Assessment Comments

Historic assessments based on 2001 Fisheries data.

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 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 assessment of the Class B(WW2) aquatic life uses is changed from (evaluated) as “fully supported” (IR 2a) to “not assessed” (IR 3a) due to the age of the data upon which the original assessment was based.   The source of data for this assessment remains the results of biological monitoring by the IDNR Fisheries Bureau in 2001.  

EXPLANATION:  For previous assessments, the Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported” based on data collected in 2001 as part of an IDNR Fisheries stream sampling project: Manchester research station.   A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the Fisheries sampling data.   The biological metrics are based on the numbers and types of 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).   The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2001 evaluated FIBI was 53 (good).   The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI score 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 1994-2008.   The non-riffle site FIBI BIC for this ecoregion is 44.   This segment passed the FIBI BIC 1/1 times in 2001.   For the 2010 and 2012 assessment cycles, this aquatic life assessment was considered "evaluated" based on a change in the 2010 IDNR assessment methodology that required a segment to have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”.   This segment had a single sample collected in 2001.   Additionally, because these data were considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category was considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).   Despite this change in assessment methodology and type, this waterbody remained in IR Category 2a.

The previous (2012) assessment of the Class B(WW2) aquatic life uses is changed from (evaluated) “fully supporting” to “not assessed” due to age of the data upon which the assessment was based.   Because the data upon which these assessment were based are now more than ten years old, the Class B(WW2) uses are now considered “not assessed.”  As water quality data age, they are less able to represent current water quality conditions.   As data age beyond ten years, their ability to represent current water quality conditions is increasing suspect.   Additional biological monitoring is needed in this assessment segment to update status of its aquatic communities.