South Fork Iowa River IA 02-IOW-749
from confluence with unnamed tributary in W 1/2 S19 T88N R21W Hardin Co. to confluence with unnamed tributary in E 1/2 S11 T88N R22W Hardin Co.
- Cycle
- 2020
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 10/8/2020 11:56:05 AM
- Updated
- 10/12/2020 9:02:18 AM
The presumptive Class A1 use remains assessed as "partially supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW2 use remains assessed as “fully supported” based on limited water quality monitoring data. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5p (impaired; TMDL needed) to 4a (impaired; TMDL approved).
Sources
of Data: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description NLAE 20 WQ CY 2010-2012 SF400 South Fork Iowa River 2 miles NNE of Buckeye USGS 11 WQ CY 2013 05451112 South Fork Iowa River Near Buckeye Presumptive Class A1 - Indicator Bacteria: Site ID Data Source ID # Samples / # Years 2010 Geometric Mean 2011 Geometric Mean 2012 Geometric Mean Annual Geometric Mean
Violation # Violations % Violations Significantly >10%
Violations Assessment Type Support Level SF400 20 23 / 3 304 361 344 Yes 15 65% Yes Evaluated Partial Presumptive Class A1 - pH: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic
Violations % Acute/ Chronic
Violations Significantly >10%
Violations Assessment Type Support Level 05451112 11 pH 13 / 1 8.3 8 8 0 / NA 0% / NA No Evaluated Full Class BWW2 – Conventional
Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic
Violations % Acute/ Chronic
Violations Significantly >10%
Violations Assessment Type Support Level 05451112 11 Ammonia 13 / 1 0.11 0.03 0.03 0 / 0 0% / 0% No Evaluated Full 05451112 11 Chloride 10 / 1 36 30 30 NA / 0 NA / 0% No Evaluated Full 05451112 11 Dissolved oxygen 13 / 1 11.7 8.9 8.8 NA / 0 NA / 0% No Evaluated Full 05451112 11 pH 13 / 1 8.3 8 8 0 / NA 0% / NA No Evaluated Full 05451112 11 Sulfate 10 / 1 38 29 29 NA / 0 NA / 0% No Evaluated Full 05451112 11 Temperature 15 / 1 28.1 19.4 18.9 0 / 0 0% / 0% No Evaluated Full Class BWW2 – Continuous
Monitoring Data: Monitoring at station
SF400 from 2010-2012 included continuous monitoring for dissolved oxygen, pH,
and water temperature. None of the 530 daily maximum and minimum values for pH
exceeded the respective Class BWW2 pH criteria of 9.0 and 6.5 pH units. The
respective maximum and minimum pH values reported for this period were 9.0 and
7 pH units. Eight of the 529 daily maximum values for water temperature (1.5%)
exceeded Iowa’s added heat criterion of 32C (maximum value = 33.8C). Of the 468
daily minimum values for dissolved oxygen generated at monitoring site SF400
over the 2010-2012 monitoring period, only 1 value (0.2%) was below the 5.0
mg/l Class BWW2 criterion (not < 5.0 mg/l during 16 hours of a 24-hour
period), and no values were below Iowa’s Class BWW2 criterion for a minimum
dissolved oxygen of 4.0 mg/l at any time during a 24-hour period (minimum value
= 4.95 mg/l). The monitoring results for pH, dissolved oxygen and water
temperature at station SF400 do not suggest impairment of the Class BWW2
aquatic life use.