Dry Run IA 02-CED-6293
from confluence with unnamed tributary (center S23 T89N R14W Black Hawk Co.) to headwaters in SW1/4 S32 T89N R14W Black Hawk Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 8/17/2016 9:37:28 AM
- Updated
- 9/29/2016 10:37:37 AM
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported” (IR 5p) due to levels of indicator bacteria that exceed state water quality criteria. The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” (IR 2a) based on data collected from 2013 through 2014. The source of data for this assessment is the results of (1) chemical and physical monitoring conducted on Dry Run Creek from April 2013 through October 2014 at Site DRC-9 at Union Road (STORET station 15070006) and (2) bacteria monitoring at this station from October 2012 to October 2014.
The presumptive Class A1 (primary contact recreation) are assessed (monitored) as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 19 samples collected during the recreational seasons of 2012 through 2014 at Section 319 Site DRC-9 were as follows: the 2012 geometric mean was 310 orgs/100 ml, the 2013 geometric mean was 528 orgs/100 ml, and the 2014 geometric mean was 230 orgs/100 ml. All three geometric means exceed the Class A1 criterion of 126 orgs/100 ml. Twelve of the 19 samples (63%) 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 IDNR’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). Thus, because at least one recreation season geometric mean exceeded criteria for Class A1 uses, these uses are assessed as “impaired.”
The presumptive Class B(WW1) aquatic life uses remain assessed (monitored) as “fully supported” based on results of chemical/physical monitoring conducted for the Dry Run Creek Watershed project from 2013 through 2014. No violations of Class B(WW1) criterion for dissolved oxygen, temperature, pH or chloride occurred in the approximately 16 samples analyzed at station DRC-9 over this period. These data suggest a relatively stable headwater aquatic environment in terms of chemical/physical water quality, with pH values ranging only from 7.7 to 7.9 and the maximum temperature being only 17.9 C.