ADBNet

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 21 samples collected during the recreational seasons of 2012 through 2014 at UIRW Site 20 were as follows: the 2012 geometric mean was 346 orgs/100 ml, the 2013 geometric mean was 207 orgs/100 ml, and the 2014 geometric mean was 389 orgs/100 ml. All three geometric means slightly exceeded the Class A1 geometric mean criterion. Thirteen of the 21 samples (62%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if a recreation season geometric mean is greater than the water quality criterion of 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).

The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supported” based on biological data collected in 2011 and 2015 as part of the DNR/SHL stream biocriteria project. A series of biological metrics which 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 2015 FIBI score was 81 (excellent) and the BMIBI score was 78 (excellent). The 2011 FIBI score was 75(excellent) and the BMIBI score was 79 (excellent). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61. This segment passed the FIBI and BMIBI BICs 2/2 times in the last six years.

This aquatic life assessment is considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in a six year period (2011-2016). The assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).

Monitoring from 2012 to 2014 at Upper Iowa River Watershed Site 20 included analysis for ammonia, pH, and temperature. Of the 14 samples analyzed for ammonia, 13 samples contained less than the limit of detection (0.05 mg/l); the one detected sample contained 0.06 mg/l of ammonia. This level is well below any Class B(WW1) aquatic life criterion for ammonia. Similarly there were no violations of Class B(WW1) criteria in the 14 samples analyzed for pH and temperature. These results do not suggest impairment of the Class B(WW1) aquatic life uses.

Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this assessment segment.