Steeles Branch IA 01-TRK-178
mouth (S26 T91N R4W Clayton Co.) to west line of S5 T90N R4W Delaware Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 7/18/2019 11:51:19 AM
- Updated
- 7/18/2019 11:55:26 AM
The presumptive Class A1 (primary contact recreation) uses and Class A2 (secondary contact recreation) uses remain assessed (monitored) as "not supported" due to levels of indicator bacteria that exceed water quality criteria. The Class B(CW1) aquatic life uses are considered “not assessed” due to lack of recent data upon which to base an assessment. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach. Sources of data for this assessment are the results of bacteria monitoring at two stations sampled during the 2012-2014 period: Steeles Branch 1 (STORET station 15220050) sampled from May 2012 to August 2014 and Steeles Branch 3 (STORET station 15280026) sampled from July 2012 to May 2014.
The Class A1 and A2 uses are assessed (monitored) as “not supported” due to levels of indicator bacteria (E. coli) that exceed the respective Class A1 and Class A2 geometric mean criteria. The geometric means of indicator bacteria (E. coli) in the 16 samples collected during the recreational seasons of 2012, 2013, and 2014 at Steeles Branch Site 1 were 1,232, 575, and 277 orgs/100 ml, respectively. The geometric means of indicator bacteria (E. coli) in the nine samples collected during the recreational seasons of 2012, 2013, and 2014 at Steeles Branch Site 3 were 2,866, 524, and 20 orgs/100 ml, respectively. Five of the six recreation season geometric means exceed Iowa’s Class A1 geometric mean criterion of 126 E. coli orgs/100 ml, and two of six also exceed the Class A2 geometric mean criterion of 630 E. coli orgs/100 ml, thus indicating nonsupport of both the Class A1 and A2 water contact recreation uses. Thirteen of the 16 samples (81%) at Steeles Branch Site 1 exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml, and five of nine samples (56%) exceeded this criterion at Steeles Branch Site 3. Compared to the Class A2 single sample maximum criterion of 2,880 orgs/100 ml, two of the 17 samples at Site 1 (12%) and one of the 10 samples at Site 3 (10%) exceeded this criterion. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if the geometric mean is greater than the respective criterion (126 orgs/100 ml for Class A1 and 630 orgs/100 ml for Class A2), the contact recreation uses are "not supported" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Class B(CW1) coldwater aquatic life and fish consumption (Class HH) uses remain "not assessed" due to the lack of water quality, biological or fish contaminant monitoring in this stream reach.