Assessment Summary
The Class BWW2 use was assessed as "not supported" based on biological sampling data. All other designated uses were "not assessed."
Note: A TMDL for organic enrichment in Mud Creek was prepared by DNR and approved by EPA in 2003; thus, this waterbody was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because all Section 303(d) impairments identified (organic enrichment, nutrient, and siltation) are potentially addressed by the TMDL, this waterbody remains in IR Category 4a.
Assessment Explanation
Data
Sources:
|
Data Source
|
Data Source ID
|
Data Type
|
Data Age
|
Site ID
|
Site Name
|
Site Description
|
|
Iowa DNR
|
6
|
BIO
|
See Below
|
386
|
Mud Creek
|
Wilton – Site 1
|
|
Iowa DNR
|
6
|
BIO
|
See Below
|
385
|
Mud Creek
|
Wilton – Site 3
|
|
Iowa DNR
|
6
|
BIO
|
See Below
|
384
|
Mud Creek
|
Wilton – Site 4
|
Presumptive Class A1 - No Data
Class
BWW2 - Biological Sampling:
Benthic
Macroinvertebrates:
|
BioNet Site ID
|
Date
|
Drainage Area
(mi2)
|
Ecoregion
|
Major Drainage
|
BM Sample Gear
|
BMIBI score
|
BMIBI Class
|
47f BMIBI BIT
|
BMIBI Pass/ Fail
|
|
384
|
9/15/03
|
74
|
47f
|
MS/WW
|
ArtSub
|
42
|
Fair
|
51
|
Fail
|
|
385
|
9/15/03
|
97
|
47f
|
MS/WW
|
ArtSub
|
39
|
Fair
|
51
|
Fail
|
|
386
|
9/15/03
|
105
|
47f
|
MS/WW
|
ArtSub
|
50
|
Fair
|
51
|
Fail
|
Fish:
|
BioNet Site ID
|
Date
|
Drainage Area
(mi2)
|
Ecoregion
|
Major Drainage
|
Riffle Stream?
|
FIBI score
|
FIBI Class
|
47f FIBI BIT
|
FIBI Pass/ Fail
|
|
385
|
9/17/03
|
97
|
47f
|
MS/WW
|
NA
|
27
|
Fair
|
36
|
Fail
|
|
384
|
9/16/03
|
74
|
47f
|
MS/WW
|
NA
|
25
|
Poor
|
36
|
Fail
|
|
386
|
9/16/03
|
105
|
47f
|
MS/WW
|
NA
|
40
|
Fair
|
36
|
Pass
|
Overall:
|
Community
|
Assessment Type
|
Assessment Result
|
Support Level
|
IR Category
|
Reason
|
|
Benthic
Macroinvertebrates
|
Evaluated
|
Fail (0/3)
|
Not
|
|
|
|
Fish
|
Evaluated
|
Fail (1/3)
|
Not
|
|
|
|
Overall
|
Evaluated
|
Fail
|
Not
|
4at
|
Assessment was
evaluated because it was based on samples not collected in the last five
years.
|
Class BWW2 - Historical Assessment:
Results of monitoring conducted in 2001 in support of TMDL development showed
only one violation of Class BWW2 water quality criteria for conventional
parameters and ammonia-nitrogen in the nine monthly samples collected between
March and November 2001: the level of dissolved oxygen in the sample collected
at Site 3 downstream from Durant on August 16, 2001 (4.7 mg/l) violated the
water quality criterion of 5.0 mg/l. Although no violations of Class BWW2
criteria for ammonia-nitrogen occurred, the maximum levels were moderately high
for Iowa streams (downstream to upstream): 0.48 mg/l at Site 1 SE of Wilton,
0.70 mg/l at Site 2 upstream from Wilton, 0.49 mg/l at Site 3 downstream from
Durant, 0.42 mg/l at Site 4 at the SE edge of Durant, and 0.19 mg/l at Site 5
upstream from Durant. Four of the six maximum ammonia values occurred on August
16.
Additional TMDL-related monitoring was conducted from June to September 2003 at
four stations on Mud Creek: three stations are near Wilton (DNR stations
11700006, 11700007, and 11700008); one station is located west of Durant
(11700005). Five samples were collected at each station during the
June-September period and the samples were analyzed for ammonia, dissolved
oxygen, pH, and temperature. No violations of Class BWW2 criteria for ammonia,
pH, or temperature occurred in the combined 20 samples. At station TMDL S2
(11700007), however, three of the five samples violated the Class BWW2
criterion for dissolved oxygen (5.0 mg/l). Although violations were relatively
minor (the minimum value was 4.5 mg/l), these results suggest the potential for
an ongoing water quality impairment in this segment of Mud Creek.
Despite the indications of relatively good water quality from TMDL-related
monitoring in 2001 and 2003, biological monitoring is better able to reflect
cumulative impacts of water quality over time and thus is believed to more
accurately represent water quality conditions of this segment of Mud Creek than
do results from the 2001 or 2003 TMDL monitoring sites. Thus, the assessment of
support of the designated aquatic life uses for this segment (not supported)
remains based on results of biological monitoring.
