Assessment Summary
The Class A1 use was assessed as "fully supported" based on the results of routine monitoring for indicator bacteria (E. coli). The Class BWW1 use remains assessed as "not supported" due to repeated fish kills immediately downriver from the Red Rock Dam. Results of water quality monitoring in this segment continue to suggest excellent water quality. The Class HH use was assessed as "fully supported" based on water quality monitoring data and for fish tissue sampling data.
Assessment Explanation
Sources of
Data:
|
Data Source
|
Data Source ID
|
Data Type
|
Data Age
|
Site ID
|
BioNet Site ID
|
Site Name
|
Site Description
|
|
USACE
|
12
|
WQ
|
CY 2016-2018
|
17630001
|
|
Des Moines River at Howell Station Landing
|
|
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
|
|
17630001
|
12
|
34 / 3
|
7.08
|
3.65
|
10.77
|
No
|
0
|
0%
|
No
|
Monitored
|
Full
|
Class A1 - pH:
|
Site ID
|
Data Source ID
|
# Samples / # Years
|
Maximum Value
|
Mean Value
|
Median Value
|
# Violations
|
% Violations
|
Significantly >10% Violations
|
Assessment Type
|
Support Level
|
|
17630001
|
12
|
65 / 3
|
8.98
|
8.21
|
8.19
|
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
|
|
17630001
|
12
|
Ammonia
|
65 / 3
|
1.02
|
0.1
|
0.04
|
0 / 1
|
0% / 2%
|
No
|
Monitored
|
Full
|
|
17630001
|
12
|
Chloride
|
3 / 3
|
30
|
26
|
25
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
17630001
|
12
|
Dissolved oxygen
|
65 / 3
|
19.6
|
10.9
|
10.2
|
NA / 0
|
NA / 0%
|
No
|
Monitored
|
Full
|
|
17630001
|
12
|
pH
|
65 / 3
|
8.98
|
8.21
|
8.19
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
17630001
|
12
|
Sulfate
|
4 / 3
|
50
|
36
|
37
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
17630001
|
12
|
Temperature
|
65 / 3
|
29.5
|
16.9
|
19.3
|
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
|
|
17630001
|
12
|
Cadmium
|
3 / 1
|
1.5
|
0.6
|
0.15
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
17630001
|
12
|
Copper
|
7 / 2
|
1.8
|
1
|
1.1
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
17630001
|
12
|
Lead
|
3 / 1
|
0.5
|
0.5
|
0.5
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
|
17630001
|
12
|
Mercury
|
3 / 1
|
0.025
|
0.0175
|
0.025
|
0 / 0
|
0% / 0%
|
No
|
Evaluated
|
Full
|
Class BWW1 - Fish kill Assessment:
The Des Moines River immediately downriver from Red Rock Dam has a history of fish kills caused by gas bubble trauma. For the period 1983 though 2013, 33 kills in the Red Rock Dam tailwater area have been attributed to gas bubble trauma (Lutz 2014). Fish kills caused by gas bubble trauma occur due to a large imbalance between the concentrations of atmospheric gasses in the water and the levels of these gasses dissolved in the blood of the fish. The concentrations of dissolved gasses such as oxygen and nitrogen in river water tend to equal the concentrations in the blood of a fish. When the levels of atmospheric gasses dissolved in river water become very high (i.e., super-saturated)—such as can happen when water moves through or over a large dam—the levels of these gasses will also rise in the blood of fish. As long as fish can stay in deeper water, the hydrostatic (water) pressure will keep these gasses fully dissolved in the fish’s blood. If, however, the flow of water downstream from the dam is decreased suddenly, the depth of the water will also decrease. With shallower water, fish are not able to move to deeper areas to keep the hydrostatic pressure sufficiently high to keep the gasses fully dissolved in their blood. During these conditions, the gasses dissolved in the fish’s blood will gradually come out of solution as bubbles, and these bubbles will interfere with blood circulation. Symptoms of gas bubble trauma in fish include gas blisters on the skin at the margins of the scales and as pop-eye (exophthalmia) where the eyes of the fish distend from the eye sockets. In the extreme case, blood circulation is disrupted to the point that fish kills occur.
One fish kill due to gas bubble trauma was reported during the 2012-14 assessment period; the most recent kill occurred on August 8, 2013. According to the DNR assessment/listing methodology, two consecutive IR cycles (five years) showing full support are needed before an existing impairment can be proposed for de-listing. Thus, due to reoccurring fish kills caused by gas bubble trauma, and due to the history of this type of fish kill in this river reach, the Class BWW1 aquatic life use remains assessed as "not supported” and will remain in IR Category 4c (i.e., impairment due to a non-pollutant stressor; TMDL not required).
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
|
|
17630001
|
12
|
Cadmium
|
3 / 1
|
1.5
|
0.6
|
0.15
|
3
|
No
|
Evaluated
|
Full
|
|
17630001
|
12
|
Copper
|
7 / 2
|
1.8
|
1
|
1.1
|
3
|
No
|
Evaluated
|
Full
|
|
17630001
|
12
|
Mercury
|
3 / 1
|
0.025
|
0.0175
|
0.025
|
3
|
No
|
Evaluated
|
Full
|
Class HH - Fish Tissue Sampling: Fish contaminant monitoring conducted downstream from Red Rock Reservoir by ISU/ACOE in 2012, 2013, and 2014.
Fish contaminant monitoring showed low levels of contaminants (dieldrin, heptachlor epoxide, chlordane, alachlor, and trifuluralin) in composite samples of whole fish common carp. Levels of PCBs in composite whole-fish carp samples for all Aroclors analyzed in from 2012 to 2014 (1016, 1221, 1232, 1242, 1248, 1254, and 1260) were all below levels of detection. Detection levels for PCB were high in all three years; thus, data for PCBs are inconclusive. The history of low levels of PCBs in fish from this river segment, however, suggest that PCB levels are below the one meal per week advisory trigger of 0.20 ppm for total PCBs (sum of Aroclors 1248, 1254, and 1260).
Composite samples of fillets from a predator species were analyzed for mercury in all three years. In 2012, the composite sample of largemouth bass fillets had low levels of mercury (0.14 mg/kg). The average levels of mercury in the composite sample of smallmouth bass fillets in 2013 was 0.10 ppm. Results were not reported for levels of mercury in the 2014 composite sample of predator fish. Levels of mercury in the samples from this river segment from 2012 and 2013 were below the one meal per week advisory threshold for mercury (0.30 ppm). Based on this information, fish consumption uses are assessed (monitored) as "fully supported".
The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. The fish contaminant data generated from the 2014, 2015, and 2016 ISU/ACOE samplings (or from previous ISU/ACOE monitoring) conducted in the segment of the Des Moines River immediately downstream from Red Rock Reservoir show that levels of contaminants (PCBs, chlordane and mercury) do not exceed any of the IDPH/DNR advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
