Assessment Comments
Assessment based on results of (1) IDNR/UHL ambient monthly water quality monitoring near Riverside from 2000-02 and (2) IDNR/UHL biological sampling from 1999-2002.
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses were assessed (monitored) as "fully supporting / threatened" based on results of (1) ambient water quality monitoring that show single violations of water quality criteria for lead and chlorpyrifos and (2) results of biological monitoring that show somewhat low biotic index values for the fish and macroinvertebrate communities. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this river segment. The assessments of support of beneficial uses are based (1) on results of IDNR/UHL ambient monthly-plus water quality monitoring conducted on the English River near Riverside during the 2000-2002 assessment period (station 10920001), (2) results of IDNR/UHL daily monitoring for dissolved oxygen and temperature from May through July 2000, and (3) results of IDNR/UHL biological monitoring conducted from 1999-2002.
EXPLANATION: None of the 49 samples collected during the 2000-2002 assessment period violated Class B(WW) water quality criteria for pH or ammonia-nitrogen; none of the 138 samples violated the Class B(WW) criterion for dissolved oxygen (this station was sampled daily from May through July 2000). One of the 138 samples violated the Class B(WW) criterion for temperature: the water temperature in the sample collected on August 1, 2002 was 32.3C, thus slightly above the water quality standard of 32C. Violations also occurred, however, for Class B(WW) criteria for toxic metals and for pesticides. One of the four samples analyzed for toxic metals exceeded the Class B(WW) chronic criterion for lead. The sample collected on July 5, 2000, contained 50 ppb of lead, thus exceeding the Class B(WW) chronic criterion of 30 ppb. Similarly, one of the 19 samples analyzed for pesticides exceeded Class B(WW) criteria. The sample collected on June 15, 2001, contained 0.053 ppb of chlorpyrifos; this level exceeds the Class B(WW) chronic criterion of 0.041 ppb. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), this single violation of chronic criteria for lead and chlorpyrifos do not suggest an impairment of aquatic life uses. Based on DNR's assessment methodology for Section 305(b) reporting, however, these violations suggest that the Class B(WW) aquatic life uses should be assessed as "fully supported/threatened." The occurrence of a violation of the Class B(WW) chronic criterion for chlorpyrifos during the previous (1998-1999) biennial period (see assessment for the 2000 report above) suggests a potential impairment due to this pesticide. Additional monitoring should be conducted to better characterize the levels of chlorpyrifos in this river segment and to better determine whether an impairment of aquatic life uses may exist.
The assessment based on results of biological monitoring are consistent with the assessment based on results of IDNR/UHL chemical/physical monitoring. Biological data were collected in 1999, 2000, 2001, and 2002 as part of the ambient monitoring project and the DNR/UHL stream biocriteria 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 2001 Fish IBI score was 33 (fair). The 1999, 2000, 2001, and 2002 BM-IBI scores were 54 (fair), 56 (good), 51 (fair), and 45 (fair) respectively. The aquatic life use support was assessed as fully supporting/threatened (=FST), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001.
The fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this river segment.
