Iowa River IA 02-IOW-646
from confluence with South Fork Iowa R. (S25 T87N R20W Hardin Co.) to confluence with Pine Cr. in S8 T87N R19W Hardin Co.
- Assessment Cycle
- 2024
- Release Status
- Pending
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 11/1/2023 8:12:56 AM
- Updated
- 12/15/2023 8:53:22 AM
Assessment Summary
The Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class HH (fish consumption) use was assessed as “not supported” due to a historic one meal/week mercury consumption advisory for any predator fish in this segment. 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 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).
Assessment Explanation
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2020-2022 10420001 Iowa
River near Gifford
Iowa DNR 6 BIO See Below 839 Iowa
River Gifford Site ID Data Source ID # Samples per Year (2020/ 2021/2022) 2020 Geometric Mean 2021 Geometric Mean 2022 Geometric Mean Violates Annual Geometric Mean? # 2020 SSM violations / SSM Violations needed for impairment # 2021 SSM violations / SSM Violations needed for impairment # 2022 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 10420001 6 8/8/9 83 154 223 YES 2 / 3 3 / 3 4 / 3 YES Mon Not Site ID Data Source ID # Samples / # Years Minimum Value Maximum Value Mean Value # Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 10420001 6 36 / 3 7.2 8.9 8.2 0 7 NO Mon Full Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Mean Value # Violations # Acute / Chronic Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 10420001 6 Chloride 36 / 3 14 40 25 NA 0 / 0 7 NO Mon Full 10420001 6 Dissolved Oxygen 36 / 3 7.1 14.3 11.1 0 NA / NA 7 NO Mon Full 10420001 6 pH 36 / 3 7.2 8.9 8.2 0 NA / NA 7 NO Mon Full 10420001 6 Sulfate 36 / 3 19 60 36 0 NA / NA 7 NO Mon Full 10420001 6 Temperature 36 / 3 0 27.1 11.7 0 NA / NA 7 NO Mon Full Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations >1 Acute / Chronic Violation Assessment Type Support Level 10420001 6 Ammonia 36 / 3 0.23 0.04 0.02 0 / 0 NO Mon Full 10420001 6 Cadmium 20 / 3 0.5 0.5 0.5 0 / 0 NO Mon Full 10420001 6 Chromium 20 / 3 1.2 0.7 0.7 0 / 0 NO Mon Full 10420001 6 Lead 20 / 3 1 0.91 1 0 / 0 NO Mon Full 10420001 6 Nickel 20 / 3 3.2 1.6 1.4 0 / 0 NO Mon Full 10420001 6 Selenium 18 / 2 3 1.3 1.5 0 / 0 NO Mon Full 10420001 6 Silver 20 / 3 1 0.902 1 0 / 0 NO Mon Full 10420001 6 Zinc 20 / 3 4 0.9 0.5 0 / 0 NO Mon Full Site ID Date Drainage Area (mi2) Ecoregion Major Drainage BM Sample Gear BMIBI score BMIBI Class 47f BMIBI BIT BMIBI Pass/Fail 839 8/25/22 774.7 47f MS Floating Art Sub 41 Fair 51 Fail 839 8/2/19 774.7 47f MS Floating Art Sub 66 Good 51 Pass Community Assessment Type Assessment Result Support Level IR Category Reason Benthic
Macroinvertebrates Evaluated Fail (1/2) WINOFI Assessment was evaluated because the
drainage area Overall Evaluated Fail WINOFI 3bu of the sample site was greater than the
calibrated range. Support Level Not A historic one
meal/week mercury consumption advisory for any predator fish exists on this
segment. Based on IR Methodology, the Class HH (fish consumption) use was
assessed as “not supported.” Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value Number of Non - Detects Mean Value > Criterion or MCL Assessment Type Support Level 10420001 6 Selenium 18 / 2 3 1.3 1.5 8 NO Mon Full
Class A1 - Indicator Bacteria:
Class A1 - pH:
Class BWW1 - Binomial Parameters:
Class BWW1 - Toxic Parameters:
Class BWW1 - Biological Sampling:
Benthic Macroinvertebrates:
Overall:
Class HH - Fish Tissue Sampling:
Class HH-F - Toxic Parameters:
Assessment Key Dates
1/13/2020 | Monitoring Start |
12/6/2022 | Monitoring End |
8/2/2019 | Biological Monitoring |
3/9/2018 | TMDL Completed |
8/5/2022 | Biological Monitoring |
Methods
200 | Physical/Chemical Monitoring |
260 | Fish tissue analysis |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
420 | Indicator bacteria monitoring |