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 24 samples collected during the recreational seasons of 2014 through 2016 at Little Sioux River near Milford (STORET station 10300001) were as follows: the 2014 geometric mean was 146 orgs/100 ml, the 2015 geometric mean was 212 orgs/100 ml, and the 2016 geometric mean was 255 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Twelve of the combined 24 samples (50%) 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 DNR’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). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as "partially supported."

The assessment of the Class B(WW1) aquatic life uses was based on data collected in 2011 and 2014 as part of the DNR/SHL stream biocriteria project. The 2011 FIBI score was 60 (good) and the BMIBI score was 54 (fair). The 2014 FIBI score was 41(fair) and the BMIBI score was 50 (fair). 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 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 riffle site FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 1/2 times and passed the BMIBI BIC 0/2 times in the last six years.

This assessment is considered "evaluated" because even though there were multiple samples collected in multiple years in a five year period, one of those samples is now greater than five years old (2011 sample). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s Section 303(d) list of impaired waters. Additional monitoring is needed in this assessment segment to update status of its aquatic communities.

Results of chemical/physical water quality monitoring at Little Sioux River near Milford (STORET station 10300001) suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 36 Ammonia samples (maximum = 1.4 mg/L), 36 pH samples (range = 7.3 to 8.8), 36 Temperature samples (maximum = 26.7 °C), 36 Chloride samples (maximum = 43 mg/L), or 36 Sulfate samples (maximum = 240 mg/L) occurred during monitoring from January 2014 to December 2016. One of the 36 samples (3%) analyzed for Dissolved Oxygen (minimum = 4.4 mg/L) violated the Class B(WW1) criteria during the 2014-2016 monitoring period. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17) and Iowa DNR's assessment/listing methodology, a violation frequency of significantly greater than 10% for conventional parameters such as Dissolved Oxygen suggests impairment of aquatic life uses. Because the frequency of violations for this parameter is not greater than 10 percent, 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 river segment.