Unnamed Tributary to Yellow River IA 01-YEL-2059
mouth (S14 T96N R7W Winneshiek Co.) to headwaters in NW1/4 S26 T96N. R7W Winneshiek Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 5/3/2019 11:20:02 AM
- Updated
- 7/11/2019 8:06:34 AM
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supporting” based on violations of water quality criteria for indicator bacteria (E. coli). The presumptive Class A1 uses are also assessed as "partially supporting" due to violations of water quality criteria for pH. The presumptive Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supporting” due to violations of the Class B(WW1) criteria for pH. Results of DNR/SHL biological sampling in 2007, however, suggested “full support” of the aquatic life uses. The sources of data for this assessment include (1) results of 2007 DNR/SHL biological sampling data and (2) results of water quality monitoring from April to October 2011 at 135th Street (Site 5; STORET station 15960037) and results of bacteria monitoring at this station from April to October 2014.
The presumptive Class A1 (primary contact recreation) uses are assessed (monitored) as "partially 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 15960037 was 903 orgs/100 ml. Seventeen of the 20 samples (85%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’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 3-35 of U.S. EPA 1997b). Note: The 2012 TMDL for bacteria impairments for streams in the Yellow River basin does not apply to the bacteria impairment in this assessment segment.
The Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supported” due to violations of Class B(WW1) criteria for pH at station 15960037. Four of the 14 samples (29%) collected from April to October 2011 exceeded the high pH criterion of 9.0 pH units with violation ranging from 9.2 to 9.7 pH 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 or dissolved oxygen suggests impairment of aquatic life uses. Based on DNR’s assessment methodology, these results suggest that the frequency of violations for pH is significantly greater than 10 percent; thus, these results suggest impairment of the Class B(WW1) aquatic life (and Class A1) uses. None of the other parameters monitored (dissolved oxygen, ammonia, or temperature) violated their respective Class B(WW1) criteria for the 14 samples collected during the April-October period of 2011.
In contrast, results of DNR/SHL biological sampling suggested that the aquatic life uses should be assessed (evaluated) as “fully supporting” based on data collected in 2007 as part of the DNR/SHL stream biological sampling program. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2007 FIBI score was 78 (excellent). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 52. Even though this site passed the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.