Assessment Comments
Assessment based on 1998 Fisheries data: Fish IBI = 29 (fair).
Basis for Assessment
[Note: Although originally placed in Category 3b of Iowa's 2004 Integrated Report by Iowa DNR, U.S. EPA Region VII, in their May 23, 2006 transmittal of Iowa's final approved 2004 Section 303(d) list, added this waterbody segment to Iowa's 2004 Section 303(d) list (IR Category 5b). Iowa DNR maintained that addition of this assessment segment to Iowa’s 2004 Section 303(d) list was inappropriate. That is, the bioassessment data generated by the IDNR Fisheries Bureau for this assessment segment lacked the necessary documentation or metadata to determine whether the data meet quality and completeness criteria required of higher confidence (i.e., “monitored”) assessments that IDNR considers appropriate for Section 303(d) listing. Thus, the assessment type was considered of lower confidence (i.e., "evaluated"), and thus this "partially supported" waterbody was considered not appropriate for Section 303(d) listing. U.S. EPA Region VII, however, based on their review of the IDNR Fisheries bioassessment data for this assessment segment, concluded that these data are, in fact, scientifically adequate and representative of current water quality. Thus, EPA added-back this assessment segment to Iowa's 2004 final approved Section 303(d) list (Category 5b). Iowa DNR’s original assessment for the 2004 Section 305(b) assessment cycle is included below.]
The assessment was based on data collected in 1998 as part of a DNR 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 (F-IBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 evaluated Fish IBI was 29 (fair). The aquatic life use support was assessed (evaluated) as Partially Supporting (=PS), based on a comparison of the F-IBI score with biological assessment criteria established for previous Section 305(b) reports. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
The sample data from this segment lack the necessary documentation or metadata to determine whether the data meet quality and completeness criteria required of “monitored” assessments. Thus, FIBI scores calculated from IDNR Fisheries Bureau sampling data collected in this segment provide useful, but limited evidence of impairment. With respect to FIBI sample results, the following criteria are considered: sampling conditions; sampling gear; crew size; and length of stream sampled. One or more of these sample descriptors are not available for the Fisheries Bureau data. Therefore, IDNR considers the aquatic life use impairments indicated by these data as “evaluated” assessments and thus as not appropriate for Section 303(d) listing (Category 5). IDNR does, however, consider these impairments as appropriate for listing under Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).
