Note: A TMDL for indicator bacteria in this segment of Black Hawk Creek was prepared by DNR and approved by EPA in 2006. Because all Section 303(d) impairments identified for the 2008 assessment/listing cycle (indicator bacteria) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved) of the current Integrated Report.

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 station 10070004 at Waterloo were as follows: the 2014 geometric mean was 99 orgs/100 ml, the 2015 geometric mean was 415 orgs/100 ml, and the 2016 geometric mean was 358 orgs/100 ml. Two of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Ten of the combined 24 samples (42%) 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 (monitored) as "fully supported" based on results of monitoring from the DNR/UHL ambient station SW of Waterloo (STORET Station 10070004) from 2012 through 2014. Monitoring at this station showed no violations of Class B(WW1) water quality criteria for dissolved oxygen, pH, temperature, ammonia-nitrogen, chloride, or sulfate in the 36 monthly samples analyzed during the 2012-2014 monitoring period. These monitoring results suggest that the Class B(WW2) aquatic life uses should be assessed as “fully supporting”.

Fish consumption uses are considered not assessed do to the age of the data. The previous assessment was (evaluated) as “fully supported” based on results of U.S.EPA/DNR fish contaminant (RAFT) monitoring near Hudson in 2004. The composite samples of fillets from channel catfish and smallmouth bass had very low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.072 ppm; total PCBs: 0.092 ppm; and technical chlordane: 0.044 ppm. Levels of primary contaminants in the composite sample of smallmouth bass fillets were as follows: mercury: 0.098 ppm; total PCBs: 0.09 ppm; and technical chlordane: < 0.03 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. The levels of contaminants do not exceed any of the Iowa advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory.