Assessment Comments
Assessment is based on (1) water quality monitoring conducted by LTRMP office, Bellevue, IA from 2000-04, (2) IDNR/UHL biocriteria sampling in 1999: FIBI = 17 (poor), BMIBI = 41 (fair). FIBI BIC = 36, BMIBI BIC = 51.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses are assessed (evaluated) as "partially supported" based on results of biological monitoring in 1999. Results of routine water quality monitoring conducted from 2002-2004, however, do not suggest problems with chemical / physical water quality. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream reach. The sources of data for this assessment include (1) results of IDNR/UHL biological monitoring near Teeds Grove in 1999 and (2) results of routine water quality monitoring conducted at station ER02.4 from 2002 through 2004 by IDNR staff of the Upper Mississippi River "Long-Term Resource Monitoring Program (LTRMP) at Bellevue, IA.
EXPLANATION: The assessment of the Class B(WW) uses is based on results of IDNR/LTRMP chemical/physical monitoring and IDNR/UHL biological monitoring. Results of the 1999 biocriteria sampling by IDNR and UHL show that the FIBI was "poor" (=17), while the BMIBI was only "fair" (=41). The aquatic life use support was assessed (evaluated) as partially supported (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51.
In addition to biological monitoring, this assessment is based on chemical/physical water quality data for 45 samples collected from Elk River at station ER02.4M during the period January 2002 through September 2004 as part of the Long-Term Resource Monitoring Program. Samples were collected approximately every two weeks; samples were collected during all months of the year. The parameters analyzed included dissolved oxygen, pH, ammonia-nitrogen, total phosphorus, total nitrogen, total suspended solids, and chlorophyll. A summary of these data show no violations of the Class B(WW) water quality criteria for temperature, pH, dissolved oxygen, or ammonia-nitrogen in the 45 samples collected.
Despite the results of chemical monitoring that suggest moderately good water quality in Elk River (at least in terms of compliance with Iowa Water Quality Standards), the results of biological monitoring suggest an impairment ("partial support") of the aquatic life uses. Because stream biota (fish and aquatic macroinvertebrates) integrate water quality impacts over the long-term, the results of biological monitoring are typically weighted more than results of chemical monitoring when determining support of aquatic life uses for purposes of Section 305(b) reporting. This approach is consistent with recommendations in U.S. EPA's guidelines for Section 305(b) reporting (see U.S. EPA 1997b, page 3-21). Thus, considering the "full support" suggested by results of chemical monitoring, and the "partial support" suggested by results of biological monitoring, the aquatic life use of this segment of Elk River are assessed as "partially supported" for the 2006 assessment/listing cycle. This assessment is consistent with results of previous biological monitoring that has suggested impairments to the aquatic life uses of this river segment.
Fish consumption uses remain "not assessed" due to the lack of monitoring in this stream reach.
