Des Moines River IA 04-UDM-1214

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 36 samples collected during the recreational seasons of 2012 through 2014 at ISU/ACOE Station 1 North West of Boone were as follows: the 2012 geometric mean was 60 orgs/100 ml, the 2013 geometric mean was 119 orgs/100 ml, and the 2014 geometric mean was 62 orgs/100 ml.  None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml.  Seven of the combined 36 samples (19) 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 IDNR’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).   Also, if significantly more than 10% of the samples exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A1 uses should be assessed as "partially supported." This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35 of U.S. EPA 1997b). All geometric means for the recreation seasons of 2012-2014 at ISU/ACOE Station 1 North West of Boone are below the geometric mean criterion. The percentage of violations of Iowa’s single-sample maximum criterion for E. coli (235 orgs/100 ml), however, is significantly greater than 10%. Thus, the primary contact recreation uses are assessed as "partially supported."

Results of chemical/physical water quality monitoring at ISU/ACOE Station 1 North West of Boone also/ however/ suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 65 Ammonia samples (maximum = 1.2 mg/L), 65 Dissolved Oxygen samples (minimum = 5.4 mg/L), 65 pH samples (range = 7.2 to 8.7), 65 Temperature samples (maximum = 28° c), 65 Chloride samples (maximum = 119.7 mg/L), or 65 Sulfate samples (maximum = 159 mg/L) occurred during monitoring from January 2012 to December 2014. None of the 12 samples analyzed for chloride and sulfate exceeded their respective criteria. None of the 10 samples analyzed during this period for toxic metals (e.g., cadmium, copper, mercury, and lead) violated the respective Class B(WW1) criteria. 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.

In agreement with the water quality results, the evaluated biological assessment based on data collected in 2010 as part of the IDNR Fisheries Bureau sampling project also suggests the aquatic life uses should be assessed as "fully supporting". A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2010 FIBI scores were 52 and 55 (both good). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI scores with biological impairment criteria (BIC) established from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32. This assessment is considered evaluated because the drainage area (5482 and 5560 mi2) above the sampling sites 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), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment doesn’t fall in the calibrated watershed size.

Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring at the Des Moines River near Boone in 2009. The composite samples of fillets from common carp and walleye had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.2 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The level of mercury in the composite sample of walleye fillets was 0.181 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 2009 RAFT sampling conducted at this river 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. In addition, results of water quality monitoring show that none of the toxic metals analyzed (e.g., cadmium, copper, and mercury) exceeded their respective Human Health (fish) water quality criteria.