ADBNet

[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).]

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 23 samples collected during the recreational seasons of 2014 through 2016 at Station 10570001 Cedar River Downstream of Cedar Rapids (DS1) were as follows: the 2014 geometric mean was 131 orgs/100 ml, the 2015 geometric mean was 277 orgs/100 ml, and the 2016 geometric mean was 233 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Ten of the combined 23 samples (43%) 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 Iowa 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 10570001 Cedar River Downstream of Cedar Rapids (DS1) suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW1) water quality criteria for 34 Ammonia samples (maximum = 1.3 mg/L), 35 Dissolved Oxygen samples (minimum = 7.6 mg/L), 34 pH samples (range = 7.4 to 8.7), 35 Temperature samples (maximum = 26.5°C), 35 Chloride samples (maximum = 59 mg/L), or 35 Sulfate samples (maximum = 69 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.

However, the results DNR/SHL stream REMAP biological sampling in 2005 indicate that the Class B(WW1) aquatic life uses should be assessed as "partially supporting". The evaluated biological assessment was based on data collected in 2005 as part of the DNR/SHL stream REMAP project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2005 FIBI scores were 49, 46 (fair) and the BMIBI scores were 19 (poor) and 47 (fair). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 0/2 times in the last 12years. This assessment is considered evaluated because the drainage area (6829 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC and failed to meet the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn't fall in the calibrated watershed size.

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/DNR fish contaminant (RAFT) monitoring at Cedar Rapids in 2015 and 2016. 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 2015 composite samples of fillets from channel catfish had an elevated level of total PCBs (0.26 ppm) but low levels of mercury (0.09 ppm) and technical chlordane (<0.02 ppm). The 2015 tissue plug largemouth bass samples analyzed for mercury were very low (average = <0.05 ppm). Follow-up sampling in 2016 indicated the total PCBs levels were below advisory trigger levels. Levels of primary contaminants in the 2016 composite sample of channel catfish fillets were as follows: mercury: 0.12 ppm; total PCBs: <0.06 ppm; and technical chlordane: <0.02 ppm. All levels of these contaminants from the 2016 monitoring are below advisory trigger levels, thus suggesting the continued “full support” of fish consumption uses in this segment of the Cedar River.