Silver Creek IA 05-NSH-1452
from Hwy 41 (NW 1/4 S5 T71N R41W Mills Co.) to Middle Silver Cr. is S31 T74N R41W Pottawattamie Co.
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 as part of the 2006 DNR/SHL stream REMAP project.
The Class B(WW2) aquatic life uses remain assessed (evaluated) as “partially supporting based on biological data collected in 2006 as part of the DNR/SHL stream REMAP project. 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 2006 FIBI score was 18 (poor) and the BMIBI score was 49 (fair). The aquatic life use support was assessed (evaluated) 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 31 and the BMIBI BIC for this ecoregion is 54. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. This segment failed the FIBI BIC and passed the BMIBI BIC (using the BMIBI UAV of 8 points) in 2006. This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over 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). Also, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). 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). Therefore, despite this change in assessment methodology and type, this waterbody remains in IR Category 3b-c and is considered a water in need of further investigation.