Fox River IA 04-FOX-995

Assessment Comments

Assessment is based on results of (1) USGS monitoring in 1998 and 1999 near Bloomfield, West Grove and Paris and (2) UHL biological monitoring near Pulaski and West Grove in 1998.

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses were assessed as "not supported."  EXPLANATION:  The biological data used to develop the assessment for the 1998 report (see above) were collected in 1990 and are now considered too old (greater than five years) to be useful for assessing current water quality conditions.   For the 2000 assessment, the 44-mile Fox River waterbody segment (IA 04-FOX-0010-0) was divided into two subsegments (IA 04-FOX-0010-1 and IA 04-FOX-0010-2) of approximately equal length.   Results of water quality monitoring from two sources were used to develop the current assessment of support of the Class B(LR) uses:  (1) chemical water quality monitoring conducted in 1998 and 1999 by the U.S.  Geological Survey at three stations (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) and (2) biological monitoring conducted near Pulaski and West Grove in Davis County in October 1998 by the University of Iowa Hygienic Laboratory (see Luzier and Miller 1999).   The West Grove and Paris stations are located near the upstream boundary of this Class B(LR) segment.   USGS monitoring in 1998 and 1999 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."  Although not designated for Class C (drinking water) uses, from 30 to 40 percent of the 10 samples from each station analyzed for pesticides during the 1998-1999 period exceeded the U.S.  EPA MCL of 3.0 ug/l.   None of the 12 samples at collected at each station exceeded the nitrate MCL of 10.0 mg/l.   Results of biological monitoring in 1998 by UHL showed moderately diverse fish communities for streams in the Central Irregular Plains ecoregion, with 14 species from 4 families at the Paluski station and 13 species from 5 families at the West Grove station.   These sites contained all (9 of 9 at Pulaski) or nearly all (8 of 9 at West Grove) of the expected fish taxa for Class B(LR) streams in this ecoregion.   Based on DNR's assessment methodology for Section 305(b) reporting, the composition of the fish community suggests that the Class B(LR) uses are "fully supported."  However, based on results of chemical water quality monitoring 1998-1999 biennial period that show repeated violations of state water quality criteria for dissolved oxygen and ammonia-nitrogen, the Class B(LR) aquatic life uses of this stream reach are assessed as "not supported."