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 Otterville Access station were as follows: the 2014 geometric mean was 84 orgs/100 ml, the 2015 geometric mean was 57 orgs/100 ml, and the 2016 geometric mean was 194 orgs/100 ml. One of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Four of the combined 24 samples (17 %) 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 Iowa 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 Class B(WW1) (aquatic life) uses are assessed (evaluated) as "partially supported" based on results of DNR/SHLbiological sampling conducted from2012-2014 as part of the large river/stream nutrient sampling projects and on data collected in 2004 by the DNR Fisheries Bureau. 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 2004 FIBI score was 48 (fair). The2012, 2013 and 2014 BMIBI scores were 67 (good), 45 (fair) and 21 (poor). 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 FIBI BIC for this ecoregion is 44 and the artificial substrate BMIBI BIC for this ecoregion is 52. This assessment is considered evaluated because the drainage areas (905 and 909 mi2) above the sampling sites were greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the FIBI BIC in 2004 and failed the BMIBI BIC (1/3 times) in the last five years, 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.

Results of chemical/physical water quality monitoring at Otterville Access station, however, suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 35 Ammonia samples (maximum = 0.4 mg/L), 36 Dissolved Oxygen samples (minimum = 7.4 mg/L), 35 pH samples (range = 7.1 to 8.5), 36 Temperature samples (maximum = 26.1°C), 36 Chloride samples (maximum = 29 mg/L), or 36 Sulfate samples (maximum = 36 mg/L) occurred during monitoring from January 2014 to December 2016. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

The fish consumption uses remain “not assessed” due to the lack of recent fish tissue monitoring in this river segment.