The Class A1 uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The geometric means of indicator bacteria (E. coli) in the 24 samples collected during the recreational seasons of 2012 through 2014 at IDNR station 10630001 and 10630003 were as follows: the 2012 geometric mean was 233 orgs/100 ml, the 2013 geometric mean was 107 orgs/100 ml, and the 2012 geometric mean was 294 orgs/100 ml. All three geometric means slightly exceed the Class A1 criterion of 126 orgs/100 ml. Eleven of the 24 samples (46%) 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 a recreation season geometric mean exceeds the respective water quality criterion, the 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”.

This monitored aquatic life assessment was based on data collected in 2012 and 2013 as part of the IDNR/SHL large river sampling project and on data collected in 1999 by the IDNR Fisheries Bureau. A series of biological metrics which 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 2012 BMIBI score was 13 (poor). The 2013 BMIBI scores were 48 and 51 (both fair). The 1999 Fisheries FIBI score was 15 (poor). The aquatic life use support was assessed 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 FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. The biological impairment criteria were determined from a statistical analysis of biological data collected at stream ecoregion reference sites from 1994-2008. This segment failed the FIBI BIC in 1999 and passed the BMIBI BIC 1/3 times in the last five years. This assessment is considered "monitored" because there were two or more samples collected from this segment in multiple years in a recent five year period.

In contrast to results of biological monitoring which suggest that aquatic life uses are "partially supported", results of ambient chemical/physical water quality suggest “full support” of the aquatic life uses. None of the 36 samples collected during the 2012-2014 assessment period at the IDNR monthly station violated Class B(WW1) water quality criteria for dissolved oxygen, pH, temperature, ammonia-nitrogen, chloride, or sulfate. Based, however, on results of the biological assessment (above), the aquatic life uses of this stream segment will remain assessed (monitored) as “partially supported” (IR Category 5b-v).

The occurrence of a fish kill at this segment in August 2010, also suggests the Class B(WW1) uses should be assessed as "partially supported." A fish kill occurred at this site on August 23, 2010. The kill was a result of a leak from an anhydrous ammonia tank pipe. The cloud was sprayed down with water by the fire department. A road culvert and a tile intake/line allowed the ammonia to reach Mill Branch Creek. Mill Branch Creek flows into Cotton Creek, which then flows into White Breast Creek. Dead fish were observed in all three of these streams below the tile line. The kill affected 10.5 miles of these streams. Approximately 2,784 fish were killed. No information on the species of fish killed was provided. The estimated value of these fish was $12,891.81. IDNR sought and received restitution for this fish kill.

According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant,” the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required). IDNR feels that (1) TMDLs should not be required for kills caused by a one-time illegal or unauthorized release of manure or other toxic substance where enforcement actions were taken and (2) enforcement action is more appropriate, efficient, and effective for addressing a spill-related impairment than is the TMDL process. Thus, this assessment segment was placed in Category 4d of Iowa’s 2012 Integrated Report where it remains.

Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this stream segment.