Heather Branch IA 03-SKU-901

Assessment Comments

Assessment remains based on 1998 IDNR/UHL biological monitoring data: FIBI = 72 (good). FIBI BIC = 33.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general 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 and for Class B(WW1) aquatic life uses.   According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters.   Thus, for the current (2010) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]

SUMMARY/EXPLANATION:  The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological monitoring in 1998.   The assessment type is considered "evaluated" (relatively lower confidence assessment) due to the uncertainty of using biological assessment methods developed for larger, wadeable streams for assessing aquatic life conditions in small headwater stream segments.   Note:  the data from the 1998 biological sampling are approximately 10 years old and are thus of questionable utility for assessing current water quality and biological conditions.   Lacking any more recent data, the aquatic life uses of this stream segment will be considered “not assessed” for the next (2012) and future assessment/listing cycles.

EXPLANATION:  The aquatic life uses remain assessed as "fully supported" based on results of the IDNR/UHL biological monitoring conducted on this stream segment in 1998.   As stated in the assessment for the 2000 reporting cycle, only fish data were collected and analyzed; the FIBI score was 72 (good).   The aquatic life use support status was assessed (evaluated) 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 1994-2004.   The FIBI BIC for this ecoregion is 33.   Even though this site passed the FIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.