Bear Creek IA 02-CED-517

The presumptive Class A1 (primary contact recreation) uses are assessed (evaluated) 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 12 samples collected at station 15570007 during the recreational season of 2010 (903 orgs/100 ml), and the geometric mean of the 12 samples collected during the recreation season of 2011 (1,935 orgs/100 ml) both far exceeded the Class A1 criterion of 126 orgs/100 ml. All of the combined 24 samples (100%) exceeded Iowa’s 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).

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supporting” based on biological data collected in 2001, 2010 and 2013 as part of the DNR/SHL stream biocriteria project. The 2001 FIBI scores were 44 (fair) and 52 (good); the BMIBI scores were 73 (good) and 70 (good). The 2010 FIBI score was 64 (good) and the BMIBI score was 53 (fair). The 2013 FIBI score was 62 (good) and the BMIBI score was 56 (fair). The aquatic life use support was assessed (evaluated) as fully supported (=FS), 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 1994-2004. The non-riffle habitat FIBI BIC for this ecoregion is 44, the natural substrate BMIBI BIC (2001 and 2013 BMIBI samples) for this ecoregion is 70 and the artificial substrate BMIBI BIC for this ecoregion is 52 (2010 BMIBI sample). This segment passed the FIBI BIC 4/4 times and passed the BMIBI BIC 3/4times in the last 16 years.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 16 years (2001-2016); however, the multiple samples were not collected during a recent five-year period.

The results of ambient water quality monitoring at station 15570007 in 2010 and 2011 indicated good chemical water quality in this stream segment, are consistent with the results of biological monitoring, and thus suggest “full support” of the Class B(WW2) aquatic life uses. No violations of Class B(WW2) water quality criteria for dissolved oxygen, pH or temperature occurred in the 24 samples analyzed from May 2010 to July 2011.