Cedar River IA 02-CED-455
from Prairie Cr. (SE 1/4 S34 T83N R7W Linn Co.) to confluence with McCloud Run in SW 1/4 S16 T83N R7W Linn Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 8/8/2016 3:38:37 PM
- Updated
- 8/8/2016 3:38:56 PM
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" (IR 4a) due to levels of indicator bacteria that very slightly exceed state water quality criteria. Results of ambient chemical/physical water quality monitoring suggest that the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported.” However, the Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting” (IR 3b-u) based on the 2005 IDNR/SHL stream REMAP biological sampling in 2005 near Bertram. Fish consumption uses remain assessed (monitored) as “fully supported” (IR 2a) 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 2012 through December 2014 at the IDNR/UHL ambient city monitoring station located at the Highway 30 bridge downstream from Cedar Rapids (station 10570001), (2) IDNR/SHL stream REMAP biological sampling in 2005 near Bertram, and (3) results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring in 2006.
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 moved 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). Results of monitoring from the IDNR/SHL ambient station downstream from Cedar Rapids from 2012 through 2014 suggest "full support" of the Class B(WW1) aquatic life uses. Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, ammonia-nitrogen, or chloride/sulfate in the approximately 35 samples collected. During the assessment period, one of 34 samples (3%) contained a level of pH that violated the Class B(WW1) criterion of 9.0 pH units: According to U.S. EPA assessment guidelines, if less than 10% of samples exceed state criteria for pH, the primary contact (Class A) and aquatic life (Class B) uses should be assessed as fully supported (see pgs 3-17 of U.S. EPA 1997b). Violations of pH in ambient waters tend to reflect high levels of primary productivity and do not typically reflect the addition of pollutants to surface waters.
EXPLANATION: The Class A1 uses are assessed as "partially supported" based on results of monitoring for indicator bacteria (E. coli). The geometric mean level of indicator bacteria (E. coli) in the 23 samples collected during the recreation seasons of 2012 through 2014 are as follow: the 2012 geometric mean was 56 orgs/100 ml, the 2013 geometric mean was 48 orgs/100 ml, and the 2014 geometric mean was 131 orgs/100 ml. Only the 2014 geometric mean exceeded—and then only very slightly—the Class A1 geometric mean criterion of 126 orgs/100 ml. Three of the 23 samples (13%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. Only the 2014 geometric mean suggests impairment of the Class A1 uses. These monitoring results indicate exceptionally low levels of indicator bacteria in this segment of the Cedar River. 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 should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b). Thus, the Class A1 uses are assessed as “partially supported”. Despite the ongoing impairment of the Class A1 uses in this river segment, levels of indicator bacteria are very low.
Fish consumption uses remain 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.