Assessment Summary
The presumptive 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 "partially supported" due to violations of state water quality criteria for dissolved oxygen. The Class HH use was assessed as “full supported” based on Class HH-F toxics monitoring.
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 5p (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
|
|
USGS
|
11
|
WQ
|
CY 2016-2018
|
5451210
|
South Fork Iowa River NE of New
Providence, IA
|
|
|
NLAE
|
20
|
WQ
|
CY 2014-2015
|
SF450
|
South Fork Iowa River NE of New
Providence, IA
|
|
Presumptive
Class A1 - Indicator Bacteria: Historical
|
Site ID
|
Data Source ID
|
# Samples / # Years
|
2014 Geometric mean
|
2015 Geometric mean
|
Annual Geomean Violation
|
# Violations
|
% Violations
|
Significantly >10% Violations
|
Assessment Type
|
Support Level
|
|
SF450
|
20
|
16 / 2
|
194
|
695
|
Yes
|
10
|
63%
|
Yes
|
Evaluated
|
Partial
|
Presumptive
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
|
|
5451210
|
11
|
73 / 3
|
8.5
|
8
|
8.1
|
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
|
|
5451210
|
11
|
Ammonia
|
72 / 3
|
1.15
|
0.06
|
0.02
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
Chloride
|
71 / 3
|
37.8
|
24
|
23.9
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
Dissolved oxygen
|
71 / 3
|
14.6
|
10.6
|
10.3
|
NA / 0
|
NA / 0%
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
pH
|
73 / 3
|
8.5
|
8
|
8.1
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
Sulfate
|
71 / 3
|
38.4
|
23.3
|
24
|
0 / NA
|
0% / NA
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
Temperature
|
73 / 3
|
26
|
13.5
|
16.7
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
Class
BWW1 - Continuous Monitoring: Historical monitoring conducted by the National
Laboratory for Agriculture and the Environment from 2010-2014 near New
Providence (station SF450).
The
assessment of support of the Class BWW1 aquatic life uses is also based on
monitoring at NLAE station SF450 near New Providence. Continuous monitoring
data for dissolved oxygen, pH, and water temperature for the years 2010 through
2014 were available for this station. Eighteen of the 462 daily maximum values
(3.9%) for pH exceeded the Class BWW1 high pH criterion of 9.0; the maximum pH
reported for this period was 9.2 units. Ten of the 462 daily minimum pH values
(2.2%) violated the low pH criterion of 6.5 pH units (the lowest minimum daily
value was 6.2 units). Seventeen of the 511 daily maximum values for water
temperature (3.3%) exceeded Iowa’s added heat criterion of 32C (maximum value =
35.4C). The monitoring results for pH and water temperature at station SF450 do
not suggest impairment.
Of
the 486 daily minimum values for dissolved oxygen generated at monitoring site
SF450 over the 2010-2014 monitoring period, 64 values (31.2%) were below the
5.0 mg/l Class BWW1 criterion (not < 5.0 mg/l at any time during a 24-hour
period). According to U.S. EPA guidelines and Iowa DNR’s assessment
methodology, the percentage of samples that violated the 5.0 mg/l standard was significantly
greater than 10%. Thus, the Class BWW1 aquatic life uses are assessed as
“impaired” (partially supporting). This impairment is due primarily due
violations of dissolved oxygen criteria during the warm dry summer of 2012.
During the period from July 1 to September 15, 2012, the daily minimum values
for dissolved oxygen in 52 of the 77 samples collected (68%) were less than the
5.0 mg/l dissolved oxygen standard. Over 80% of the total number of violations
of the dissolved oxygen criterion at this station (52 of 64) during the five-year
period from 2010-2014 occurred during this 78-day period during summer
2012.Thus, based on the results of water quality monitoring, the Class BWW1
uses are assessed as “partially supported”.
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
|
|
5451210
|
11
|
Arsenic
|
72 / 3
|
31.6
|
2.2
|
1.6
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
|
5451210
|
11
|
Selenium
|
72 / 3
|
3.6
|
1.84
|
2
|
0 / 0
|
0% / 0%
|
No
|
Monitored
|
Full
|
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
|
|
5451210
|
11
|
Selenium
|
72 / 3
|
3.6
|
1.84
|
2
|
0
|
No
|
Monitored
|
Full
|
Class
HH - Fish Tissue Sampling: No Data
