Assessment Comments
Assessment remains based on 2000 IDNR/UHL biological monitoring data: FIBI = 15 (poor); BMIBI = 56 (good) and on 2000 Fisheries data: FIBI = 51 (good). Non-riffle habitat FIBI BIC = 32, BMIBI BIC = 62.
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.com/water/standards/files/06mar_swc.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 (2010) 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 (biocriteria) sampling in 2000. The 2000 sampling data are now greater than five years old; therefore, this assessment is now considered "evaluated" instead of "monitored". Due to the previous (2004; 2006) Section 303(d) impairment of aquatic life uses, however, this assessment segment remains in Category 5b of Iowa's 2010 Integrated Report.
EXPLANATION: The assessment of the Class B(WW2) aquatic life uses was based on data collected in 2000 at the Michaelson Marsh Area (Kossuth Co.) as part of the IDNR/UHL stream biocriteria project and on data collected in 2000 as part of a DNR Fisheries stream sampling project: Manchester research station.. The 2000 FIBI scores were 15 (poor) and 51 (good) and the BMIBI score was 56 (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 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 32 and the BMIBI BIC for this ecoregion is 62.
This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years from 2004-2008. 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 remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.
