ThepresumptiveClass A1 (primary contact recreation) uses are assessed (monitored) as "not 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 DNR station 10910003 near Ackworth were as follows: the 2014 geometric mean was 1576 orgs/100 ml, the 2015 geometric mean was 503 orgs/100 ml, and the 2016 geometric mean was 1049 orgs/100 ml. All three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Seventeen of the combined 24 samples (71%) 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 "not supported."

Results of chemical/physical water quality monitoring at DNR station 10910003 near Ackworth suggest “full support” of the aquatic life uses. Monitoring showedno violations of Class B(WW2) water quality criteria for 35 Ammonia samples (maximum = 0.8 mg/L), 35 pH samples (range = 6.9 to 8.4), 36 Temperature samples (maximum = 30.4° c), 36 Chloride samples (maximum = 20 mg/L), or 36 Sulfate samples (maximum = 68 mg/L) occurred during monitoring from January 2014 to December 2016.1 of the 36 samples (3%) analyzed for Dissolved Oxygen (minimum = 3.2 mg/L) violated the Class B(WW2) 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(WW2) aquatic life uses.

In agreement with the water quality results, the (evaluated) assessment of the Class B(WW2) aquatic life uses based on data collected in 2015 as part of the DNR/SHL ambient site sampling project also indicates "full support". 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 2015 fish sample was not collected and the BMIBI score was 51 (fair). 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 1994-2008. The BMIBI BIC for this ecoregion is 51.

This aquatic life assessment is considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR requires a segment have two or more biological samples collected from the segment in multiple years in a five-year period to be considered “monitored”. This segment had a single sample collected in 2015.