Assessment Comments
Assessment is based on (1) results of IDNR/UHL biological (biocriteria) monitoring in 2001: 6 of 8 coldwater biological indicators met the criteria (= Fully Supporting/Threatened (FS/T)) and (2) a summary of trout reproduction in Iowa streams prepared by IDNR Fisheries in 2002.
Basis for Assessment
SUMMARY: The Class B(CW) coldwater aquatic life uses remain assessed (monitored) as "fully supported / threatened" (minor impacts) based on (1) biological (biocriteria) sampling conducted in 2001 and (2) a summary of trout reproduction in Iowa streams prepared by the IDNR Fisheries Bureau in 2002. The assessment type is considered "monitored" (high confidence assessment) based on existence of two separate assessments that both indicate the same result ("fully supported / threatened" (minor impacts)). Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment.
EXPLANATION: The assessment of the Class B(CW) aquatic life uses was based on data collected in 2001 as part of the DNR/UHL stream biocriteria project. A series of eight (8) coldwater biological indicators, which reflect stream water quality and habitat integrity, were calculated from the biocriteria sampling data and supplemental IDNR Fisheries Bureau data. The coldwater biological indicators are based on the numbers and types of coldwater benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. According to the IDNR methodology, sites that score 7 or 8 are Fully Supporting (FS), sites that score 4-6 are Fully Supporting/Threatened (FS/T), sites that score 2-3 are Partially Supporting (PS), and sites that score 0-1 are Not Supporting (NS). The 2001 coldwater biological indicator score was 6 of 8; thus, the aquatic life use support was assessed as Fully Supporting/Threatened (=FS/T), based on a comparison of the coldwater biological indicator score with biological assessment criteria established for this Section 305(b) report. The coldwater biological indicators were determined from a statistical analysis of data collected at coldwater stream ecoregion reference sites from 1994-2002 and with assistance from the IDNR Fisheries Bureau.
In addition to results of IDNR/UHL biological monitoring, an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in April 2002 also suggests that the Class B(CW) uses should be assessed as "fully supported / threatened." According to the updated summary, this reach of Burr Oak Creek is in the category of Iowa trout streams that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population for the target trout species at this time.
Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.
