Milford Creek IA 06-LSR-1666
mouth (S14 T98N R37W Dickinson Co.) to confluence with unnamed tributary in S18 T98N R36W Dickinson Co.
- Cycle
- 2020
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 9/22/2020 12:47:54 PM
- Updated
- 10/16/2020 3:16:33 PM
The Class BWW2 aquatic life use remains assessed as "partially supported" based on 2001 and 2005 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).
Sources of Data: 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) Class
BWW2 - Biological Sampling: Benthic
Macroinvertebrates: BioNet Site ID Date Drainage Area (mi2) Ecoregion Major Drainage/ Thermal BM Sample Gear BMIBI score BMIBI Class 47b BMIBI BIT BMIBI Pass/ Fail 244 9/14/05 136 47b MO/WW Hess 13 Poor 62 Fail 244 9/5/01 136 47b MO/WW Hess 43 Fair 62 Fail Overall: Community Assessment Type Assessment Result Support Level Earned IR Category Actual IR Category Reason Benthic
Macroinvertebrates Evaluated Fail (0/2) Partial 3bc 4a Assessment
is evaluated because it was based on samples not collected in the last five
years. Class BWW2 - Conventional Parameters: 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 B(WW2) 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. 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. 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.