Dry Run (South Branch) IA 02-CED-2062
mouth (T89N R14W Sec13) to headwaters (T88N R14W Sec9)
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 8/17/2016 8:58:18 AM
- Updated
- 9/29/2016 9:14:35 AM
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not 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 results of chemical/physical monitoring in 2013 and 2014. The sources of data for this assessment include (1) the results of chemical and physical water quality monitoring conducted on Dry Run Creek from April 2013 through October 2014 at three stations sampled as part of the Dry Run Creek Watershed Project: Site DRC5 at University Avenue (STORET station 15070003), at Site DRC8 at Greenhill Road (STORET station 15070005), and Site DRC10 at Viking Road (STORET station 15070007) and (2) the results of Section 319 bacterial monitoring from August 2012 through October 2014 at these three stations: DRC-5, DRC-10, and DRC-8.
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "not supported" due to violations of Iowa’s water quality criteria for indicator bacteria. The geometric means of indicator bacteria (E. coli) in the samples collected at each station (total N=59 samples) during the recreational seasons of 2012, 2013, and 2014, respectively, at each of the three Section 319 monitoring stations in this assessment segment were as follows:
1. DRC-10 (15070007), 19 samples: geometric means were 509, 456, and 606 orgs/100 ml;
2. DRC-5 (15070003), 23 samples: geometric means were 833, 731, and 665 orgs/100 ml;
3. DRC-8 (15070005), 17 samples: geometric means were 544, 475, 62 orgs/100 ml.
From 59 to 74% of the samples at each of the Section 319 sites 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 the geometric mean 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).
The presumptive Class B(WW1) aquatic life uses are assessed (monitored) as “fully supported” based on results of chemical/physical monitoring conducted for the Dry Run Creek Watershed project from April 2013 through October 2014. No violations of Class B(WW1) criterion for ammonia, dissolved oxygen, temperature, pH, or chloride occurred in the approximately 17 samples analyzed at each station over this period.