Assessment Comments
Assessment remains based on biological monitoring conducted by the IDNR Fisheries Bureau in 1999 and 2001.
Basis for Assessment
[Note: Prior to the current (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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY/EXPLANATION: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.
This is the same assessment of aquatic life uses as that developed for the previous (2004 and 2006) assessment cycles. The Class B(WW2) aquatic life uses remain assessed as “impaired”, and this waterbody has been included in Category 5 of Iowa’s 2008 Integrated Report. 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).
The assessment of the Class B(WW2) aquatic life uses remains based on data collected in 1999 and 2001 as part of a DNR Fisheries stream sampling project: Chariton 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 1999-2001 evaluated Fish IBI average (n=2) was 18 (poor). The aquatic life use support was assessed (evaluated) as Not Supporting (=NS), 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 from 1999-2002. 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).
