[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 is placed in IR Category 4a (impaired; TMDL approved).]

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).

The Class B(WW1) aquatic life uses are assessed (evaluated) as “partially supporting” based on data collected in 2003 and 2011-2013 as part of the IDNR/SHL stream ambient biological and REMAP sampling projects. 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 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). The 2011-2013 BMIBI scores were 31, 43, 44 , 54 (all fair) and 57 (good). 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 biological data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 1/1 times in 2003 and passed the BMIBI BIC 0/5 times in the last five years. This assessment is considered evaluated because the drainage areas (977 and 927 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 segment passed the FIBI BIC (1/1) and failed the BMIBI BIC (0/5), it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the sites used for the assessment don’t fall in the calibrated watershed size. According to IDNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). IDNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

Despite the results of biological monitoring that suggest “partial support” of the Class B(WW1) aquatic life uses, the 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.