Tipton Creek IA 02-IOW-755
from confluence with unnamed tributary (SE 1/4 S17 T87N R21W Hardin Co.) to confluence with New York Branch in S32 T88N R22W Hardin Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 9/13/2016 1:20:13 PM
- Updated
- 10/11/2016 9:46:12 AM
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" (IR 5p) due to levels of indicator bacteria that violate state water quality criteria. The source of data for this assessment is the results of monitoring from April 2007 through October 2008 conducted by the National Laboratory for Agriculture and the Environment (NLAE), Ames, IA, at station TC313 approximately 3 miles SW of Buckeye in Hardin County. The Class B(WW2) aquatic life uses are considered “not assessed” (IR 3a) due to the age of the biological data (>10 years) that were previously used to assess the aquatic life uses of this stream segment.
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on results of ambient monitoring for indicator bacteria (E. coli). The following table summarized recreation season geometric means of E. coli at station TC313 over the 2010-2014 period. Summary of recreation season (March 15-November 15) geometric means of indicator bacteria (E. coli) at station TC313 on Tipton Creek approximately 3 miles SW of Buckeye in Hardin County. Geometric means are number of organisms per 100 ml. Station: 2010 2011 2012 2013 2014 No. samples, 2010-14 No. > 235, 2010-14 % of samples > 235 TC313 143.0 135.8 218.2 35.1 84.7 37 12 32.4% The geometric means for the 2010, 2011, and 2012 recreation seasons all slightly exceeded the Class A1 criterion of 126 orgs/100 ml. The 2013 and 2014 geometric means, however, were well below (met) the Class A1 standard. Twelve of the 37 samples (32.4%) collected over the 2010-2014 period exceeded the single-sample maximum criterion of 235 E. coli organisms/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and according to IDNR’s assessment/listing methodology, if the geometric mean level of E. coli is greater than the state criterion of 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35of U.S. EPA 1997b). For previous assessments, results of biological sampling conducted in 1999 as part of the IDNR/SHL stream biocriteria project were used to assess the aquatic life uses of this stream as “fully supported”. As both chemical and biological water quality data age, however, they are less able to represent current water quality conditions. As data age beyond ten years, their ability to represent current water quality conditions is increasing suspect. Thus, because the biological data collected in 1999 are well over 10 years old, these data are not being used for the current assessment, and thus the Class B(WW2) aquatic life uses are now considered “not assessed”. Additional monitoring is needed in this assessment segment to update status of its aquatic communities.