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
- 2020
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 9/3/2020 9:36:51 AM
- Updated
- 10/14/2020 1:00:30 PM
Assessment Summary
The Class A1 use was assessed as "partially supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW1 use was assessed as "fully supported" based on water quality monitoring data and biological sampling data. The Class HH use remains assessed as “partially supported” based on fish tissue sampling data and due to the existence of a one meal per week fish consumption advisory for mercury. 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
Sources
of Data: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2016-2018 10420001 Iowa River near Gifford Iowa DNR 6 BIO See Below 839 Iowa River Gifford Iowa DNR 6 FT See Below 3 Iowa River at Marshalltown Site is located in Segment 641 Class
A1 - Indicator Bacteria: Site ID Data Source ID # Samples / # Years 2016 Geometric Mean 2017 Geometric Mean 2018 Geometric Mean Annual Geometric Mean Violation # Violations % Violations Significantly >10% Violations Assessment Type Support Level 10420001 6 21 / 3 223.3 139.63 275.6 Yes 9 43% Yes Monitored Partial Class
A - pH: Site ID Data Source ID # Samples / # Years Maximum Value Mean Value Median Value # Violations % Violations Significantly >10% Violations Assessment Type Support Level 10420001 6 35 / 3 8.9 8.2 8.3 0 0% No Monitored Full Class
BWW1 - 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 10420001 6 Ammonia 35 / 3 1.2 0.08 0.02 0 / 0 0% / 0% No Monitored Full 10420001 6 Chloride 36 / 3 28 19.1 19 0 / 0 0% / 0% No Monitored Full 10420001 6 Dissolved oxygen 36 / 3 14.5 10.9 10.7 NA / 0 NA / 0% No Monitored Full 10420001 6 pH 35 / 3 8.9 8.2 8.3 0 / NA 0% / NA No Monitored Full 10420001 6 Sulfate 36 / 3 55 29 27 0 / NA 0% / NA No Monitored Full 10420001 6 Temperature 36 / 3 26.3 11.4 11.7 0 / 0 0% / 0% No Monitored Full Class
BWW1 - Toxic Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations % Acute/ Chronic Violations >1 Acute / Chronic Violation Assessment Type Support Level 10420001 6 Aluminum 9 / 2 1.7 0.727 0.82 0 / 0 0% / 0% No Evaluated Full 10420001 6 Arsenic 9 / 2 2.6 2 1.9 0 / 0 0% / 0% No Evaluated Full 10420001 6 Cadmium 9 / 2 0.025 0.025 0.025 0 / 0 0% / 0% No Evaluated Full 10420001 6 Chromium 9 / 2 1.4 0.9 1.1 0 / 0 0% / 0% No Evaluated Full 10420001 6 Copper 9 / 2 4.2 1.27 0.89 0 / 0 0% / 0% No Evaluated Full 10420001 6 Lead 9 / 2 0.1 0.058 0.06 0 / 0 0% / 0% No Evaluated Full 10420001 6 Nickel 9 / 2 3.7 2.9 2.8 0 / 0 0% / 0% No Evaluated Full 10420001 6 Selenium 9 / 2 2.2 1.39 1.4 0 / 0 0% / 0% No Evaluated Full 10420001 6 Zinc 9 / 2 2.7 1.33 1.1 0 / 0 0% / 0% No Evaluated Full Class
BWW1 - Biological Sampling: Benthic
Macroinvertebrates: BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/ Thermal BM Sample Gear BMIBI score BMIBI Class 47f BMIBI BIT BMIBI Pass/ Fail 839 8/28/14 775 47f MS/WW ArtSub 51 Fair 51 Pass 839 9/11/13 775 47f MS/WW ArtSub 52 Fair 51 Pass Overall
Assessment: Community Assessment Type Assessment Result Support Level Earned IR Category Actual IR Category Reason Benthic Macroinvertebrates Evaluated Pass (2/2) Full 1 1 Assessment
is evaluated because the drainage area of the site is larger than calibrated
range. Class
HH-F - Toxic Parameters: 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 Cadmium 9 / 2 0.025 0.025 0.025 9 No All Non-Detect Full 10420001 6 Chromium 9 / 2 1.4 0.9 1.1 0 No Evaluated Full 10420001 6 Copper 9 / 2 4.2 1.27 0.89 0 No Evaluated Full 10420001 6 Nickel 9 / 2 3.7 2.9 2.8 0 No Evaluated Full 10420001 6 Selenium 9 / 2 2.2 1.39 1.4 0 No Evaluated Full 10420001 6 Zinc 9 / 2 2.7 1.33 1.1 0 No Evaluated Full Class
HH – Fish Tissue Sampling: Site ID Date Species Name Biopart # in sample chlordane result chlordane violation (>0.6)? PCBs result PCBs violation (>0.2)? Hg result Hg violation (>0.3)? Assessment Type Support Level 3 9/14/2011 common carp fillet 5 <0.03 No <0.09 No 0.146 No Evaluated Full 3 9/14/2011 walleye plug 4 0.323 Yes Evaluated Partial 3 9/26/2012 walleye plug 3 0.308 Yes Evaluated Partial A one meal/week consumption advisory for mercury exists on this segment of the Iowa River – seeIowa Consumption Advisories According to the
Iowa DNR assessment/listing methodology, the existence of a one meal per week
consumption advisory indicates that the fish consumption uses should be
assessed as “partially supported.”
Assessment Key Dates
9/14/2011 | Fish Tissue Monitoring |
9/26/2012 | Fish Tissue Monitoring |
1/7/2016 | Fixed Monitoring Start Date |
12/5/2018 | Fixed Monitoring End Date |
9/11/2013 | Biological Monitoring |
8/28/2014 | Biological Monitoring |
3/9/2018 | TMDL Completed |
Methods
150 | Monitoring data more than 5 years old |
230 | Fixed station physical/chemical (conventional plus toxic pollutants) |
260 | Fish tissue analysis |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
420 | Indicator bacteria monitoring |