Assessment Comments
Assessment remains based on results of IDNR/UHL biological (biocriteria) monitoring in 1998: FIBI scores = 20, 24 (both poor) and 32, 37 (both fair). FIBI average = 28 (fair). FIBI BIC = 33.
Basis for Assessment
[Note: Prior to the current (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 (2008) 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: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life are assessed (evaluated) as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 1998. The biological monitoring data are now greater than five years old; therefore, this assessment is now considered "evaluated" instead of "monitored". All of the FIBI scores increased compared to what was reported in previous Section 305(b) reports but the segments is still not meeting Biological Impairment Criteria. Prior to the 2008 Section 305(b) assessment cycle, the FIBI scores were calculated using erroneous data.
EXPLANATION: The evaluated biological assessment of the aquatic life uses was based on data collected in 1998 as part of the IDNR/UHL stream REMAP project. A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1998 FIBI scores were 20, 24 (both poor) and 32, 37 (both fair). The FIBI average was 28 (fair). The aquatic life use support was assessed (evaluated) as Partially Supporting (=PS), 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 failed to meet 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.
