East Fork Des Moines River IA 04-EDM-971

Note:  A TMDL for indicator bacteria (E. coli) was prepared by IDNR and approved by EPA in January 2009.  Thus, the bacteria impairment for this segment was placed and remains in IR Category 4a (impaired; TMDL approved). 

EXPLANATION:  The Class A1 uses are assessed (monitored) as "partially supported" based on results of monitoring for indicator bacteria (E. coli).  The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2008 through 2010 at IDNR station 10550001 near St.  Joseph were as follows:  the 2012 geometric mean was 64 orgs/100 ml, the 2013 geometric mean was 394 orgs/100 ml, and the 2014 geometric mean was 231 orgs/100 ml.  The 2013 and 2014 geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml; the 2012 geometric mean is well-below the Class A1 criterion.  Ten of the 24 samples (42%) 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 “impaired” (partially supported).

Results of biological monitoring in 2002 and 2003 conducted as part of the DNR/UHL stream biocriteria/REMAP projects suggest that the Class B(WW1) aquatic life uses should be assessed (evaluated) as "fully supporting".  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 2003 FIBI score was 48 (fair) and the BMIBI score was 58 (good).   The 2002 BMIBI score was 66 (good).   The BMIBI average was 62.   The aquatic life use support was assessed (evaluated) as Fully Supporting (=FS), 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 1994-2004.   The non-riffle habitat 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 (925 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 both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.   

Results of IDNR/UHL ambient monitoring from 2012-2014 suggest relatively good water quality and “full support” of the Class B(WW1) uses.  None of the 36 samples collected during the 2012-2014 assessment period at the IDNR/UHL ambient monitoring station (10550001) violated Class B(WW1) water quality criteria for pH, ammonia-nitrogen, temperature, chloride, or sulfate.  One of the 36 samples (3%) had a level of dissolved oxygen (4.4 mg/l) that violated the Class B(WW1) criterion of 5.0 mg/l.  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 dissolved oxygen of less than 10% does not suggest an impairment of aquatic life uses.  Thus, the results of chemical/physical water quality monitoring from 2012-2014 suggest “full support” of the Class B(WW1) aquatic life uses.  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring near Algona in 2002 and 2008.  The composite samples of fillets from channel catfish and walleye in 2002 had low levels of contaminants.  Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.069 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.  Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.154 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.  Follow-up sampling of walleye was conducted in 2008.  The level of mercury in the composite sample of walleye fillets in 2008 was 0.14 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 2008 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.