Milford Creek IA 06-LSR-1666
mouth (S14 T98N R37W Dickinson Co.) to confluence with unnamed tributary in S18 T98N R36W Dickinson Co.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 12/30/2021 2:43:54 PM
- Updated
- 1/31/2022 12:57:02 PM
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 phosphorus was approved by EPA in December 2008. As noted in the TMDL, DNR’s 2004 stressor identification document for Milford Creek identified excessive aquatic vegetation (both algae and macrophytes) and low levels of dissolved oxygen as the primary stressors of the fish and aquatic macroinvertebrate communities of this stream segment. The high level of phosphorus in this stream, as documented as part of previous Section 305(b) assessments and as part of the 2008 TMDL, was identified as the causal factor behind the responses of excessive vegetation and low levels of dissolved oxygen. Because the 2008 TMDL covers these causal factors, the biological impairment identified for the 2004 and 2006 listing cycles was moved from IR Category 5b to Category 4a (impaired; TMDL approved).
Data
Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 BIO See Below 244 Milford Creek Milford – DS TMDL Iowa DNR 6 WQ See Below 11300002 Milford Creek Site 49 Iowa DNR 6 WQ See Below 11300015 Milford Creek At 225 Ave (Site 2) Benthic
Macroinvertebrates: BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage BM Sample Gear BMIBI score BMIBI Class 47b BMIBI BIT BMIBI Pass/Fail 244 9/14/05 136 47b MO Hess 13 Poor 62 Fail 244 9/5/01 136 47b MO Hess 43 Fair 62 Fail Community Assessment Type Assessment Result Support Level IR Category Reason Benthic Macroinvertebrates Evaluated Fail (0/2) Not 4a Assessment was evaluated because it was
based on samples not collected in the last five years. Results of chemical
monitoring conducted in this segment as part of TMDL-related monitoring during
the period from May 2004 to September 2005 suggest water quality problems in
this stream reach but do not suggest impairment of the Class BWW2 aquatic life
use. Two of 20 samples (10%) violated the Class BWW2 criterion for dissolved
oxygen of 5 mg/l; these samples were collected on August 4 (3.9 mg/l) and
August 10 (4.2 mg/l) of 2004. One of 17 samples (6%) violated the Class BWW2
criterion for pH. The pH of the sample collected on June 7, 2004 was 9.3 units,
thus exceeding the criterion of 9.0 pH units. Two of 14 samples collected from
2004-2005 violated the Class BWW2 chronic criteria for ammonia; these samples
were collected on July 6, 2004 (4.5 mg/l) and July 12, 2004 (0.74 mg/l). Based
on DNR’s assessment methodology, however, these results do not suggest that the
violation frequency for dissolved oxygen, pH or ammonia is significantly
greater than 10% and thus do not suggest impairment of the Class BWW2 use of
this segment of Milford Creek. This stream has
historically shown elevated levels of phosphorus. The mean, median, and maximum
total phosphorus levels for the 24 sampling events from May 2004 through
September 2005 at TMDL monitoring station 49 in lower Milford Creek were 1.4,
1.5, and 3.0 mg/l, respectively. Summary statistics for dissolved phosphorus,
measured as orthophosphate, for these 24 sampling events (mean, median, and
maximum) were 1.2, 1.3, and 3.1 mg/l, respectively.
Class BWW2 - Biological Sampling:
Overall:
Class BWW2 -
Conventional Parameters:
Limited monitoring at TMDL Site 2 (Station 11300015; 1 mile SSE of Milford)
from July to September 2005 did not show violations of Class BWW2 criteria; no
violations occurred for ammonia (maximum = 0.21 mg/l), pH (range of 7.9-8.4),
or dissolved oxygen (minimum = 6.8 mg/l) in the four samples collected during
this period. Although these results suggested good water quality, the number of
samples and period of time covered was limited and does not provide for
development of a higher confidence (monitored) assessment.