Assessment Comments
Assessment remains based on 2001 IDNR/UHL biological monitoring data: FIBI = 52 (good), BMIBI = 60 (good). Non-riffle habitat FIBI BIC = 44; natural substrate BMIBI BIC = 70.
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, 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 (2012) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: 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(WW-2) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of IDNR/UHL biological monitoring conducted in 2001. The 2001 sampling data are now greater than five years old; therefore, this assessment is now considered "evaluated" instead of "monitored".
EXPLANATION: The Class B(WW2) aquatic life uses remain assessed (evaluated) as “partially supporting” based on data collected in 2001 as part of the IDNR/UHL stream biocriteria project. The 2001 FIBI score was 52 (good) and the BMIBI score was 60 (good). 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 biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The non-riffle habitat FIBI BIC for this ecoregion is 44 and the natural substrate BMIBI BIC for this ecoregion is 70.
This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over a five-year period. Additionally, 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). 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 placed in IR Category 5b and thus remains on Iowa’s Section 303(d) list of impaired waters.
