North Bear Creek IA 01-UIA-255

The Class A1 (primary contact recreation) uses remain assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria while the Class A2 (secondary contact recreation) uses are assessed as "fully supported". The geometric means of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2012 through 2014 at UIRW site 24 were as follows: the 2012 geometric mean was 35 orgs/100 ml, the 2013 geometric mean was 149 orgs/100 ml, and the 2014 geometric mean was 81 orgs/100 ml. One of the three geometric means (149 orgs/100 ml in 2013) very slightly exceeds the Class A1 criterion of 126 orgs/100 ml; the 2012 and 2014 geometric means are far below the Class A1 criterion of 126 orgs/100 ml. All three geometric means are well below the Class A2 geometric mean criterion of 630 orgs/100 ml. Four of the 20 samples (20%) exceeded the Class A1 single-sample maximum criterion of 235 orgs/100 ml; only one of the 20 samples (5%) exceeded the Class A2 single-sample maximum criterion of 2,880 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’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). Although the data suggest a Section 303(d) impairment of the Class A1 uses, the bacteria levels in this stream segment are very low relative to other streams in Iowa.

The Class B(CW1) aquatic life uses remain assessed (evaluated) as “fully supporting” based on data collected in 2000 and 2007 as part of the DNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2000 CBI score was 59.4 and the 2007 CBI score was 60. In addition, this site had two CW fish species comprising ~70% of the fish collected during both samplings. The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the CBI scores with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 2/2 times in the previous 17-year period (2000-2016). DNR analyzed the all the benthic macroinvertebrate and fish data from this site to make the determination that it passed the criteria. 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 17-year period (2000-2016); however, the multiple samples were not collected a five-year period.

Results of water quality monitoring at Site 24 of the Upper Iowa River Watershed (UIRW) project also suggest “full support” of the Class B(CW1) uses. Monitoring from 2012 to 2014 at this monitoring station included analysis of 14 samples for ammonia, temperature, and pH. None of these samples collected violated the respective Class B(CW1) criteria for ammonia, pH, or temperature.

In addition to the biological sampling, an updated summary of trout reproduction in Iowa streams was prepared by the DNR Fisheries Bureau in January 2019. This summary suggests that the Class B(CW1) aquatic life uses are also assessed as "fully supported". According to the updated summary, North Bear Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the DNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams (a Category I stream) that exhibit fairly consistent natural reproduction and maintain a viable population of brown trout without any stocking (6 miles of the 6.3 mile segment has natural reproduction of brown trout). This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.