Assessment Comments
Assessment based on 2002 and 2012 IDNR/SHL biological sampling data: FIBI = 3 (poor), 30 (fair), BMIBI = 41, 47 (both fair) and on 2002 IDNR Fisheries data: FIBI = 23 (poor). FIBI BIC = 31, BMIBI BIC = 54.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.gov/Portals/idnr/uploads/water/standards/files/swcdoc2.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY/EXPLANATION: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.
The Class B(WW2) aquatic life uses are assessed (evaluated) as "partially supporting" (IR 5b-t) based on data collected in 2002 and 2012 as part of the IDNR/SHL stream REMAP and follow-up sampling projects and on data collected in 2002 as part of a IDNR Fisheries stream sampling project: Cold Springs Fish Management. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were 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 2002 REMAP FIBI score was 30 (fair) and the BMIBI score was 47 (fair). The 2002 IDNR Fisheries FIBI score was 23 (poor). The 2012 FIBI score was 3 (poor) and the BMIBI score was 41 (fair). 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 biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54. This segment passed the FIBI BIC 0/3 times and passed the BMIBI BIC 0/3 times in the last 11 years.
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 IDNR’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). IDNR 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 was previously on Iowa’s Section 303(d) list and thus remains on Iowa’s Section 303(d) list of impaired waters (IR Category 5b-t).
Data from the physical habitat assessment and 3 grab water samples collected for the REMAP project did not identify a specific cause of impairment. Additional sampling data are needed to assess the current status of aquatic life uses and causes/sources of impairment.
