Assessment Comments
Assessment based on: (1) 2002 REMAP data: Fish IBI= 22 (poor), BM-IBI= 25 (poor); (2) USGS monitoring in 1998 and 1999 near Bloomfield, West Grove and Paris and (3) UHL biological monitoring near Pulaski and West Grove in 1998.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed as "not supported" based on results of IDNR/UHL biological and (continuous) water quality monitoring conducted as part of the REAMP project in 2002. Results of water quality monitoring conducted by USGS in 1998 and 1999 support this assessment.
EXPLANATION: The assessment was updated based on data collected in 2002 as part of the DNR/UHL REMAP project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and 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) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 Fish IBI score was 22 (poor) and the BM-IBI score was 25 (poor). The aquatic life use support was assessed as not supporting (=NS), based on a comparison of the F-IBI and BM-IBI scores 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.
As part of the REMAP project, diurnal dissolved oxygen and temperature monitoring conducted during July 2002 found d.o. levels sagging to approx. 4.2 mg/L during night hours. Additional sampling data are needed to evaluate the extent, causes and sources of this water quality problem. Stream physical habitat assessment found excessive sediment deposits and a lack of instream cover that could also contribute to the biological impairment. The wide-shallow channel probably contributes to observed high stream temperature (>36C) and high rates of biological community respiration and primary production.
Previous Section 305(b) assessments suggest that chemical water quality may be a cause of the low biotic index values seen in REMAP monitoring. The following is summarized the assessment developed for the 2000 reporting cycle (see the assessment developed for the 2000 reporting cycle for the full assessment):
Results of chemical water quality monitoring conducted in 1998 and 1999 by the U.S. Geological Survey at three stations on this segment of the Fox River (Bloomfield (S27, T69N, R13W), West Grove (NW1/4, S27, T69N, R15W), and Paris (NE1/4, S24, T69N, R15W)) (see May et al. 1999 and Nalley et al. 2000) showed no violations of Class B(LR) water quality criteria for dissolved oxygen, pH, and ammonia-nitrogen in the 12 samples collected at the Bloomfield or Paris stations. At the West Grove (most upstream) station, however, two of 12 samples violated the Class B(LR) criterion for dissolved oxygen, and three of 12 samples violated Class B(LR) chronic criteria for ammonia-nitrogen. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the percentage of violations of the dissolved oxygen criterion (17%) indicates that the Class B(LR) uses are only "partially supported." According to these same guidelines (U.S. EPA 1997b, page 3-18), the three violations (25%) of chronic criteria for ammonia-nitrogen indicate "nonsupport" of the Class B(LR) uses. Of the 12 samples analyzed for toxic metals, one sample at each station exceeded a state water quality criterion. The samples collected at all three stations on June 10, 1999, exceeded the Class B(LR) chronic water quality criterion for copper (55 ug/l): the level at Bloomfield was 120 ug/l, at Paris 90 ug/l, and at West Grove 110 ug/l. These samples were collected during a high flow event on the Fox River; the June 10 stream flow was 599 cfs at Bloomfield. 1,140 at Paris, and 1,170 cfs at the West Grove station. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), a single violation of a criterion for a toxic contaminant does not suggest an impairment of the aquatic life uses. Based on DNR's assessment methodology for Section 305(b) reporting, however, this violation suggests that the Class B(LR) aquatic life uses should be assessed as "fully supported / threatened."
