South Bear Creek IA 01-UIA-252
confluence with N. Bear Cr. (S25 T100N R7W) to spring source (Mestad Spring) in S29 T100N R7W Winneshiek Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 7/25/2019 7:57:12 AM
- Updated
- 8/30/2019 7:12:37 AM
The presumptive Class A1 (primary contact recreation) uses remain assessed (monitored) as “partially supporting” due to levels of indicator bacteria that exceed water quality criteria.The presumptive Class A2 (secondary contact recreation) uses are assessed (monitored) as “fully supported”. The Class B(CW1) coldwater aquatic life uses are assessed (monitored) as "fully supported” based on 2012-2014 water quality results and on an updated summary of trout reproduction by the DNR Fisheries Bureau. Fish consumption (Class HH) uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment. The sources of data for this assessment are (1) the results of monitoring for water quality including indicator bacteria conducted at Site 23 of the Upper Iowa River Watershed (UIRW) project (STORET No. NEIARCD 191910014) from April 2012 through October 2014 and (2) the January 2019 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau.
The presumptive Class A1 (primary contact recreation) uses remain assessed as “partially supporting”. The geometric means of indicator bacteria (E. coli) in the 21 samples collected during the recreational seasons of 2012 through 2014 at UIRW Site 23 were as follows: the 2012 geometric mean was 50 orgs/100 ml, the 2013 geometric mean was 135 orgs/100 ml, and the 2014 geometric mean was 125 orgs/100 ml. Only the 2013 geometric mean exceeded the Class A1 criterion of 126 orgs/100 ml and then only very slightly (by 9 orgs/100 ml). Six of the 21 samples (29%) 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 DNR’s assessment/listing methodology, if a recreation season geometric means 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). All three geometric means met and were far below the Class A2 geometric mean criterion of 630 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if all recreation season geometric means meet the respective water quality criterion, the contact recreation uses are "fully supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Despite the new impairment of the Class A1 uses, this stream segment continues to show some of the lowest stream bacteria levels in the state of Iowa. Based on the 2012-2014 water quality results and 2019 updated DNR Fisheries trout reproduction data, the Class B(CW1) coldwater aquatic life uses remain assessed (monitored) as “fully supporting”. Results of water quality monitoring from 2012 to 2014 at Upper Iowa River Watershed Site 23 did not indicate impairment of the Class B(CW1) uses. Analysis of 14 samples for ammonia, temperature, and pH showed that none of the samples collected violated the respective Class B(CW1) criteria. The updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in January 2019 also suggests the Class B(CW1) uses are "fully supported". According to the updated summary, Bear Creek (aka South 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 that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population of Brown Trout at this time (a Category II stream).