Assessment Comments
Assessment based on 1997 & 2003 IDNR/UHL biological monitoring data: FIBI = 51 (good), 20 (poor); BMIBI = 41 (fair). FIBI BIC = 33; BMIBI BIC = 41.
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 support level of the Class B(WW2) aquatic life uses was assessed as "partially supported" (minor impacts) based on 1997 and 2003 biological monitoring conducted as part of the IDNR/UHL stream biocriteria project.
EXPLANATION: The assessment of the Class B(WW2) aquatic life uses was based on data collected in 1997 and 2003 as part of the IDNR/UHL stream biocriteria project. The 1997 FIBI score was 51 (good) and the BMIBI score was 41 (fair). The 2003 FIBI score was 20 (poor) and the BMIBI score was not calculated due to the severe low number of organisms collected during the sampling. 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 FIBI BIC for this ecoregion is 33 and the BMIBI BIC is 41. This segment passed the FIBI BIC 1/2 times and passed the BMIBI BIC 1/1 times in the last 12 years.
This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years between 2004 and 2008 to be considered “monitored”. This segment had multiple FIBI samples collected in the previous 12 years (1997-2008); however, the multiple samples were not collected during 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).
In addition, this assessment was also categorized as "evaluated" because of the sampling conditions in 2003. This site is a reference site for the 40a ecoregion and has historically been assessed as "fully supporting". During the 2003 sampling visit, a bankfull/out of bank flood event less than one week prior, and was documented as a reason for the overall low aquatic abundance. From the 2003 Lick Creek field sheets: "Poor catch may be related to high (overbank) flow about a week prior to sampling. High (overbank) flows had occurred about a week prior to sampling. Much of the rock was clean (scoured & redeposited). Colonization was light in all habitats." This reference site will be sampled again in the near future.
