwater drum fillets were as follows: mercury: 0.104 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.03 ppm. All levels of these contaminants from this monitoring are below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses in this segment of the Cedar River.
