Assessment Summary
The Class A1 use was assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The Class BWW1 use remains assessed as “not supported” based on fish kills in and upstream from this segment. The Class HH use was assessed as "fully supported" based on water quality monitoring data.
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
|
10890001
|
Des
Moines River near Keosauqua
|
|
USGS
|
11
|
WQ
|
CY 2020-2022
|
5490500
|
Des
Moines River at Keosauqua, IA
|
|
Iowa DNR
|
6
|
BIO
|
See Below
|
946
|
Des
Moines River
|
Keosauqua
|
Iowa DNR
|
6
|
BIO
|
See Below
|
1258
|
Des
Moines River
|
Bonaparte
(REMAP #414)
|
Class A1 - Indicator Bacteria:
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
|
10890001
|
6
|
8/8/8
|
106
|
80
|
135
|
YES
|
1 / 3
|
3 / 3
|
3 / 3
|
YES
|
Mon
|
Not
|
Class A1 – pH:
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
|
10890001
|
6
|
36 / 3
|
8
|
9.2
|
8.5
|
2
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
78 / 3
|
7.7
|
9.4
|
8.4
|
2
|
12
|
NO
|
Mon
|
Full
|
Class BWW1 - Binomial Parameters:
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
|
10890001
|
6
|
Chloride
|
36 / 3
|
16
|
70
|
37
|
NA
|
0 / 0
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
Chloride
|
38 / 3
|
17.3
|
58.3
|
33.8
|
NA
|
0 / 0
|
7
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Dissolved Oxygen
|
36 / 3
|
6.9
|
17.5
|
11.6
|
0
|
NA / NA
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
Dissolved Oxygen
|
41 / 3
|
7.2
|
22.8
|
11.9
|
0
|
NA / NA
|
8
|
NO
|
Mon
|
Full
|
10890001
|
6
|
pH
|
36 / 3
|
8
|
9.2
|
8.5
|
2
|
NA / NA
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
pH
|
78 / 3
|
7.7
|
9.4
|
8.4
|
2
|
NA / NA
|
12
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Sulfate
|
36 / 3
|
30
|
110
|
67
|
0
|
NA / NA
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
Sulfate
|
38 / 3
|
0.48
|
118
|
61.89
|
0
|
NA / NA
|
7
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Temperature
|
36 / 3
|
0.1
|
30.3
|
13.7
|
0
|
NA / NA
|
7
|
NO
|
Mon
|
Full
|
5490500
|
11
|
Temperature
|
41 / 3
|
-0.1
|
30.1
|
17.3
|
0
|
NA / NA
|
8
|
NO
|
Mon
|
Full
|
Class BWW1 - Toxic Parameters:
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
|
10890001
|
6
|
Ammonia
|
36 / 3
|
0.22
|
0.03
|
0.02
|
0 / 0
|
NO
|
Mon
|
Full
|
5490500
|
11
|
Ammonia
|
39 / 3
|
0.29
|
0.03
|
0.01
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Cadmium
|
20 / 3
|
0.5
|
0.5
|
0.5
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Chromium
|
20 / 3
|
2
|
0.64
|
0.5
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Lead
|
20 / 3
|
1
|
0.9
|
1
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Nickel
|
20 / 3
|
3.6
|
2.4
|
2.4
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Selenium
|
18 / 2
|
2
|
1
|
0.8
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Silver
|
20 / 3
|
1
|
0.902
|
1
|
0 / 0
|
NO
|
Mon
|
Full
|
10890001
|
6
|
Zinc
|
20 / 3
|
3.2
|
1.3
|
0.8
|
0 / 0
|
NO
|
Mon
|
Full
|
Class BWW1 - Biological Sampling:
Benthic Macroinvertebrates:
Site ID
|
Date
|
Drainage Area (mi2)
|
Ecoregion
|
Major Drainage
|
BM Sample Gear
|
BMIBI score
|
BMIBI Class
|
40a BMIBI BIT
|
BMIBI Pass/Fail
|
946
|
7/27/20
|
14038
|
40a
|
MS
|
Floating Art Sub
|
60
|
Good
|
41
|
Pass
|
1258
|
7/27/20
|
14100
|
40a
|
MS
|
Hess
|
58
|
Good
|
41
|
Pass
|
Fish:
Site ID
|
Date
|
Drainage Area (mi2)
|
Ecoregion
|
Major Drainage
|
Riffle Stream?
|
FIBI score
|
FIBI Class
|
40a FIBI BIT
|
FIBI Pass/Fail
|
1258
|
7/28/20
|
14100
|
40a
|
MS
|
NA
|
30
|
Fair
|
33
|
Pass*
|
Overall:
Community
|
Assessment Type
|
Assessment Result
|
Support Level
|
IR Category
|
Reason
|
Benthic
Macroinvertebrates
|
Evaluated
|
Pass (2/2)
|
Full
|
|
*The FIBI score passed after the 7 point UAV
was applied to single sample.
|
Fish
|
Evaluated
|
Pass (1/1)
|
Full
|
|
The assessment was evaluated because the
drainage areas of the sites were
|
Overall
|
Evaluated
|
Pass
|
Full
|
1
|
greater than the calibrated range.
|
Class BWW1 – Fishkill Assessment:
The Class BWW1 aquatic
life use remains assessed as “not 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 20 years that appear to involve primarily shovelnose sturgeon
(Scaphirhynchus platorynchus). Although the cause fish 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, if a cause of a fish kill 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 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 are usually placed in IR subcategory 3b and are added to the
state’s list of waters in need of further investigation (WINOFI). Due however
to (1) the repeated occurrence of these kills over the last 20 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 remains on Iowa’s 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
|
Selenium
|
18 / 2
|
2
|
1
|
0.8
|
9
|
NO
|
Mon
|
Full
|