Even though levels of indicator bacteria were very low during the 2012-2014 assessment period, the Class A1 (primary contact recreation) are assessed as "partially supported" based on levels of indicator bacteria that slightly exceeded state water quality criteria.  The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2012 through 2014 at IDNR ambient station near DeWitt were as follows:  the 2012 geometric mean was 75 orgs/100 ml, the 2013 geometric mean was 73 orgs/100 ml and the 2014 geometric mean was 116 orgs/100 ml.  All three geometric means are below and fully meet the Class A1 criterion of 126 orgs/100 ml.  Six of the 24 samples (25%) 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 recreation season geometric means are below Iowa’s water quality criterion, but the percentage of samples exceeding Iowa’s single-sample maximum criterion is significantly greater than 10%, the contact recreation uses should be assessed as "partially supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Thus, because the frequency of violations of Iowa’s Class A1 single-sample criterion for indicator bacteria is significantly greater than 10%, the Class A1 uses are assessed as “partially supported”

The geometric means of indicator bacteria (E. coli) in the 23 samples collected during the recreational seasons of 2012 through 2014 at the USGS station near DeWitt were similarly low:  the 2012 geometric mean was 64 orgs/100 ml, the 2013 geometric mean was 101 orgs/100 ml, and the 2014 geometric mean was 56 orgs/100 ml.  Similar to the results from IDNR ambient station at DeWitt, all three geometric means were below and fully met the Class A1 criterion of 126 orgs/100 ml.  Only three of the 19 samples (16%) 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, these results, with all geometric means below the Class A1 geometric mean criterion, and with a violation frequency of the single-sample maximum criterion that was not significantly greater than 10%, suggest “fully support” of the Class A1 primary contact recreation uses (see pgs 3-33 to 3-35 of U.S. EPA 1997b).  Due, however, to the violation frequency of the single-sample maximum criterion in the results of IDNR monitoring, the Class A1 uses are assessed as impaired (“partially supporting”). 

Based on the water quality sampling in this segment, the Class B(WW1) aquatic life uses should be assessed (monitored) as "fully supported" due to the lack of violations during the 2012-2014 monitoring period of Iowa Class B(WW1) water quality criteria for dissolved oxygen and ammonia-nitrogen in (1) the approximately 36 samples collected from at the IDNR fixed ambient station at DeWitt, (2) in the approximately 30 samples from the USGS ambient monitoring station at DeWitt, and (3) in the 42 samples collected by the LTRM program near the mouth of the Wapsipinicon River.  None of the 36 samples analyzed for chloride and sulfate and the IDNR ambient station exceed the respective Class B(WW1) aquatic life criteria. 

The only violations of a Class B(WW1) criterion in monitoring results from the three networks (IDNR, USGS, and LTRM) during the 2012-2014 period was for pH.  Two of the 42 LTRM samples (5%) exceeded the high pH criterion of 9.0 pH units, and one of 35 IDNR samples exceeded this criterion.  According to IDNR’s assessment methodology and U.S. EPA’s assessment guidelines (U.S. EPA 1997b, page 3-17), however, a violation frequency of less than 10% for conventional parameters such as pH does not suggest impairment of aquatic life uses.  Thus, the violation frequencies for pH (3% and 5%) do not suggest impairment of the aquatic life uses.  In addition, no violations of Class B(WW1) water quality criteria for the pesticides DDT, dieldrin, or chlorpyrifos occurred during the 2012-2014 period in the 32 samples from the USGS ambient monitoring station at DeWitt. 

In contrast to the water quality aquatic life assessment, the aquatic life assessment based on biological sampling suggests the aquatic life uses are "partially supporting" (IR 3b-u).  This evaluated biological assessment was based on data collected in 2011 - 2014 as part of the IDNR/SHL large river sampling project.  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 collected in the stream sampling reach.  The biological metrics were combined a benthic macroinvertebrate index (BMIBI).  The index rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).  The 2011 - 2014 BMIBI scores were 18, 22, 28 (all poor) and 56 (good).  The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the 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 BMIBI BIC for this ecoregion is 51.  This assessment is considered evaluated because the drainage area (2334 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 failed the BMIBI BIC (t1/4), 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..  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). 

Fish consumption uses remain assessed as "fully supported" based on results of the 2008, 2010, and 2014 EPA/IDNR or IDNR fish tissue sampling on the Wapsipinicon River north of McCausland.  This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of IDNR trend monitoring.  This site was scheduled for trend sampling in 2012, but drought-related low water conditions prevented sample collection.  The site was again sampled, however, for the 2014 trend sampling.  The results from the 2008 and 2010 samplings show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish samples of common carp.  In the 2008 samples, the levels were as follows: mercury: 0.0959 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.042 ppm.  In the 2010 sample, the levels of contaminants were as follows: mercury: 0.0768 ppm; total PCBs: 0.09 ppm; and technical chlordane: 0.052 ppm.  In the 2014 sample, the levels of contaminants were as follows: mercury: 0.1 ppm; total PCBs:  <0.24 ppm; and technical chlordane: 0.11 ppm.  [Note:  the high non-detect levels for total PCBs (0.24 ppm), which is above the 1 meal/week consumption advisory threshold of 0.2ppm, resulted from high detection level (0.08 ppm) for the individual Aroclors (1248, 1254, and 1260).  PCBs were reported as less than detection (<0.08 ppm) for all three Aroclors in this 2014 trend sample.]  The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.  The fish contaminant data generated from the 2008, 2010, and 2014 fish tissue samplings 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.