Soap Creek IA 04-LDM-1033
from confluence with Little Soap Cr. (S1 T70N R13W Davis Co.) to confluence with unnamed tributary in S31 T71N R16W Monroe Co.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 5/14/2019 2:27:10 PM
- Updated
- 5/14/2019 2:28:46 PM
The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (evaluated) as “partially supporting” based on biological data collected in 2004 and 2013 as part of the DNR/SHL stream REMAP and follow-up sampling projects.
This evaluated biological assessment was based on data collected in 2004 and 2013 as part of the DNR/SHL stream REMAP and follow-up sampling projects. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2004 FIBI score was 17 (poor) and the BMIBI score was 66 (good). The 2013 FIBI score was 23 (poor) and the BMIBI score was 57 (good). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41. This segment passed the FIBI BIC 0/2 times and passed the BMIBI BIC 2/2 times in the past 13 years. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 13 years (2004-2016); however, the multiple samples were not collected during a recent five-year period. According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s Section 303(d) list of impaired waters.