North Raccoon River IA 04-RAC-1131

[Note 1: This assessment is also used, in part, for the adjacent upstream segment (IA 04-RAC-1132).]

[Note 2: A TMDL for pathogen indicator (E. coli) impairments in the Raccoon River basin was prepared by DNR and approved by EPA in June 2008. Because this TMDL covers the primary Section 303(d) impairment identified for the 2006 assessment/listing cycle, this waterbody was moved from IR Category 5a from the 2006 assessment/listing cycle to IR Category 4a (impaired; TMDL approved) for the 2008 cycle. This waterbody remains in IR Category 4a for the current cycle.]

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 24 samples collected during the recreational seasons of 2014 through 2016 at DNR station 10810001 near (downstream from) Sac City were as follows: the 2014 geometric mean was 292 orgs/100 ml, the 2015 geometric mean was 256 orgs/100 ml, and the 2016 geometric mean was 632 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Twelve of the combined 24 samples (50%) 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 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." Note: monitoring for indicator bacteria was not conducted at the USGS monitoring station during the 2012-2014 monitoring period.

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting” based on biological data collected in 2005 as part of the DNR/SHL stream REMAP biological monitoring project and 2013 as part of the DNR/SHL large river sampling project.. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were 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 score was 50 (fair) and 2005 BMIBI score was 48 (fair). The 2013 FIBI score was 48 (fair) and 2013 BMIBI score was 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 non-riffle FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This assessment is considered evaluated because the drainage area (829 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 (2/2) and failed the BMIBI BIC (0/2), 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. The results of this sampling thus do not meet DNR guidelines for developing a “monitored” assessment of support of the aquatic life uses that is appropriate to support addition of this waterbody to Iowa's Section 303(d) list. The assessment type for these waters will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to “monitored" (indicating an assessment with relatively high confidence). Such waters will be placed in either Category 2b or 3b of the IR and thus will be added to the state’s list of “waters in need of further investigation.”

Results of chemical/physical water quality monitoring at DNR station 10810001 near (downstream from) Sac City, however, suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.8 mg/L), 36 Dissolved Oxygen samples (minimum = 5.9 mg/L), 36 Temperature samples (maximum = 25.3° c), 36 Chloride samples (maximum = 93 mg/L), or 36 Sulfate samples (maximum = 220 mg/L) occurred during monitoring from January 2014 to December 2016.1 of the 35 samples (3%) analyzed for pH (range = 7.3 to 9.1) violated the Class B(WW1) criteria during the 2014-2016 monitoring period. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17) and Iowa DNR's assessment/listing methodology, a violation frequency of significantly greater than 10% for conventional parameters such as pH suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, these results do not suggest impairment of the Class B(WW1) aquatic life uses. Similarly, results of the 2012-2013 monitoring at USGS station 05482300 near Sac City did not show violation of Class B(WW1) criteria in the approximately 12 samples analyzed for ammonia, chloride, dissolved oxygen, pH, sulfate, and temperature. Thus, these results do not suggest impairment of the Class B(WW1) aquatic life uses.

Fish consumption uses are assessed (monitored) as “fully supported” based on results of DNR fish contaminant monitoring downstream from Sac City in 2012, 2014 and 2016. Although the composite samples of fillets from channel catfish collected in 2012 had low levels of contaminants, the average level of mercury in the tissue plug samples of walleye was slightly greater than threshold for a one meal per week consumption advisory. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.147 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm. The levels of contaminants in this sample are below the advisory thresholds for mercury (0.3 ppm), total PCBs (0.2 ppm) and chlordane (0.6 ppm). The average level of mercury in the tissue samples from four walleye, however, was 0.304 ppm (SD=0.045 ppm), thus slightly exceeding the one meal per week advisory threshold. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. According to the DNR/DPH advisory protocol, two consecutive samplings showing that contaminant levels are above the advisory threshold level are needed to justify issuance of a consumption advisory. Follow-up monitoring of levels of mercury in smallmouth bass was conducted in 2014 to determine whether a one-meal/week consumption advisory should be issued. The average level of mercury in the three smallmouth bass sampled was 0.160 ppm (SD= 0.105 ppm). Additional follow-up monitoring of levels of mercury in walleye was conducted in 2016 and the average level of mercury in the three walleye sampled was 0.250 ppm (SD= 0.036 ppm).These results suggest do not suggest the need for issuance of a one meal per week consumption advisory for predator fish in this river segment.