Raccoon River IA 04-RAC-1116

Note:  This assessment is also used for the adjacent upstream segment of the Raccoon River (IA 04-RAC-0010-2). 

Note:  A TMDL for nitrate and pathogen indicators (E. coli) was prepared by IDNR and approved by EPA in June 2008.  Because this TMDL covered the primary Section 303(d) impairments 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 river segment remains in IR Category 4a for the current cycle. 

EXPLANATION:  Results from the Des Moines Water Works, ISU/ACOE monitoring station located at Van Meter, and the IDNR/UHL station located upstream from Des Moines all suggest that Class A1 uses should be assessed as "partially supported" due to high levels of indicator bacteria.  The geometric means of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2012 through 2014 at IDNR station 10250002 upstream from Des Moines were as follows:  the 2012 geometric mean was 107 orgs/100 ml, the 2013 geometric mean was 142 orgs/100 ml, and the 2014 geometric mean was 930 orgs/100 ml.  All three geometric means exceeded the Class A1 criterion of 126 orgs/100 ml.  Nine of the 23 samples (39%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. 

The geometric means of indicator bacteria (E. coli) in the 36 samples collected during the recreational seasons of 2012 through 2014 at ISU/ACOE Station 10 upstream from Des Moines at Van Meter (STORET station 17250001) were as follows:  the 2012 geometric mean was 80 orgs/100 ml, the 2013 geometric mean was 449 orgs/100 ml, and the 2014 geometric mean was 491 orgs/100 ml.  Both the 2013 and 2014 geometric means exceed the Class A1 criterion of 126 orgs/100 ml.  Eighteen of the 36 samples (50%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. 

Similarly, results of bacterial monitoring by the Des Moines Water Works during recreational seasons of 2012 through 2014 also suggest that the Class A1 uses should be assessed as "partially supported.”  The geometric means of indicator bacteria (E. coli) in the 496 daily samples collected during the recreational seasons of 2012 through 2014 by the Des Moines Water Works were as follows:  the 2012 geometric mean was 112 orgs/100 ml, the 2013 geometric mean was 188 orgs/100 ml, and the 2014 geometric mean was 352 orgs/100 ml.  Similar to results of ISU/ACOE monitoring, the 2013 and 2014 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml.  Two hundred eighteen of the 496 samples (44%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml. 

According to U.S. EPA guidelines for Section 305(b) reporting and IDNR’s assessment/listing methodology, if a recreation season geometric mean exceeds the respective water quality criterion, the 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”.  Despite the ongoing impairment of the Class A1 uses, levels of indicator bacteria during the recreation seasons of 2012 through 2014 were relatively low. 

The Class B(WW1) aquatic life uses of this river segment are assessed as “fully supporting” based on results of chemical/physical water quality data.  At the IDNR/UHL city station at Van Meter, no violations of Class B(WW1) water quality criteria for dissolved oxygen, ammonia, pH, temperature, chloride, or sulfate occurred in the 33 samples collected during the 2012-2014 assessment period.  This lack of violations of Class B(WW1) criteria is consistent with the history of water quality monitoring in this segment and suggests that the aquatic life uses should be assessed (monitored) as “fully supported.” 

Similarly, no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen occurred in the 66 samples collected at the ISU/ACOE monitoring station during the 2012-2014 assessment period.  In addition, none of the 12 samples analyzed for toxic metals (lead, mercury, cadmium, and copper) exceeded their respective B(WW1) criteria 

Results of daily chemical/physical monitoring by the Des Moines Water Works during from 2012 through 2014 also suggest “full support” of the Class B(WW1) aquatic life uses.  No violations of Class B(WW1) criteria occurred for chloride (779 samples), sulfate (779 samples) or water temperature (253 samples).  Three of 754 samples (<1%) exceeded the Class B(WW1) criteria for pH.  According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b:  page 3-17), a violation frequency for conventional parameters such as pH of less than 10% does not suggest an impairment of aquatic life uses.  Thus, the results of Des Moines Water Works chemical/physical water quality monitoring from 2012-2014 also suggest “full support” of the Class B(WW1) aquatic life uses.

The Class C (drinking water) uses are assessed as "not supporting".  Levels of nitrate in this segment of the Raccoon River were higher and more typical during the 2012-2014 monitoirng period than during the previous (2010-2012) monitoring period.  Results of daily monitoring by the Des Moines Water Works in this river segment from 2012 through 2014 show that 27% of the daily samples collected (191 of 702 samples) contained nitrate above the 10 mg/l MCL (mean = 6.1 mg/l; median = 3.2 mg/l; maximum = 24.4 mg/l).  According to IDNR's assessment guidelines, the DMWW data suggest that the Class C drinking water uses should be assessed as "not supported". 

Results of ambient monitoring for nitrate conducted at Van Meter as part of the Iowa State University/Army Corps of Engineers network also show “nonsupport” of drinking water uses during the 2012-2014 period:  27% of the bi-monthly samples collected during the 2012-2014 assessment period (18 of 66 samples) exceeded the nitrate MCL (mean = 6.3 mg/l; median = 3.3 mg/l; maximum = 19.4 mg/l).  Results of IDNR/UHL ambient monthly monitoring for nitrate on the Raccoon River conducted upstream from Des Moines, however, show “full support” of drinking water uses:  only three of the 33 monthly samples (9%) collected during the 2012-2014 assessment period exceeded the nitrate MCL (mean = 4.8 mg/l; median = 3.1; maximum = 21.0 mg/l).  Despite the results of DNR monitoring that suggest “full support”, the more robust datasets from the ISU/ACOE and DMWW monitoring networks strongly suggest that the Class C (drinking water) uses should be assessed as impaired. 

Fish consumption/human-health uses remain assessed (monitored) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring at the Raccoon River near the Booneville access in 2010 and based on results of monitoring for toxics from 2012 to 2014.  The 2010 composite samples of fillets from common carp and flathead catfish had low levels of contaminants.  Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.105 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.  Levels of primary contaminants in the composite sample of flathead catfish fillets were as follows: mercury: 0.152 ppm.  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.  The fish contaminant data generated from the 2010 RAFT sampling conducted at this river segment show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody. 

Results of ISU/ACOE monitoring for mercury and copper in water do not suggest impairment of the fish consumption/human health use.  None of the 10 samples analyzed for the copper by ISU/ACOE during the 2012-2014 period exceeded the respective human-health/fish+water criteria.  Two of ten samples exceeded the Human Health/Fish+Water criterion of 0.05 ug/l for mercury.  The average level of mercury (0.036 ug/l) in the ten samples, however, was below the HH-FW criterion.  Thus, according to the Iowa DNR assessment/listing methodology, there results do not suggest impairment of the Human Health/Fish Consumption uses.