Assessment Comments
Evaluated assessment remains based on 2006 IDNR/SHL stream REMAP data: FIBI = 14 (poor), BMIBI = 52 (fair). FIBI BIC = 43; BMIBI BIC = 54.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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 also now presumptively designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY: 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(WW1) aquatic life uses remain assessed (evaluated) as “partially supported” (IR Category 3b-u) based on results of biological sampling in 2006. The source of data for this assessment is the results of IDNR/SHL biological sampling conducted in 2006 as part of the stream REMAP project. Previous assessments were also based on results of IDNR/SHL ambient water quality monitoring conducted during the 2000-2001 biennial period south of Turin in Monona Co. at STORET station 10670001 (formerly station 911090) (note: the IDNR/SHL ambient monitoring station south of Turin was dropped from the IDNR monitoring network after September 2000). These data are now considered too old (greater than 10 years) to be useful for characterizing current water quality conditions.
EXPLANATION: The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supporting" based on data collected in 2006 as part of the IDNR/SHL stream REMAP project. A series of biological metrics that 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 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 14 (poor) and the BMIBI score was 52 (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 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 assessment is considered evaluated because the drainage area (912 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed the BMIBI BIC (using the UAV of 8 points) and failed to meet the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size. 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).
Fish consumption uses remain "not assessed" due to the lack of recent fish contaminant monitoring in this river segment.
