North Fork Yellow River IA 01-YEL-2005
from confluence with unnamed tributary in S3 T96N R7W Winneshiek Co. to headwaters in SE1/4 S34 T97 R8W Winneshiek Co.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 8/2/2016 11:01:51 AM
- Updated
- 1/30/2017 3:36:25 PM
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. This is a new IR Category 5 impairment due to an assessment error in the previous (2014) IR listing cycle. The presumptive Class B(WW1) aquatic life uses remain assessed (monitored) as “fully supported” (IR 2a) based on results of chemical/physical water quality monitoring in 2011. The source of data for this assessment is the results of water quality monitoring from April to October 2011 at Site 10 at Centennial Road (STORET station 15960039 and results of bacterial monitoring at this station from April to September 2014. Monitoring at station 15960039 during 2014 did not include analysis for parameters other than indicator bacteria.
Note: A TMDL for the bacterial impairments in 13 stream segments in the Yellow River basin was prepared by Iowa DNR in 2012 and approved by U.S. EPA in 2013. Due to completion of the TMDL, the bacteria impairments of the Class A1 recreational uses of those 13 segments are appropriate for Category 4a (impaired; TMDL approved) of Iowa's Integrated Report. This assessment segment (IA 01-YEL-0061_0, aka segment 2005), however, was not included in or covered by this TMDL. For the 2014 IR cycle, the bacteria impairment for this segment (IA 01-YEL-0161_0/2005) was mistakenly identified as an IR 4a impairment. To correct this error, this impairment is moved to IR Category 5p for the current (2016) IR cycle.
EXPLANATION: 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 mean of E. coli in the 20 samples collected during the recreation season of 2014 at station 15960039 was 1,684 orgs/100 ml, thus far exceeding the Class A1 criterion of 126 orgs/100 ml. Eighteen of the 20 samples (90%) exceeded Iowa’s 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 remain assessed (monitored) as “fully supported”. None of the 14 samples analyzed in 2011 for dissolved oxygen or the eight samples analyzed for ammonia violated the respective Class B(WW1) criteria. Three of the 14 samples collected in 2011 at station 15960039 violated the Class B(WW2) criterion for pH. The samples collected on June 2, August 2, and August 9, 2011, contained a pH levels of 9.2, 9.2, and 9.7 units, respectively, thus exceeding the Class B(WW1) criterion of 9.0 units. According to U.S. EPA guidelines (U.S. EPA 1997b, page 3-17), a violation frequency of greater than 10% for conventional parameters such as pH and dissolved oxygen suggests impairment of aquatic life uses. Based on IDNR’s assessment methodology, however, these results suggest that the frequency of violations is not significantly greater than10 percent; thus, these results do not suggest impairment of the presumptive Class B(WW1) aquatic life uses. Thus, these aquatic life uses remain assessed as “fully supported”.