Assessment Summary
The Class A1 use was assessed as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The Class BWW1 use remains assessed as “partially supported” based on fish kills in, and upstream from, this assessment segment. The Class HH (fish consumption) use remains assessed as "fully supported" based water quality monitoring.
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
|
10890001
|
Des Moines River near Keosauqua
|
|
|
USGS
|
11
|
WQ
|
CY 2016-2018
|
5490500
|
Des Moines River at Keosauqua, IA
|
|
|
Iowa DNR
|
6
|
BIO
|
See Below
|
946
|
Des Moines River
|
Keosauqua
|
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
|
|
10890001
|
6
|
24 / 3
|
108.04
|
262.9
|
48.56
|
Yes
|
6
|
25%
|
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
|
|
10890001
|
6
|
36 / 3
|
9.3
|
8.4
|
8.5
|
1
|
3%
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
39 / 3
|
9.2
|
8.3
|
8.2
|
1
|
3%
|
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
|
|
10890001
|
6
|
Ammonia
|
36 / 3
|
0.62
|
0.05
|
0.02
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
Ammonia
|
37 / 3
|
0.45
|
0.04
|
0.01
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Chloride
|
36 / 3
|
54
|
27
|
26
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
Chloride
|
39 / 3
|
52.4
|
25
|
24.4
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Dissolved oxygen
|
36 / 3
|
19.8
|
11.2
|
10.8
|
NA / 0
|
NA / 0%
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
Dissolved oxygen
|
39 / 3
|
16.2
|
11
|
10.8
|
NA / 0
|
NA / 0%
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
pH
|
36 / 3
|
9.3
|
8.4
|
8.5
|
1 / NA
|
3% / NA
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
pH
|
39 / 3
|
9.2
|
8.3
|
8.2
|
1 / NA
|
3% / NA
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Sulfate
|
36 / 3
|
110
|
50
|
45
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
Sulfate
|
39 / 3
|
82.8
|
47.6
|
43.1
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Temperature
|
36 / 3
|
26.7
|
13.4
|
12.4
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5490500
|
11
|
Temperature
|
37 / 3
|
29
|
15.3
|
14.8
|
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
|
|
10890001
|
6
|
Aluminum
|
9 / 2
|
1.5
|
0.685
|
0.81
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Arsenic
|
9 / 2
|
5.1
|
3.1
|
2.9
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
5490500
|
11
|
Arsenic
|
39 / 3
|
4.2
|
2.2
|
2
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Cadmium
|
9 / 2
|
0.05
|
0.028
|
0.025
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Chromium
|
9 / 2
|
1.2
|
0.9
|
0.83
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Copper
|
9 / 2
|
2
|
1.5
|
1.6
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Lead
|
9 / 2
|
0.35
|
0.117
|
0.06
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Nickel
|
9 / 2
|
4.2
|
3.2
|
3
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Selenium
|
9 / 2
|
3.3
|
1.96
|
2
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
5490500
|
11
|
Selenium
|
39 / 3
|
2.7
|
1.7
|
1.8
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Zinc
|
9 / 2
|
3.9
|
1.77
|
1.6
|
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
|
40a BMIBI BIT
|
BMIBI Pass/ Fail
|
|
946
|
9/6/16
|
14038
|
40a
|
MS/WW
|
Float ArtSub
|
74
|
Good
|
41
|
Pass
|
Overall:
|
Community
|
Assessment Type
|
Assessment Result
|
Support Level
|
Earned IR Category
|
Actual IR Category
|
Reason
|
|
Benthic
Macroinvertebrates
|
Evaluated
|
Pass
|
Full
|
1
|
1
|
Assessment
is evaluated because it was based on a single sample and the drainage area of
the samples site was larger than the calibrated range.
|
Class
BWW1 – Fishkill Assessment:
The Class BWW1
aquatic life use remains assessed as “partially supported” due to fish kills on
July 10, 2006, and on July 7, 2012 on the reach of river between Eldon (Wapello
Co.) and Douds (Van Buren Co.). These kills are in a series of kills that have
occurred over the last 15 years or so that appear to involve primarily
shovelnose sturgeon (Scaphirhynchus platorynchus). Although the cause of the
three recent kills and the previous kills remains unknown, the leading
hypotheses are (1) that very high water temperatures, very low river flows, and
elevated pH levels combine to make ambient levels of ammonia in the river toxic
to the ammonia-intolerant shovelnose sturgeon and (2) that the kills are caused
by a virus specific to shovelnose sturgeon. The most recent kill in July 2012
was especially severe. According to the local DNR Fisheries biologist, the kill
was reported on the lower Des Moines River on July 7, 2012, from approximately
Eldon (downriver from Ottumwa) to Farmington in Van Buren County. An estimated
57,000 fish were killed including at least 35,000 shovelnose sturgeon. No
specific cause of the kill was identified, but low flow conditions, flow
alterations, and very high water temperatures (95+F) are believed to have
contributed to the kill.
According to
DNR's assessment methodology for Section 305(b) reporting, occurrence of a
single pollution-caused fish kill within the most recent three-year period
indicates that the aquatic life uses of a waterbody are only "partially
supported.” Thus, the Class BWW1 aquatic life uses of this river reach were
assessed as "partially supported” (303(d) impaired). Also, according to
DNR’s assessment methodology, if a cause of a fishkill was not identified
during the DNR investigation (cause = "unknown"), or if the kill was
attributed to non-pollutant causes (e.g., winterkill), the assessment type will
be considered “evaluated.” Such assessments, although suitable for Section
305(b) reporting, typically lack the degree of confidence to support addition
to the state Section 303(d) list of impaired waters (Category 5 of the
Integrated Report). Waterbodies affected by such fish kills at usually placed
in IR subcategories 2b or 3b and are added to the state’s list of “waters in
need of further investigation”. Due however to (1) the repeated occurrence of
these kills over the last 15 years in Wapello and Van Buren counties, (2) the large
numbers of sturgeon killed (thousands), (3) the likelihood that these kills are
caused by a pollutant and (4) the possibility that the kills have extended
further downstream (possibly to Bonaparte), this impairment was added to Iowa’s
2008 Section 303(d) list (Category 5 of the Integrated Report).
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
|
|
10890001
|
6
|
Cadmium
|
9 / 2
|
0.05
|
0.028
|
0.025
|
8
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Chromium
|
9 / 2
|
1.2
|
0.9
|
0.83
|
0
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Copper
|
9 / 2
|
2
|
1.5
|
1.6
|
0
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Nickel
|
9 / 2
|
4.2
|
3.2
|
3
|
0
|
No
|
Evaluated
|
Full
|
|
10890001
|
6
|
Selenium
|
9 / 2
|
3.3
|
1.96
|
2
|
0
|
No
|
Evaluated
|
Full
|
|
5490500
|
11
|
Selenium
|
39 / 3
|
2.7
|
1.7
|
1.8
|
0
|
No
|
Monitored
|
Full
|
|
10890001
|
6
|
Zinc
|
9 / 2
|
3.9
|
1.77
|
1.6
|
0
|
No
|
Evaluated
|
Full
|
