Assessment Comments
Assessment based on 2004, 2012 and 2013 IDNR/SHL biological sampling data: CBI = 41, 47 and 61; CW BIC = 60.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(CW) 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 also now presumptively designated for Class A1 (primary contact recreation) and Class A2 (secondary contact recreation) uses. This segment remains designated for coldwater aquatic life use (now termed Class B(CW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption) uses.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses and the presumptive Class A2 (secondary contact recreation) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment. The Class B(CW1) coldwater aquatic life uses are assessed (evaluated) as "partially supported" (IR 5b-t) based on results of biological monitoring in 2004, 2012 and 2013. Fish consumption uses remain "not assessed" (IR 3a).
EXPLANATION: The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2004, 2012 and 2013 as part of the IDNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2007 CBI score was 41, the 2012 score was 61 and the 2013 score was 47. The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the CBI score with biological impairment criteria (BIC) established for the 2012 Section 305(b) report. The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011. The CW BIC is 60 and this segment passed the CW BIC 1/3 times in the last 10 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 2008 and 2012 to be considered “monitored”. This assessment used multiple samples collected in the previous 10 years (2004-2013) because the two samples that were collected in 2012/2013 could not complete the assessment (one passed, one failed). 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). Despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s 2012 Section 303(d) list of impaired waters.
This site is approximately 1/10th of a mile from the upper end of the cold water segment. At this time, IDNR does not know if the spring is above or below the sampling site and if the sampling data should be judged on a cold or warm water basis. The information below is an additional assessment based on warm water criteria.
The additional assessment of the aquatic life uses based on data collected in 2012 and 2013 as part of an IDNR/SHL sampling project. 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 2012 FIBI score was 76 (excellent) and the BMIBI score was 85 (excellent). The 2013 FIBI score was 79 (excellent) and the BMIBI score was 75 (good). If the segment was designated warm water, the aquatic life use support would be assessed (monitored) as fully supporting (=FS), based on a comparison of the FIBI score 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 62 and the BMIBI BIC is 61.
Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.
