Assessment Comments
Assessment is based on: (1) the results of monthly monitoring from January 2004 through December 2006 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 2004 through December 2006 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).
EXPLANATION: The Class A1 uses were assessed as "not supported" based on results of ambient monitoring for indicator bacteria (E. coli). Due to recent changes in Iowa’s Water Quality Standards, Iowa’s assessment methodology for indicator bacteria has changed. Prior to 2003, the Iowa WQ Standards contained a high-flow exemption for the Class A criterion for indicator bacteria (fecal coliforms) designed to protect primary contact recreation uses: the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) did not apply "when the waters [were] materially affected by surface runoff." Due to a change in the Standards in July 2003, E. coli is now the indicator bacterium, and the high flow exemption was eliminated and replaced with language stating that the Class A criteria for E. coli apply when Class A1, A2, or A3 uses “can reasonably be expected to occur.” Because the IDNR Technical Advisory Committee on WQ Standards could not agree on what flow conditions would define periods when uses would not be reasonably expected to occur, all monitoring data generated for E. coli during the assessment period, regardless of flow conditions during sample collection, will be considered for determining support of Class A uses for purposes of Section 305(b) assessments and Section 303(d) listings.
The geometric mean level of indicator bacteria (E. coli) in the 71 samples collected (173 orgs/100ml) exceeds the Iowa Class A1 water quality criterion of 126 orgs/100ml. Twenty-seven of the 71 samples (38%) 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). sample maximum criterionsample maximum criterionsample maximum criterionThese results are very similar to those from the previous (2006) assessment cycle: the geometric mean in the 39 samples collected between 2002-2004 was 172 orgs/100 ml; 13 of the 39 samples (33%) exceeded the single-sample maximum criterion of 235 orgs/100 ml. Taken together, the results from the 2006 and 2008 assessment cycles suggest relatively constant, and generally low, levels of indicator bacteria in this segment of the Cedar River.
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 2004 through 2006. Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the approximately 34 samples collected. None of the 14 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. Prior to 2006, IDNR used action levels published by the U.S. Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest impairment of the fish consumption uses. This scenario does not apply to the fish contaminant data generated from the 2006 RAFT sampling in this assessment segment.
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.
